Add support for GFM footnotes

1 files changed, 1530 insertions, 0 deletions

diff --git a/tests/gfm_footnote.rs b/tests/gfm_footnote.rs
new file mode 100644
index 0000000..8c6cc54
--- /dev/null
+++ b/tests/gfm_footnote.rs
@@ -0,0 +1,1530 @@
+extern crate micromark;
+use micromark::{micromark, micromark_with_options, Constructs, Options};
+use pretty_assertions::assert_eq;
+
+#[test]
+fn gfm_footnote() {
+    let gfm = Options {
+        constructs: Constructs::gfm(),
+        ..Options::default()
+    };
+
+    assert_eq!(
+        micromark("A call.[^a]\n\n[^a]: whatevs"),
+        "<p>A call.<a href=\"whatevs\">^a</a></p>\n",
+        "should ignore footnotes by default"
+    );
+
+    assert_eq!(
+        micromark_with_options("A call.[^a]\n\n[^a]: whatevs", &gfm),
+        "<p>A call.<sup><a href=\"#user-content-fn-a\" id=\"user-content-fnref-a\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-a\">
+<p>whatevs <a href=\"#user-content-fnref-a\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support footnotes"
+    );
+    assert_eq!(
+        micromark_with_options(
+            "Noot.[^a]\n\n[^a]: dingen",
+            &Options {
+                constructs: Constructs::gfm(),
+                gfm_footnote_label: Some("Voetnoten".to_string()),
+                gfm_footnote_back_label: Some("Terug naar de inhoud".to_string()),
+                ..Options::default()
+            }
+        ),
+        "<p>Noot.<sup><a href=\"#user-content-fn-a\" id=\"user-content-fnref-a\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Voetnoten</h2>
+<ol>
+<li id=\"user-content-fn-a\">
+<p>dingen <a href=\"#user-content-fnref-a\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Terug naar de inhoud\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support `options.gfm_footnote_label`, `options.gfm_footnote_back_label`"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            "[^a]\n\n[^a]: b",
+            &Options {
+                constructs: Constructs::gfm(),
+                gfm_footnote_label_tag_name: Some("h1".to_string()),
+                ..Options::default()
+            }
+        ),
+        "<p><sup><a href=\"#user-content-fn-a\" id=\"user-content-fnref-a\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h1 id=\"footnote-label\" class=\"sr-only\">Footnotes</h1>
+<ol>
+<li id=\"user-content-fn-a\">
+<p>b <a href=\"#user-content-fnref-a\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support `options.gfm_footnote_label_tag_name`"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            "[^a]\n\n[^a]: b",
+            &Options {
+                constructs: Constructs::gfm(),
+                gfm_footnote_label_attributes: Some("class=\"footnote-heading\"".to_string()),
+                ..Options::default()
+            }
+        ),
+        "<p><sup><a href=\"#user-content-fn-a\" id=\"user-content-fnref-a\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"footnote-heading\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-a\">
+<p>b <a href=\"#user-content-fnref-a\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support `options.gfm_footnote_label_attributes`"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            "[^a]\n\n[^a]: b",
+            &Options {
+                constructs: Constructs::gfm(),
+                gfm_footnote_clobber_prefix: Some("".to_string()),
+                ..Options::default()
+            }
+        ),
+        "<p><sup><a href=\"#fn-a\" id=\"fnref-a\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"fn-a\">
+<p>b <a href=\"#fnref-a\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support `options.gfm_footnote_clobber_prefix`"
+    );
+
+    assert_eq!(
+        micromark_with_options("A paragraph.\n\n[^a]: whatevs", &gfm),
+        "<p>A paragraph.</p>\n",
+        "should ignore definitions w/o calls"
+    );
+
+    assert_eq!(
+        micromark_with_options("a[^b]", &gfm),
+        "<p>a[^b]</p>",
+        "should ignore calls w/o definitions"
+    );
+
+    assert_eq!(
+        micromark_with_options("a[^b]\n\n[^b]: c\n[^b]: d", &gfm),
+        "<p>a<sup><a href=\"#user-content-fn-b\" id=\"user-content-fnref-b\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-b\">
+<p>c <a href=\"#user-content-fnref-b\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should use the first of duplicate definitions"
+    );
+
+    assert_eq!(
+        micromark_with_options("a[^b], c[^b]\n\n[^b]: d", &gfm),
+        "<p>a<sup><a href=\"#user-content-fn-b\" id=\"user-content-fnref-b\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>, c<sup><a href=\"#user-content-fn-b\" id=\"user-content-fnref-b-2\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup></p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-b\">
+<p>d <a href=\"#user-content-fnref-b\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a> <a href=\"#user-content-fnref-b-2\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩<sup>2</sup></a></p>
