Move tightly coupled code from derive to shared crate

1 files changed, 111 insertions, 2 deletions

diff --git a/askama_shared/src/lib.rs b/askama_shared/src/lib.rs
index b5bc9af..60a263f 100644
--- a/askama_shared/src/lib.rs
+++ b/askama_shared/src/lib.rs
@@ -14,13 +14,90 @@ pub use escaping::MarkupDisplay;
 pub use errors::{Error, Result};
 pub mod filters;
 pub mod path;
-pub use parser::parse;
-pub use generator::generate;
 
 mod escaping;
 mod generator;
 mod parser;
 
+use std::borrow::Cow;
+use std::path::PathBuf;
+
+
+/// Takes a `syn::DeriveInput` and generates source code for it
+///
+/// Reads the metadata from the `template()` attribute to get the template
+/// metadata, then fetches the source from the filesystem. The source is
+/// parsed, and the parse tree is fed to the code generator. Will print
+/// the parse tree and/or generated source according to the `print` key's
+/// value as passed to the `template()` attribute.
+pub fn build_template(ast: &syn::DeriveInput) -> String {
+    let meta = get_template_meta(ast);
+    let (path, src) = match meta.source {
+        Source::Source(s) => (PathBuf::new(), Cow::Borrowed(s)),
+        Source::Path(s) => {
+            let path = path::find_template_from_path(&s, None);
+            let src = path::get_template_source(&path);
+            (path, Cow::Owned(src))
+        },
+    };
+    let nodes = parser::parse(src.as_ref());
+    if meta.print == Print::Ast || meta.print == Print::All {
+        println!("{:?}", nodes);
+    }
+    let code = generator::generate(ast, &path, nodes);
+    if meta.print == Print::Code || meta.print == Print::All {
+        println!("{}", code);
+    }
+    code
+}
+
+// Returns a `TemplateMeta` based on the `template()` attribute data found
+// in the parsed struct or enum. Will panic if it does not find the required
+// template path, or if the `print` key has an unexpected value.
+fn get_template_meta<'a>(ast: &'a syn::DeriveInput) -> TemplateMeta<'a> {
+    let attr = ast.attrs.iter().find(|a| a.name() == "template");
+    if attr.is_none() {
+        let msg = format!("'template' attribute not found on struct '{}'",
+                          ast.ident.as_ref());
+        panic!(msg);
+    }
+
+    let attr = attr.unwrap();
+    let mut source = None;
+    let mut print = Print::None;
+    if let syn::MetaItem::List(_, ref inner) = attr.value {
+        for nm_item in inner {
+            if let syn::NestedMetaItem::MetaItem(ref item) = *nm_item {
+                if let syn::MetaItem::NameValue(ref key, ref val) = *item {
+                    match key.as_ref() {
+                        "path" => if let syn::Lit::Str(ref s, _) = *val {
+                            source = Some(Source::Path(s.as_ref()));
+                        } else {
+                            panic!("template path must be string literal");
+                        },
+                        "source" => if let syn::Lit::Str(ref s, _) = *val {
+                            source = Some(Source::Source(s.as_ref()));
+                        } else {
+                            panic!("template source must be string literal");
+                        },
+                        "print" => if let syn::Lit::Str(ref s, _) = *val {
+                            print = s.into();
+                        } else {
+                            panic!("print value must be string literal");
+                        },
+                        _ => { panic!("unsupported annotation key found") }
+                    }
+                }
+            }
+        }
+    }
+
+    match source {
+        Some(s) => TemplateMeta { source: s, print },
+        None => panic!("template path or source not found in struct attributes"),
+    }
+}
+
 mod errors {
     error_chain! {
         foreign_links {
@@ -29,3 +106,35 @@ mod errors {
         }
     }
 }
+
+// Holds metadata for the template, based on the `template()` attribute.
+struct TemplateMeta<'a> {
+    source: Source<'a>,
+    print: Print,
+}
+
+enum Source<'a> {
+    Path(&'a str),
+    Source(&'a str),
+}
+
+#[derive(PartialEq)]
+enum Print {
+    All,
+    Ast,
+    Code,
+    None,
+}
+
+impl<'a> From<&'a String> for Print {
+    fn from(s: &'a String) -> Print {
+        use Print::*;
+        match s.as_ref() {
+            "all" => All,
+            "ast" => Ast,
+            "code" => Code,
+            "none" => None,
+            v => panic!("invalid value for print option: {}", v),
+        }
+    }
+}