One shot file compilation

CHANGELOG.md

@@ -25,6 +25,8 @@
 
 #### :rocket: New Feature
 
+- Add `rescript compile-file` command for one-shot compilation of a single ReScript file to JavaScript, outputting to stdout. Supports `--module-format` flag to select output format when multiple package-specs are configured. https://github.com/rescript-lang/rescript/pull/8002
+
 #### :bug: Bug fix
 
 - Reanalyze: fix reactive/server stale results when cross-file references change without changing dead declarations (non-transitive mode). https://github.com/rescript-lang/rescript/pull/8173

compiler/bsc/rescript_compiler_main.ml

@@ -259,10 +259,23 @@ let command_line_flags : (string * Bsc_args.spec * string) array =
       string_call ignore,
       "*internal* Set jsx mode, this is no longer used and is a no-op." );
     ("-bs-jsx-preserve", set Js_config.jsx_preserve, "*internal* Preserve jsx");
+    ( "-bs-module-system",
+      string_call (fun s ->
+          Js_config.default_module_system :=
+            match Js_packages_info.module_system_of_string s with
+            | Some ms -> ms
+            | None ->
+              Bsc_args.bad_arg
+                ("Invalid module system: " ^ s
+               ^ ". Use: commonjs, esmodule, or es6-global")),
+      "*internal* Set module system: commonjs, esmodule, es6-global" );
+    ( "-bs-suffix",
+      string_call (fun s -> Js_config.default_suffix := s),
+      "*internal* Set import file suffix: .js, .mjs, .cjs" );
     ( "-bs-package-output",
       string_call Js_packages_state.update_npm_package_path,
-      "*internal* Set npm-output-path: [opt_module]:path, for example: \
-       'lib/cjs', 'amdjs:lib/amdjs', 'es6:lib/es6' " );
+      "*internal* Set output path (when combined with -bs-module-system and \
+       -bs-suffix)" );
     ( "-bs-ast",
       unit_call (fun _ ->
           Js_config.binary_ast := true;

compiler/common/js_config.ml

@@ -52,6 +52,8 @@ let jsx_version = ref None
 let jsx_module = ref React
 let jsx_preserve = ref false
 let js_stdout = ref true
+let default_module_system = ref Ext_module_system.Commonjs
+let default_suffix = ref Literals.suffix_js
 let all_module_aliases = ref false
 let no_stdlib = ref false
 let no_export = ref false

compiler/common/js_config.mli

@@ -84,6 +84,10 @@ val jsx_preserve : bool ref
 
 val js_stdout : bool ref
 
+val default_module_system : Ext_module_system.t ref
+
+val default_suffix : string ref
+
 val all_module_aliases : bool ref
 
 val no_stdlib : bool ref

compiler/core/js_name_of_module_id.ml

@@ -57,6 +57,7 @@ let get_runtime_module_path
   let current_info_query = 
     Js_packages_info.query_package_infos current_package_info
       module_system  in
+  (* Runtime package is pre-compiled and always uses .js suffix *)
   let js_file =  
     Ext_namespace.js_name_of_modulename dep_module_id.id.name 
       Upper Literals.suffix_js in 
@@ -177,8 +178,9 @@ let string_of_module_id
             end
         | Package_script, Package_script 
           -> 
+          (* Use configured suffix instead of hardcoded .js *)
           let js_file =  
-            Ext_namespace.js_name_of_modulename dep_module_id.id.name case Literals.suffix_js in 
+            Ext_namespace.js_name_of_modulename dep_module_id.id.name case !Js_config.default_suffix in 
           match Config_util.find_opt js_file with 
           | Some file -> 
             let basename = Filename.basename file in 

compiler/core/js_packages_info.ml

@@ -192,13 +192,21 @@ let add_npm_package_path (packages_info : t) (s : string) : t =
     in
     let m =
       match Ext_string.split ~keep_empty:true s ':' with
-      | [path] -> {module_system = Esmodule; path; suffix = Literals.suffix_js}
+      (* NEW: Just path - use configured module system and suffix *)
+      | [path] ->
+        {
+          module_system = !Js_config.default_module_system;
+          path;
+          suffix = !Js_config.default_suffix;
+        }
+      (* OLD: module_system:path - use configured suffix *)
       | [module_system; path] ->
         {
           module_system = handle_module_system module_system;
           path;
-          suffix = Literals.suffix_js;
+          suffix = !Js_config.default_suffix;
         }
+      (* OLD: Full format - all explicit *)
       | [module_system; path; suffix] ->
         {module_system = handle_module_system module_system; path; suffix}
       | _ -> Bsc_args.bad_arg ("invalid npm package path: " ^ s)

compiler/core/js_packages_info.mli

@@ -50,6 +50,9 @@ val is_empty : t -> bool
 
 val dump_packages_info : Format.formatter -> t -> unit
 
+val module_system_of_string : string -> module_system option
+(** Parse module system from string (commonjs, esmodule, es6, es6-global) *)
+
 val add_npm_package_path : t -> string -> t
 (** used by command line option 
     e.g [-bs-package-output commonjs:xx/path]