+</li>
+</ol>
+</section>
+",
+        "should supports multiple calls to the same definition"
+    );
+
+    assert_eq!(
+        micromark_with_options("![^a](b)", &gfm),
+        "<p>!<a href=\"b\">^a</a></p>",
+        "should not support images starting w/ `^` (but see it as a link?!, 1)"
+    );
+
+    assert_eq!(
+        micromark_with_options("![^a][b]\n\n[b]: c", &gfm),
+        "<p>!<a href=\"c\">^a</a></p>\n",
+        "should not support images starting w/ `^` (but see it as a link?!, 2)"
+    );
+
+    assert_eq!(
+        micromark_with_options("[^]()", &gfm),
+        "<p><a href=\"\">^</a></p>",
+        "should support an empty link with caret"
+    );
+
+    assert_eq!(
+        micromark_with_options("![^]()", &gfm),
+        "<p>!<a href=\"\">^</a></p>",
+        "should support an empty image with caret (as link)"
+    );
+
+    // <https://github.com/github/cmark-gfm/issues/239>
+    assert_eq!(
+        micromark_with_options("Call.[^a\\+b].\n\n[^a\\+b]: y", &gfm),
+        "<p>Call.<sup><a href=\"#user-content-fn-a%5C+b\" id=\"user-content-fnref-a%5C+b\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-a%5C+b\">
+<p>y <a href=\"#user-content-fnref-a%5C+b\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support a character escape in a call / definition"
+    );
+
+    assert_eq!(
+        micromark_with_options("Call.[^a&copy;b].\n\n[^a&copy;b]: y", &gfm),
+        "<p>Call.<sup><a href=\"#user-content-fn-a&amp;copy;b\" id=\"user-content-fnref-a&amp;copy;b\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-a&amp;copy;b\">
+<p>y <a href=\"#user-content-fnref-a&amp;copy;b\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support a character reference in a call / definition"
+    );
+
+    // <https://github.com/github/cmark-gfm/issues/239>
+    // <https://github.com/github/cmark-gfm/issues/240>
+    assert_eq!(
+        micromark_with_options("Call.[^a\\]b].\n\n[^a\\]b]: y", &gfm),
+        "<p>Call.<sup><a href=\"#user-content-fn-a%5C%5Db\" id=\"user-content-fnref-a%5C%5Db\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-a%5C%5Db\">
+<p>y <a href=\"#user-content-fnref-a%5C%5Db\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support a useful character escape in a call / definition"
+    );
+
+    assert_eq!(
+        micromark_with_options("Call.[^a&#91;b].\n\n[^a&#91;b]: y", &gfm),
+        "<p>Call.<sup><a href=\"#user-content-fn-a&amp;#91;b\" id=\"user-content-fnref-a&amp;#91;b\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-a&amp;#91;b\">
+<p>y <a href=\"#user-content-fnref-a&amp;#91;b\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support a useful character reference in a call / definition"
+    );
+
+    assert_eq!(
+        micromark_with_options("Call.[^a\\+b].\n\n[^a+b]: y", &gfm),
+        "<p>Call.[^a+b].</p>\n",
+        "should match calls to definitions on the source of the label, not on resolved escapes"
+    );
+
+    assert_eq!(
+        micromark_with_options("Call.[^a&#91;b].\n\n[^a\\[b]: y", &gfm),
+        "<p>Call.[^a[b].</p>\n",
+        "should match calls to definitions on the source of the label, not on resolved references"
+    );
+
+    assert_eq!(
+        micromark_with_options("[^1].\n\n[^1]: a\nb", &gfm),
+        "<p><sup><a href=\"#user-content-fn-1\" id=\"user-content-fnref-1\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-1\">
+<p>a
+b <a href=\"#user-content-fnref-1\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support lazyness (1)"
+    );
+
+    assert_eq!(
+        micromark_with_options("[^1].\n\n> [^1]: a\nb", &gfm),
+        "<p><sup><a href=\"#user-content-fn-1\" id=\"user-content-fnref-1\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<blockquote>
+</blockquote>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-1\">
+<p>a
+b <a href=\"#user-content-fnref-1\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support lazyness (2)"
+    );
+
+    assert_eq!(
+        micromark_with_options("[^1].\n\n> [^1]: a\n> b", &gfm),
+        "<p><sup><a href=\"#user-content-fn-1\" id=\"user-content-fnref-1\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<blockquote>
+</blockquote>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-1\">
+<p>a
+b <a href=\"#user-content-fnref-1\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+",
+        "should support lazyness (3)"
+    );
+
+    assert_eq!(
+        micromark_with_options("[^1].\n\n[^1]: a\n\n    > b", &gfm),
+        "<p><sup><a href=\"#user-content-fn-1\" id=\"user-content-fnref-1\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-1\">
+<p>a</p>
+<blockquote>
+<p>b</p>
+</blockquote>
+<a href=\"#user-content-fnref-1\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a>
+</li>
+</ol>
+</section>
+",
+        "should support lazyness (4)"
+    );
+
+    // 999 `x` characters.
