1 files changed, 69 insertions, 1 deletions
diff --git a/askama_shared/src/lib.rs b/askama_shared/src/lib.rs
index 2c2a88f..08b243d 100644
--- a/askama_shared/src/lib.rs
+++ b/askama_shared/src/lib.rs
@@ -9,7 +9,7 @@ extern crate toml;
 
 use std::env;
 use std::fs;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 mod error;
 mod escaping;
@@ -43,6 +43,27 @@ impl Config {
 
         Config { dirs }
     }
+
+    pub fn find_template(&self, path: &str, start_at: Option<&Path>) -> PathBuf {
+        if let Some(root) = start_at {
+            let relative = root.with_file_name(path);
+            if relative.exists() {
+                return relative.to_owned();
+            }
+        }
+
+        for dir in &self.dirs {
+            let rooted = dir.join(path);
+            if rooted.exists() {
+                return rooted;
+            }
+        }
+
+        panic!(
+            "template {:?} not found in directories {:?}",
+            path, self.dirs
+        )
+    }
 }
 
 #[derive(Deserialize)]
@@ -51,3 +72,50 @@ struct RawConfig {
 }
 
 static CONFIG_FILE_NAME: &str = "askama.toml";
+
+#[cfg(test)]
+mod tests {
+    use super::Config;
+    use std::env;
+    use std::path::{Path, PathBuf};
+
+    fn assert_eq_rooted(actual: &Path, expected: &str) {
+        let mut root = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
+        root.push("templates");
+        let mut inner = PathBuf::new();
+        inner.push(expected);
+        assert_eq!(actual.strip_prefix(root).unwrap(), inner);
+    }
+
+    #[test]
+    fn find_absolute() {
+        let config = Config::new();
+        let root = config.find_template("a.html", None);
+        let path = config.find_template("sub/b.html", Some(&root));
+        assert_eq_rooted(&path, "sub/b.html");
+    }
+
+    #[test]
+    #[should_panic]
+    fn find_relative_nonexistent() {
+        let config = Config::new();
+        let root = config.find_template("a.html", None);
+        config.find_template("b.html", Some(&root));
+    }
+
+    #[test]
+    fn find_relative() {
+        let config = Config::new();
+        let root = config.find_template("sub/b.html", None);
+        let path = config.find_template("c.html", Some(&root));
+        assert_eq_rooted(&path, "sub/c.html");
+    }
+
+    #[test]
+    fn find_relative_sub() {
+        let config = Config::new();
+        let root = config.find_template("sub/b.html", None);
+        let path = config.find_template("sub1/d.html", Some(&root));
+        assert_eq_rooted(&path, "sub/sub1/d.html");
+    }
+}