feat: add load_from_file jinja function (prefix-dev#468)

Cargo.toml

@@ -96,10 +96,11 @@ zip = { version = "0.6.6", default-features = false, features = [
     "deflate",
 ] }
 bzip2 = "0.4.4"
+base64 = "0.21.6"
 flate2 = "1.0.28"
 xz2 = "0.1.7"
 zstd = "0.13.0"
-base64 = "0.21.6"
+toml = "0.8.8"
 
 [dev-dependencies]
 insta = { version = "1.34.0", features = ["yaml"] }

src/packaging.rs

@@ -133,7 +133,7 @@ fn contains_prefix_text(file_path: &Path, prefix: &Path) -> Result<bool, Packagi
 }
 
 #[allow(dead_code)]
-fn to_forward_slash_lossy(path: &Path) -> std::borrow::Cow<'_, str> {
+pub(crate) fn to_forward_slash_lossy(path: &Path) -> std::borrow::Cow<'_, str> {
     #[cfg(target_os = "windows")]
     {
         let mut buf = String::new();

src/recipe/jinja.rs

@@ -178,6 +178,7 @@ fn set_jinja(config: &SelectorConfig) -> minijinja::Environment<'static> {
         target_platform,
         build_platform,
         variant,
+        experimental,
         ..
     } = config.clone();
     env.add_function("cdt", move |package_name: String| {
@@ -241,6 +242,37 @@ fn set_jinja(config: &SelectorConfig) -> minijinja::Environment<'static> {
         format!("{}{}", major, minor)
     });
 
+    env.add_function("load_from_file", move |path: String| {
+        if !experimental {
+            return Err(minijinja::Error::new(
+                minijinja::ErrorKind::InvalidOperation,
+                "Experimental feature: provide the `--experimental` flag to enable this feature",
+            ));
+        }
+        let src = std::fs::read_to_string(&path).map_err(|e| {
+            minijinja::Error::new(minijinja::ErrorKind::UndefinedError, e.to_string())
+        })?;
+        // tracing::info!("loading from path: {path}");
+        let filename = path
+            .split('/')
+            .last()
+            .expect("unreachable: split will always atleast return empty string");
+        // tracing::info!("loading filename: {filename}");
+        let value: minijinja::Value = match filename.split_once('.') {
+            Some((_, "yaml")) | Some((_, "yml")) => serde_yaml::from_str(&src).map_err(|e| {
+                minijinja::Error::new(minijinja::ErrorKind::CannotDeserialize, e.to_string())
+            })?,
+            Some((_, "json")) => serde_json::from_str(&src).map_err(|e| {
+                minijinja::Error::new(minijinja::ErrorKind::CannotDeserialize, e.to_string())
+            })?,
+            Some((_, "toml")) => toml::from_str(&src).map_err(|e| {
+                minijinja::Error::new(minijinja::ErrorKind::CannotDeserialize, e.to_string())
+            })?,
+            _ => Value::from(src),
+        };
+        Ok(value)
+    });
+
     env
 }
 
@@ -557,6 +589,8 @@ mod tests {
 
     use rattler_conda_types::Platform;
 
+    use crate::packaging::to_forward_slash_lossy;
+
     use super::*;
 
     fn with_temp_dir(key: &'static str, f: impl Fn(&std::path::Path)) {
@@ -633,6 +667,44 @@ mod tests {
         });
     }
 
+    #[test]
+    #[rustfmt::skip]
+    fn eval_load_from_file() {
+        let options = SelectorConfig {
+            target_platform: Platform::Linux64,
+            build_platform: Platform::Linux64,
+            experimental: true,
+            ..Default::default()
+        };
+
+        let jinja = Jinja::new(options);
+
+        let temp_dir = tempfile::tempdir().unwrap();
+        let path = temp_dir.path().join("test.json");
+        let path_str = to_forward_slash_lossy(&path);
+        std::fs::write(&path, "{ \"hello\": \"world\" }").unwrap();
+        assert_eq!(
+            jinja.eval(&format!("load_from_file('{}')['hello']", path_str)).expect("test 1").as_str(),
+            Some("world"),
+        ); 
+
+        let path = temp_dir.path().join("test.yaml");
+        std::fs::write(&path, "hello: world").unwrap();
+        let path_str = to_forward_slash_lossy(&path);
+        assert_eq!(
+            jinja.eval(&format!("load_from_file('{}')['hello']", path_str)).expect("test 2").as_str(),
+            Some("world"),
+        ); 
+
+        let path = temp_dir.path().join("test.toml");
+        let path_str = to_forward_slash_lossy(&path);
+        std::fs::write(&path, "hello = 'world'").unwrap();
+        assert_eq!(
+            jinja.eval(&format!("load_from_file('{}')['hello']", path_str)).expect("test 2").as_str(),
+            Some("world"),
+        ); 
+    }
+
     #[test]
     #[rustfmt::skip]
     fn eval() {