+    let max = "x".repeat(999);
+
+    assert_eq!(
+        micromark_with_options(format!("Call.[^{}].\n\n[^{}]: y", max, max).as_str(), &gfm),
+        format!("<p>Call.<sup><a href=\"#user-content-fn-{}\" id=\"user-content-fnref-{}\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">1</a></sup>.</p>
+<section data-footnotes=\"\" class=\"footnotes\"><h2 id=\"footnote-label\" class=\"sr-only\">Footnotes</h2>
+<ol>
+<li id=\"user-content-fn-{}\">
+<p>y <a href=\"#user-content-fnref-{}\" data-footnote-backref=\"\" class=\"data-footnote-backref\" aria-label=\"Back to content\">↩</a></p>
+</li>
+</ol>
+</section>
+", max, max, max, max),
+        "should support 999 characters in a call / definition"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            format!("Call.[^a{}].\n\n[^a{}]: y", max, max).as_str(),
+            &gfm
+        ),
+        format!("<p>Call.[^a{}].</p>\n<p>[^a{}]: y</p>", max, max),
+        "should not support 1000 characters in a call / definition"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"a![i](#)
+a\![i](#)
+a![i][]
+a![^1]
+[^1]
+^1]
+
+[^1]: b
+
+[i]: c"###,
+            &gfm
+        ),
+        r###"<p>a<img src="#" alt="i" />
+a!<a href="#">i</a>
+a<img src="c" alt="i" />
+a!<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup>
+<sup><a href="#user-content-fn-1" id="user-content-fnref-1-2" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup>
+^1]</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>b <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a> <a href="#user-content-fnref-1-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩<sup>2</sup></a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match bang/caret interplay like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options("a![^1]", &gfm),
+        "<p>a![^1]</p>",
+        "should match bang/caret interplay (undefined) like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"a![^1]
+
+[^1]: b
+"###,
+            &gfm
+        ),
+        r###"<p>a!<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup></p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>b <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match bang/caret like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Calls may not be empty: [^].
+
+Calls cannot contain whitespace only: [^ ].
+
+Calls cannot contain whitespace at all: [^ ], [^	], [^
+].
+
+Calls can contain other characters, such as numbers [^1234567890], or [^^]
+even another caret.
+
+[^]: empty
+
+[^ ]: space
+
+[^	]: tab
+
+[^
+]&#x3A; line feed
+
+[^1234567890]: numbers
+
+[^^]: caret
+"###,
+            &gfm
+        ),
+        r###"<p>Calls may not be empty: <a href="empty">^</a>.</p>
+<p>Calls cannot contain whitespace only: <a href="empty">^ </a>.</p>
+<p>Calls cannot contain whitespace at all: <a href="empty">^ </a>, <a href="empty">^	</a>, <a href="empty">^
+</a>.</p>
+<p>Calls can contain other characters, such as numbers <sup><a href="#user-content-fn-1234567890" id="user-content-fnref-1234567890" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup>, or <sup><a href="#user-content-fn-%5E" id="user-content-fnref-%5E" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup>
+even another caret.</p>
+<p><a href="empty">^
+</a>: line feed</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1234567890">
+<p>numbers <a href="#user-content-fnref-1234567890" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-%5E">
+<p>caret <a href="#user-content-fnref-%5E" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match calls like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^*emphasis*]
+
+[^**strong**]
+
+[^`code`]
+
+[^www.example.com]
+
+[^https://example.com]
+
+[^://example.com]
+
+[^[link](#)]
+
+[^![image](#)]
+
+[^*emphasis*]: a
+
+[^**strong**]: a
+
+[^`code`]: a
+
+[^www.example.com]: a
+
+[^https://example.com]: a
+
+[^://example.com]: a
+
+[^[link](#)]: a
+
+[^![image](#)]: a
+"###,
+            &gfm
+        ),
+        // Note:
+        // * GH does not support colons.
