Change resolve_ast return type.

src/engine_api.rs

@@ -936,11 +936,15 @@ impl Engine {
             while let Some(path) = imports.iter().next() {
                 let path = path.clone();
 
-                if let Some(module_ast) =
-                    self.module_resolver
-                        .resolve_ast(self, &path, Position::NONE)?
+                match self
+                    .module_resolver
+                    .resolve_ast(self, &path, Position::NONE)
                 {
-                    collect_imports(&module_ast, &mut resolver, &mut imports);
+                    Some(Ok(module_ast)) => {
+                        collect_imports(&module_ast, &mut resolver, &mut imports)
+                    }
+                    Some(err @ Err(_)) => return err,
+                    None => (),
                 }
 
                 let module = shared_take_or_clone(self.module_resolver.resolve(

src/module/mod.rs

@@ -168,27 +168,48 @@ impl fmt::Debug for Module {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "Module({}\n    modules: {}\n    vars: {}\n    functions: {}\n)",
+            "Module({}\n{}{}{})",
             if let Some(ref id) = self.id {
-                format!("id: {:?}", id)
+                format!("id: {:?},", id)
             } else {
                 "".to_string()
             },
-            self.modules
-                .keys()
-                .map(|m| m.as_str())
-                .collect::<Vec<_>>()
-                .join(", "),
-            self.variables
-                .iter()
-                .map(|(k, v)| format!("{}={:?}", k, v))
-                .collect::<Vec<_>>()
-                .join(", "),
-            self.functions
-                .values()
-                .map(|FuncInfo { func, .. }| func.to_string())
-                .collect::<Vec<_>>()
-                .join(", "),
+            if !self.modules.is_empty() {
+                format!(
+                    "    modules: {}\n",
+                    self.modules
+                        .keys()
+                        .map(|m| m.as_str())
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )
+            } else {
+                "".to_string()
+            },
+            if !self.variables.is_empty() {
+                format!(
+                    "    vars: {}\n",
+                    self.variables
+                        .iter()
+                        .map(|(k, v)| format!("{}={:?}", k, v))
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )
+            } else {
+                "".to_string()
+            },
+            if !self.functions.is_empty() {
+                format!(
+                    "    functions: {}\n",
+                    self.functions
+                        .values()
+                        .map(|FuncInfo { func, .. }| func.to_string())
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )
+            } else {
+                "".to_string()
+            }
         )
     }
 }

src/module/resolvers/file.rs

@@ -233,22 +233,24 @@ impl ModuleResolver for FileModuleResolver {
         engine: &Engine,
         path: &str,
         pos: Position,
-    ) -> Result<Option<crate::AST>, Box<EvalAltResult>> {
+    ) -> Option<Result<crate::AST, Box<EvalAltResult>>> {
         // Construct the script file path
         let mut file_path = self.base_path.clone();
         file_path.push(path);
         file_path.set_extension(&self.extension); // Force extension
 
         // Load the script file and compile it
-        let mut ast = engine.compile_file(file_path).map_err(|err| match *err {
+        match engine.compile_file(file_path).map_err(|err| match *err {
             EvalAltResult::ErrorSystem(_, err) if err.is::<IoError>() => {
                 Box::new(EvalAltResult::ErrorModuleNotFound(path.to_string(), pos))
             }
             _ => Box::new(EvalAltResult::ErrorInModule(path.to_string(), err, pos)),
-        })?;
-
-        ast.set_source(path);
-
-        Ok(Some(ast))
+        }) {
+            Ok(mut ast) => {
+                ast.set_source(path);
+                Some(Ok(ast))
+            }
+            err @ Err(_) => Some(err),
+        }
     }
 }

src/module/resolvers/mod.rs

@@ -44,7 +44,7 @@ pub trait ModuleResolver: SendSync {
         engine: &Engine,
         path: &str,
         pos: Position,
-    ) -> Result<Option<AST>, Box<EvalAltResult>> {
-        Ok(None)
+    ) -> Option<Result<AST, Box<EvalAltResult>>> {
+        None
     }
 }