[js] Module import support

Author: RblSb

src-json/meta.json

@@ -550,6 +550,13 @@
 		"targets": ["TClass"],
 		"links": ["https://haxe.org/manual/target-javascript-require.html"]
 	},
+	{
+		"name": "JsImport",
+		"metadata": ":js.import",
+		"doc": "Generate ES module import statement for given extern. Produces import lines at the top of the generated JS output.",
+		"platforms": ["js"],
+		"targets": ["TClass"]
+	},
 	{
 		"name": "LuaRequire",
 		"metadata": ":luaRequire",

src/generators/genjs.ml

@@ -1677,6 +1677,43 @@ let generate js_gen com =
 
 	let ctx = alloc_ctx com es_version in
 	Gctx.map_source_header com.defines (fun s -> print ctx "// %s\n" s);
+
+	let import_statements = ref [] in
+	let () =
+		List.iter (fun mt -> match mt with
+			| TClassDecl c when (has_class_flag c CExtern) && Meta.has Meta.JsImport c.cl_meta && is_directly_used ctx.com c.cl_meta ->
+				let _, args, mp = Meta.get Meta.JsImport c.cl_meta in
+				let id = s_path ctx (get_generated_class_path c) in
+				(match args with
+				(* @:js.import(@star "module") - namespace import *)
+				| [EMeta ((Meta.Custom "star",[],_),(EConst(String(module_name,_)),_)),_] ->
+					import_statements := (Printf.sprintf "import * as %s from \"%s\";" id module_name) :: !import_statements
+				(* @:js.import(@default "module") - default import *)
+				| [EMeta ((Meta.Custom "default",[],_),(EConst(String(module_name,_)),_)),_] ->
+					import_statements := (Printf.sprintf "import %s from \"%s\";" id module_name) :: !import_statements
+				(* @:js.import("module") - named import using class name *)
+				| [(EConst(String(module_name,_)),_)] ->
+					import_statements := (Printf.sprintf "import { %s } from \"%s\";" id module_name) :: !import_statements
+				(* @:js.import("module", "exportName") - named import with alias *)
+				| [(EConst(String(module_name,_)),_); (EConst(String(export_name,_)),_)] ->
+					if export_name = id then
+						import_statements := (Printf.sprintf "import { %s } from \"%s\";" id module_name) :: !import_statements
+					else
+						import_statements := (Printf.sprintf "import { %s as %s } from \"%s\";" export_name id module_name) :: !import_statements
+				| exprs ->
+					abort "Unsupported @:js.import format. Use: @:js.import('module'), @:js.import('module', 'name'), @:js.import(@default 'module'), or @:js.import(@star 'module')" mp
+				)
+			| _ -> ()
+		) com.types;
+	in
+	(match !import_statements with
+		| [] -> ()
+		| lines ->
+			List.iter (fun line ->
+				print ctx "%s\n" line
+			) (List.rev lines)
+	);
+
 	if has_feature ctx "Class" || has_feature ctx "Type.getClassName" then add_feature ctx "js.Boot.isClass";
 	if has_feature ctx "Enum" || has_feature ctx "Type.getEnumName" then add_feature ctx "js.Boot.isEnum";
 

tests/misc/projects/Issue10615/Main.hx

@@ -0,0 +1,56 @@
+@:js.import(@star '../lib.js')
+extern class Lib {
+	@:native("default") static function default_():Bool;
+	static var str:String;
+	static function increment(i:Int):Int;
+}
+
+@:js.import(@star '../lib_default_fun.js')
+extern class DefaultFun {
+	@:native("default") static function default_():Bool;
+}
+
+@:js.import(@default '../lib_default_class.js')
+extern class DefaultClass {
+	static function def():Bool;
+}
+
+@:js.import('../multilib.js')
+extern class Foo {
+	static function name():String;
+}
+@:js.import('../multilib.js', 'Foo')
+extern class Foo2 {
+	static function name():String;
+}
+@:js.import('../multilib.js', 'Bar')
+extern class Bar2 {
+	static function name():String;
+}
+
+@:js.import(@default '../multilib.js')
+extern class DefaultClass2 {
+	function new();
+	function name():Bool;
+}
+
+class Main {
+	static function main() {
+		eq("str", Lib.str);
+		eq(2, Lib.increment(1));
+		eq("default function", Lib.default_());
+
+		eq("foo", Foo.name());
+		eq("foo", Foo2.name());
+		eq("bar", Bar2.name());
+		final def = new DefaultClass2();
+		eq("default class", def.name());
+
+		eq("default function", DefaultFun.default_());
+		eq("default static", DefaultClass.def());
+	}
+
+	static function eq(a:Any, b:Any):Void {
+		if (a != b) throw '$a is not $b';
+	}
+}

tests/misc/projects/Issue10615/compile.hxml

@@ -0,0 +1,5 @@
+--main Main
+-dce full
+-D analyzer-optimize
+--js bin/main.js
+--cmd node bin/main

tests/misc/projects/Issue10615/compile2.hxml

@@ -0,0 +1,6 @@
+--main Main
+-dce full
+-D analyzer-optimize
+--js bin/main.js
+--cmd node bin/main
+-D js-es=6

tests/misc/projects/Issue10615/lib.js

@@ -0,0 +1,8 @@
+export const str = "str";
+export function increment(x) {
+    return x + 1;
+}
+
+export default function def() {
+    return "default function";
+}

tests/misc/projects/Issue10615/lib_default_class.js

@@ -0,0 +1,6 @@
+export default class Lib {
+    static def() {
+        return "default static";
+    }
+}
+

tests/misc/projects/Issue10615/lib_default_fun.js

@@ -0,0 +1,3 @@
+export default function def() {
+    return "default function";
+}

tests/misc/projects/Issue10615/multilib.js

@@ -0,0 +1,17 @@
+export class Foo {
+    static name() {
+        return "foo";
+    }
+}
+
+export class Bar {
+    static name() {
+        return "bar";
+    }
+}
+
+export default class DefClass {
+    name() {
+        return "default class";
+    }
+}