+        //   See: <https://github.com/github/cmark-gfm/issues/250>
+        //   Here identifiers that include colons *do* work (so they’re added below).
+        // * GH does not support footnote-like brackets around an image.
+        //   See: <https://github.com/github/cmark-gfm/issues/275>
+        //   Here images are fine.
+        r###"<p><sup><a href="#user-content-fn-*emphasis*" id="user-content-fnref-*emphasis*" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup></p>
+<p><sup><a href="#user-content-fn-**strong**" id="user-content-fnref-**strong**" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup></p>
+<p><sup><a href="#user-content-fn-%60code%60" id="user-content-fnref-%60code%60" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup></p>
+<p><sup><a href="#user-content-fn-www.example.com" id="user-content-fnref-www.example.com" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<p><sup><a href="#user-content-fn-https://example.com" id="user-content-fnref-https://example.com" data-footnote-ref="" aria-describedby="footnote-label">5</a></sup></p>
+<p><sup><a href="#user-content-fn-://example.com" id="user-content-fnref-://example.com" data-footnote-ref="" aria-describedby="footnote-label">6</a></sup></p>
+<p>[^<a href="#">link</a>]</p>
+<p>[^<img src="#" alt="image" />]</p>
+<p>[^<a href="#">link</a>]: a</p>
+<p>[^<img src="#" alt="image" />]: a</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-*emphasis*">
+<p>a <a href="#user-content-fnref-*emphasis*" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-**strong**">
+<p>a <a href="#user-content-fnref-**strong**" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-%60code%60">
+<p>a <a href="#user-content-fnref-%60code%60" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-www.example.com">
+<p>a <a href="#user-content-fnref-www.example.com" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-https://example.com">
+<p>a <a href="#user-content-fnref-https://example.com" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-://example.com">
+<p>a <a href="#user-content-fnref-://example.com" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match construct identifiers like GitHub (except for its bugs)"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Call[^1][^2][^3][^4]
+
+> [^1]: Defined in a block quote.
+>
+> More.
+[^2]: Directly after a block quote.
+
+* [^3]: Defined in a list item.
+
+  More.
+[^4]: Directly after a list item.
+"###,
+            &gfm
+        ),
+        r###"<p>Call<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<blockquote>
+<p>More.</p>
+</blockquote>
+<ul>
+<li>
+<p>More.</p>
+</li>
+</ul>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Defined in a block quote. <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>Directly after a block quote. <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>Defined in a list item. <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>Directly after a list item. <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match containers like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^1][^2][^3][^4]
+
+[^1]: Paragraph
+…continuation
+
+# Heading
+
+[^2]: Paragraph
+…continuation
+
+    “code”, which is paragraphs…
+
+    …because of the indent!
+
+[^3]: Paragraph
+…continuation
+
+> block quote
+
+[^4]: Paragraph
+…continuation
+
+- list
+"###,
+            &gfm
+        ),
+        r###"<p><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<h1>Heading</h1>
+<blockquote>
+<p>block quote</p>
+</blockquote>
+<ul>
+<li>list</li>
+</ul>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph
+…continuation</p>
+<p>“code”, which is paragraphs…</p>
+<p>…because of the indent! <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match continuation like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Call[^1][^2][^3][^4][^5].
+
+[^1]:
+    ---
+
+[^2]:
+    Paragraph.
+
+[^3]:
+Lazy?
+
+[^4]:
+
+    Another blank.
+
+[^5]:
+
+Lazy!
