rearchitect PathSearcher as PolySearcher

to genericize conversion of paths to lua source code
- which facilitates module reloading for e.g.
  - fennel
  - teal
  - typescripttolua

src/searcher.rs

@@ -3,7 +3,7 @@ use rlua::{Context, MetaMethod, RegistryKey, Table, UserData, UserDataMethods, V
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::Read;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use crate::types::Result;
 use crate::utils;
@@ -72,26 +72,40 @@ impl UserData for StaticSearcher {
     }
 }
 
-/// Like `Searcher`, but with `modules` values given as paths to files containing Lua
-/// source code to facilitate module reloading.
-struct PathSearcher<P>
+/// Like `Searcher`, but with `modules` values given as paths to files the content of
+/// which can be read as Lua source code.
+///
+/// Facilitates Lua module reloading, and module reloading of any other programming
+/// language whose source code can be compiled to Lua.
+struct PolySearcher<P>
 where
     P: 'static + AsRef<Path> + Send,
 {
     modules: HashMap<String, P>,
     globals: RegistryKey,
+
+    /// Function to read file content as Lua source code.
+    convert: Box<dyn Fn(PathBuf) -> rlua::Result<String> + Send>,
 }
 
-impl<P> PathSearcher<P>
+impl<P> PolySearcher<P>
 where
     P: 'static + AsRef<Path> + Send,
 {
-    fn new(modules: HashMap<String, P>, globals: RegistryKey) -> Self {
-        Self { modules, globals }
+    fn new(
+        modules: HashMap<String, P>,
+        globals: RegistryKey,
+        convert: Box<dyn Fn(PathBuf) -> rlua::Result<String> + Send>,
+    ) -> Self {
+        Self {
+            modules,
+            globals,
+            convert,
+        }
     }
 }
 
-impl<P> UserData for PathSearcher<P>
+impl<P> UserData for PolySearcher<P>
 where
     P: 'static + AsRef<Path> + Send,
 {
@@ -108,11 +122,7 @@ where
                         path.to_path_buf()
                     };
 
-                    let mut content = String::new();
-                    let mut file = File::open(path)
-                        .map_err(|e| LuaError::RuntimeError(format!("io error: {:#?}", e)))?;
-                    file.read_to_string(&mut content)
-                        .map_err(|e| LuaError::RuntimeError(format!("io error: {:#?}", e)))?;
+                    let content = (this.convert)(path)?;
 
                     Ok(Value::Function(
                         lua_ctx
@@ -144,6 +154,16 @@ pub trait AddSearcher {
     fn add_path_searcher<P>(&self, modules: HashMap<String, P>) -> Result<()>
     where
         P: 'static + AsRef<Path> + Send;
+
+    /// Like `add_path_searcher`, but with user-provided closure for converting source
+    /// code to Lua.
+    fn add_poly_searcher<P>(
+        &self,
+        modules: HashMap<String, P>,
+        convert: Box<dyn Fn(PathBuf) -> rlua::Result<String> + Send>,
+    ) -> Result<()>
+    where
+        P: 'static + AsRef<Path> + Send;
 }
 
 impl<'a> AddSearcher for Context<'a> {
@@ -168,13 +188,32 @@ impl<'a> AddSearcher for Context<'a> {
     }
 
     fn add_path_searcher<P>(&self, modules: HashMap<String, P>) -> Result<()>
+    where
+        P: 'static + AsRef<Path> + Send,
+    {
+        let convert = Box::new(|path| {
+            let mut content = String::new();
+            let mut file = File::open(path)
+                .map_err(|e| LuaError::RuntimeError(format!("io error: {:#?}", e)))?;
+            file.read_to_string(&mut content)
+                .map_err(|e| LuaError::RuntimeError(format!("io error: {:#?}", e)))?;
+            Ok(content)
+        });
+        self.add_poly_searcher(modules, convert)
+    }
+
+    fn add_poly_searcher<P>(
+        &self,
+        modules: HashMap<String, P>,
+        convert: Box<dyn Fn(PathBuf) -> rlua::Result<String> + Send>,
+    ) -> Result<()>
     where
         P: 'static + AsRef<Path> + Send,
     {
         let globals = self.globals();
         let searchers: Table = globals.get::<_, Table>("package")?.get("searchers")?;
         let registry_key = self.create_registry_value(globals)?;
-        let searcher = PathSearcher::new(modules, registry_key);
+        let searcher = PolySearcher::new(modules, registry_key, convert);
         searchers
             .set(searchers.len()? + 1, searcher)
             .map_err(|e| e.into())