Import the default export for @scope starting with "default"

changes/scope-default-import.polish.md

@@ -0,0 +1 @@
+- Import the default export, instead of the module namespace, for `@module` externals whose `@scope` starts with `"default"`.

compiler/core/lam_compile_external_call.ml

@@ -223,8 +223,9 @@ let translate_scoped_module_val
       E.external_var_field ?import_attributes ~external_name:bundle ~field:fn
         ~default id
     | x :: rest ->
-      (* TODO: what happens when scope contains "default" ?*)
-      let default = false in
+      (* A leading "default" scope is the module's default export: import
+         it as such, like [external x: t = "default"] *)
+      let default = x = "default" in
       let id =
         Lam_compile_env.add_js_module ?import_attributes module_bind_name bundle
           default ~dynamic_import:false

tests/commonjs_tests/src/scope_default_import.res

@@ -0,0 +1,11 @@
+// A leading "default" scope imports the module's default export
+
+@module("mod1") @scope(("default", "x")) external fn: int => unit = "fn"
+@module("mod1") @scope("default") external value: int = "value"
+@module("mod1") @new @scope("default") external make: unit => {"a": int} = "Klass"
+@module("mod1") @scope("other") external other: int = "other"
+
+@module("mod2") @scope("default") external defaultOfDefault: int = "default"
+
+let f = () => fn(value + other + defaultOfDefault)
+let g = () => make()

tests/tests/src/scope_default_import.mjs

@@ -0,0 +1,19 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+
+import * as Mod1 from "mod1";
+import Mod1$1 from "mod1";
+import Mod2 from "mod2";
+
+function f() {
+  Mod1$1.x.fn((Mod1$1.value + Mod1.other.other | 0) + Mod2.default | 0);
+}
+
+function g() {
+  return new (Mod1$1.Klass)();
+}
+
+export {
+  f,
+  g,
+}
+/* mod1 Not a pure module */

tests/tests/src/scope_default_import.res

@@ -0,0 +1,11 @@
+// A leading "default" scope imports the module's default export
+
+@module("mod1") @scope(("default", "x")) external fn: int => unit = "fn"
+@module("mod1") @scope("default") external value: int = "value"
+@module("mod1") @new @scope("default") external make: unit => {"a": int} = "Klass"
+@module("mod1") @scope("other") external other: int = "other"
+
+@module("mod2") @scope("default") external defaultOfDefault: int = "default"
+
+let f = () => fn(value + other + defaultOfDefault)
+let g = () => make()