+"###,
+            &gfm
+        ),
+        r###"<p>Call<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup><sup><a href="#user-content-fn-5" id="user-content-fnref-5" data-footnote-ref="" aria-describedby="footnote-label">5</a></sup>.</p>
+<p>Lazy?</p>
+<p>Lazy!</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<hr />
+<a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph. <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-4">
+<p>Another blank. <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-5">
+<a href="#user-content-fnref-5" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+</ol>
+</section>
+"###,
+        "should match definitions initial blank like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Note![^0][^1][^2][^3][^4][^5][^6][^7][^8][^9][^10]
+
+[^0]: alpha
+
+[^1]: bravo
+
+[^2]: charlie
+    indented delta
+
+[^3]:    echo
+
+[^4]:     foxtrot
+
+[^5]:> golf
+
+[^6]:    > hotel
+
+[^7]:     > india
+
+[^8]: # juliett
+
+[^9]: ---
+
+[^10]:- - - kilo
+"###,
+            &gfm
+        ),
+        r###"<p>Note!<sup><a href="#user-content-fn-0" id="user-content-fnref-0" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">5</a></sup><sup><a href="#user-content-fn-5" id="user-content-fnref-5" data-footnote-ref="" aria-describedby="footnote-label">6</a></sup><sup><a href="#user-content-fn-6" id="user-content-fnref-6" data-footnote-ref="" aria-describedby="footnote-label">7</a></sup><sup><a href="#user-content-fn-7" id="user-content-fnref-7" data-footnote-ref="" aria-describedby="footnote-label">8</a></sup><sup><a href="#user-content-fn-8" id="user-content-fnref-8" data-footnote-ref="" aria-describedby="footnote-label">9</a></sup><sup><a href="#user-content-fn-9" id="user-content-fnref-9" data-footnote-ref="" aria-describedby="footnote-label">10</a></sup><sup><a href="#user-content-fn-10" id="user-content-fnref-10" data-footnote-ref="" aria-describedby="footnote-label">11</a></sup></p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-0">
+<p>alpha <a href="#user-content-fnref-0" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-1">
+<p>bravo <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>charlie
+indented delta <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>echo <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>foxtrot <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-5">
+<blockquote>
+<p>golf</p>
+</blockquote>
+<a href="#user-content-fnref-5" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-6">
+<blockquote>
+<p>hotel</p>
+</blockquote>
+<a href="#user-content-fnref-6" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-7">
+<blockquote>
+<p>india</p>
+</blockquote>
+<a href="#user-content-fnref-7" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-8">
+<h1>juliett</h1>
+<a href="#user-content-fnref-8" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-9">
+<hr />
+<a href="#user-content-fnref-9" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-10">
+<ul>
+<li>
+<ul>
+<li>
+<ul>
+<li>kilo</li>
+</ul>
+</li>
+</ul>
+</li>
+</ul>
+<a href="#user-content-fnref-10" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+</ol>
+</section>
+"###,
+        "should match definitions like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Call[^1][^1]
+
+[^1]: Recursion[^1][^1]
+"###,
+            &gfm
+        ),
+        r###"<p>Call<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-1" id="user-content-fnref-1-2" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup></p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Recursion<sup><a href="#user-content-fn-1" id="user-content-fnref-1-3" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-1" id="user-content-fnref-1-4" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup> <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a> <a href="#user-content-fnref-1-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩<sup>2</sup></a> <a href="#user-content-fnref-1-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩<sup>3</sup></a> <a href="#user-content-fnref-1-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩<sup>4</sup></a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match duplicate calls and recursion like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Call[^1]
+
+[^1]: a
+
+[^1]: b
+"###,
+            &gfm
+        ),
+        r###"<p>Call<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup></p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>a <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match duplicate definitions like GitHub"
+    );
+
+    // Note:
+    // * GH “supports” footnotes inside links.
+    //   This breaks an HTML parser, as it is not allowed.
+    //   See: <https://github.com/github/cmark-gfm/issues/275>
+    //   CommonMark has mechanisms in place to prevent links in links.
+    //   These mechanisms are in place here too.
+    assert_eq!(
+        micromark_with_options(
+            r###"*emphasis[^1]*
+
+**strong[^2]**
+
+`code[^3]`
+
+![image[^4]](#)
+
+[link[^5]](#)
+
+[^1]: a
+
+[^2]: b
+
+[^3]: c
+
+[^4]: d
+
+[^5]: e
+"###,
+            &gfm
+        ),
+        r###"<p><em>emphasis<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup></em></p>
+<p><strong>strong<sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup></strong></p>
+<p><code>code[^3]</code></p>
+<p><img src="#" alt="image" /></p>
+<p>[link<sup><a href="#user-content-fn-5" id="user-content-fnref-5" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup>](#)</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>a <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>b <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>d <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-5">
+<p>e <a href="#user-content-fnref-5" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match footnotes in constructs like GitHub (without the bugs)"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"What are these![^1], ![^2][], and ![this][^3].
+
+[^1]: a
+
+[^2]: b
+
+[^3]: c
+"###,
+            &gfm
+        ),
+        r###"<p>What are these!<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup>, !<sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup>[], and ![this]<sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup>.</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>a <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>b <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>c <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match images/footnotes like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^0][^1][^2][^3][^4][^5]
+
+[^0]: Paragraph
+…continuation
+[^1]: Another
+[^2]: Paragraph
+…continuation
+# Heading
+[^3]: Paragraph
+…continuation
+    “code”, which is paragraphs…
+
+    …because of the indent!
+[^4]: Paragraph
+…continuation
+> block quote
+[^5]: Paragraph
+…continuation
+*   list
+"###,
+            &gfm
+        ),
+        r###"<p><sup><a href="#user-content-fn-0" id="user-content-fnref-0" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">5</a></sup><sup><a href="#user-content-fn-5" id="user-content-fnref-5" data-footnote-ref="" aria-describedby="footnote-label">6</a></sup></p>
+<h1>Heading</h1>
+<blockquote>
+<p>block quote</p>
+</blockquote>
+<ul>
+<li>list</li>
+</ul>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-0">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-0" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-1">
+<p>Another <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>Paragraph
+…continuation
+“code”, which is paragraphs…</p>
+<p>…because of the indent! <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-5">
+<p>Paragraph
+…continuation <a href="#user-content-fnref-5" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match interrupt like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"What are these[^1], [^2][], and [this][^3].
+
+[^1]: a
+
+[^2]: b
+
+[^3]: c
+"###,
+            &gfm
+        ),
+        r###"<p>What are these<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup>, <sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup>[], and [this]<sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup>.</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>a <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>b <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>c <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match links/footnotes like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^1][^2][^3][^4]
+
+[^1]: Paragraph
+
+
+# Heading
+
+
+[^2]: Paragraph
+
+
+    “code”, which is paragraphs…
+
+
+    …because of the indent!
+
+
+[^3]: Paragraph
+
+
+> block quote
+
+
+[^4]: Paragraph
+
+
+- list
+"###,
+            &gfm
+        ),
+        r###"<p><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<h1>Heading</h1>
+<blockquote>
+<p>block quote</p>
+</blockquote>
+<ul>
+<li>list</li>
+</ul>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Paragraph <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph</p>
+<p>“code”, which is paragraphs…</p>
+<p>…because of the indent! <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>Paragraph <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match many blank lines/no indent like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^1][^2][^3][^4]
+
+[^1]: Paragraph
+
+
+    # Heading
+
+
+[^2]: Paragraph
+
+
+        code
+
+
+        more code
+
+
+[^3]: Paragraph
+
+
+    > block quote
+
+
+[^4]: Paragraph
+
+
+    - list
+"###,
+            &gfm
+        ),
+        r###"<p><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Paragraph</p>
+<h1>Heading</h1>
+<a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph</p>
+<pre><code>code
+
+
+more code
+</code></pre>
+<a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-3">
+<p>Paragraph</p>
+<blockquote>
+<p>block quote</p>
+</blockquote>
+<a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph</p>
+<ul>
+<li>list</li>
+</ul>
+<a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+</ol>
+</section>
+"###,
+        "should match many blank lines like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Note![^1][^2][^3][^4]
+
+- [^1]: Paragraph
+
+> [^2]: Paragraph
+
+[^3]: [^4]: Paragraph
+"###,
+            &gfm
+        ),
+        r###"<p>Note!<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<ul>
+<li></li>
+</ul>
+<blockquote>
+</blockquote>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Paragraph <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match nest like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^1][^2][^3][^4]
+
+[^1]: Paragraph
+
+# Heading
+
+[^2]: Paragraph
+
+    “code”, which is paragraphs…
+
+    …because of the indent!
+
+[^3]: Paragraph
+
+> block quote
+
+[^4]: Paragraph
+
+- list
+"###,
+            &gfm
+        ),
+        r###"<p><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<h1>Heading</h1>
+<blockquote>
+<p>block quote</p>
+</blockquote>
+<ul>
+<li>list</li>
+</ul>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Paragraph <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph</p>
+<p>“code”, which is paragraphs…</p>
+<p>…because of the indent! <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>Paragraph <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match normal blank lines/no indent like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"[^1][^2][^3][^4]
+
+[^1]: Paragraph
+
+    # Heading
+
+[^2]: Paragraph
+
+        code
+
+        more code
+
+[^3]: Paragraph
+
+    > block quote
+
+[^4]: Paragraph
+
+    - list
+"###,
+            &gfm
+        ),
+        r###"<p><sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup></p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Paragraph</p>
+<h1>Heading</h1>
+<a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-2">
+<p>Paragraph</p>
+<pre><code>code
+
+more code
+</code></pre>
+<a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-3">
+<p>Paragraph</p>
+<blockquote>
+<p>block quote</p>
+</blockquote>
+<a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-4">
+<p>Paragraph</p>
+<ul>
+<li>list</li>
+</ul>
+<a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+</ol>
+</section>
+"###,
+        "should match normal blank lines like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Here is a footnote reference,[^1] and another.[^longnote]
+
+[^1]: Here is the footnote.
+
+[^longnote]: Here’s one with multiple blocks.
+
+    Subsequent paragraphs are indented to show that they
+belong to the previous footnote.
+
+        { some.code }
+
+    The whole paragraph can be indented, or just the first
+    line.  In this way, multi-paragraph footnotes work like
+    multi-paragraph list items.
+
+This paragraph won’t be part of the note, because it
+isn’t indented.
+"###,
+            &gfm
+        ),
+        r###"<p>Here is a footnote reference,<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup> and another.<sup><a href="#user-content-fn-longnote" id="user-content-fnref-longnote" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup></p>
+<p>This paragraph won’t be part of the note, because it
+isn’t indented.</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>Here is the footnote. <a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-longnote">
+<p>Here’s one with multiple blocks.</p>
+<p>Subsequent paragraphs are indented to show that they
+belong to the previous footnote.</p>
+<pre><code>{ some.code }
+</code></pre>
+<p>The whole paragraph can be indented, or just the first
+line.  In this way, multi-paragraph footnotes work like
+multi-paragraph list items. <a href="#user-content-fnref-longnote" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match pandoc like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Call[^1][^2][^3][^4][^5][^6][^7][^8][^9][^10][^11][^12].
+
+     [^1]: 5
+
+    [^2]: 4
+
+   [^3]: 3
+
+  [^4]: 2
+
+ [^5]: 1
+
+[^6]: 0
+
+***
+
+   [^7]: 3
+
+     5
+
+   [^8]: 3
+
+    4
+
+   [^9]: 3
+
+   3
+
+  [^10]: 2
+
+     5
+
+  [^11]: 2
+
+    4
+
+  [^12]: 2
+
+   3
+"###,
+            &gfm
+        ),
+        r###"<p>Call[^1][^2]<sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-5" id="user-content-fnref-5" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-6" id="user-content-fnref-6" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup><sup><a href="#user-content-fn-7" id="user-content-fnref-7" data-footnote-ref="" aria-describedby="footnote-label">5</a></sup><sup><a href="#user-content-fn-8" id="user-content-fnref-8" data-footnote-ref="" aria-describedby="footnote-label">6</a></sup><sup><a href="#user-content-fn-9" id="user-content-fnref-9" data-footnote-ref="" aria-describedby="footnote-label">7</a></sup><sup><a href="#user-content-fn-10" id="user-content-fnref-10" data-footnote-ref="" aria-describedby="footnote-label">8</a></sup><sup><a href="#user-content-fn-11" id="user-content-fnref-11" data-footnote-ref="" aria-describedby="footnote-label">9</a></sup><sup><a href="#user-content-fn-12" id="user-content-fnref-12" data-footnote-ref="" aria-describedby="footnote-label">10</a></sup>.</p>
+<pre><code> [^1]: 5
+
+[^2]: 4
+</code></pre>
+<hr />
+<p>3</p>
+<p>3</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-3">
+<p>3 <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>2 <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-5">
+<p>1 <a href="#user-content-fnref-5" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-6">
+<p>0 <a href="#user-content-fnref-6" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-7">
+<p>3</p>
+<p>5 <a href="#user-content-fnref-7" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-8">
+<p>3</p>
+<p>4 <a href="#user-content-fnref-8" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-9">
+<p>3 <a href="#user-content-fnref-9" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-10">
+<p>2</p>
+<p>5 <a href="#user-content-fnref-10" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-11">
+<p>2</p>
+<p>4 <a href="#user-content-fnref-11" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-12">
+<p>2 <a href="#user-content-fnref-12" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match prefix before like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Call[^1][^2][^3][^4][^5][^6][^7][^8][^9].
+
+[^1]: a
+
+        8
+
+[^2]: a
+
+       7
+
+[^3]: a
+
+      6
+
+[^4]: a
+
+     5
+
+[^5]: a
+
+    4
+
+[^6]: a
+
+   3
+
+[^7]: a
+
+  2
+
+[^8]: a
+
+ 1
+
+[^9]: a
+
+0
+"###,
+            &gfm
+        ),
+        r###"<p>Call<sup><a href="#user-content-fn-1" id="user-content-fnref-1" data-footnote-ref="" aria-describedby="footnote-label">1</a></sup><sup><a href="#user-content-fn-2" id="user-content-fnref-2" data-footnote-ref="" aria-describedby="footnote-label">2</a></sup><sup><a href="#user-content-fn-3" id="user-content-fnref-3" data-footnote-ref="" aria-describedby="footnote-label">3</a></sup><sup><a href="#user-content-fn-4" id="user-content-fnref-4" data-footnote-ref="" aria-describedby="footnote-label">4</a></sup><sup><a href="#user-content-fn-5" id="user-content-fnref-5" data-footnote-ref="" aria-describedby="footnote-label">5</a></sup><sup><a href="#user-content-fn-6" id="user-content-fnref-6" data-footnote-ref="" aria-describedby="footnote-label">6</a></sup><sup><a href="#user-content-fn-7" id="user-content-fnref-7" data-footnote-ref="" aria-describedby="footnote-label">7</a></sup><sup><a href="#user-content-fn-8" id="user-content-fnref-8" data-footnote-ref="" aria-describedby="footnote-label">8</a></sup><sup><a href="#user-content-fn-9" id="user-content-fnref-9" data-footnote-ref="" aria-describedby="footnote-label">9</a></sup>.</p>
+<p>3</p>
+<p>2</p>
+<p>1</p>
+<p>0</p>
+<section data-footnotes="" class="footnotes"><h2 id="footnote-label" class="sr-only">Footnotes</h2>
+<ol>
+<li id="user-content-fn-1">
+<p>a</p>
+<pre><code>8
+</code></pre>
+<a href="#user-content-fnref-1" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a>
+</li>
+<li id="user-content-fn-2">
+<p>a</p>
+<p>7 <a href="#user-content-fnref-2" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-3">
+<p>a</p>
+<p>6 <a href="#user-content-fnref-3" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-4">
+<p>a</p>
+<p>5 <a href="#user-content-fnref-4" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-5">
+<p>a</p>
+<p>4 <a href="#user-content-fnref-5" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-6">
+<p>a <a href="#user-content-fnref-6" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-7">
+<p>a <a href="#user-content-fnref-7" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-8">
+<p>a <a href="#user-content-fnref-8" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+<li id="user-content-fn-9">
+<p>a <a href="#user-content-fnref-9" data-footnote-backref="" class="data-footnote-backref" aria-label="Back to content">↩</a></p>
+</li>
+</ol>
+</section>
+"###,
+        "should match prefix like GitHub"
+    );
+
+    assert_eq!(
+        micromark_with_options(
+            r###"Here is a short reference,[1], a collapsed one,[2][], and a full [one][3].
+
+[1]: a
+
+[2]: b
+
+[3]: c
+"###,
+            &gfm
+        ),
+        r###"<p>Here is a short reference,<a href="a">1</a>, a collapsed one,<a href="b">2</a>, and a full <a href="c">one</a>.</p>
+"###,
+        "should match references and definitions like GitHub"
+    );
+}