[gjs/esm/dynamic-imports: 4/6] WIP - add dynamic import support to scripts

[Evan Welsh <ewlsh src gnome org>]

commit a6c5ff345556bf914f85460685c7e1eeb5600b1f
Author: Evan Welsh <contact evanwelsh com>
Date:   Fri Feb 5 21:51:41 2021 -0800

    WIP - add dynamic import support to scripts
    
    To allow import() from scripts we must set script privates
    with a object similar to the ModulePrivate class.

 gjs/context.cpp                     |  8 ++++++++
 gjs/module.cpp                      | 38 +++++++++++++++++++++++++++++++++++--
 gjs/module.h                        |  3 +++
 installed-tests/js/testESModules.js | 19 +++++++++----------
 4 files changed, 56 insertions(+), 12 deletions(-)
---
diff --git a/gjs/context.cpp b/gjs/context.cpp
index 1a85f6c6..01565595 100644
--- a/gjs/context.cpp
+++ b/gjs/context.cpp
@@ -1249,6 +1249,14 @@ bool GjsContextPrivate::eval_with_scope(JS::HandleObject scope_object,
     JS::CompileOptions options(m_cx);
     options.setFileAndLine(filename, 1);
 
+    GjsAutoUnref<GFile> file = g_file_new_for_commandline_arg(filename);
+    GjsAutoChar uri = g_file_get_uri(file);
+    JS::RootedObject priv(m_cx, gjs_script_module_build_private(m_cx, uri));
+    if (!priv)
+        return false;
+
+    options.setPrivateValue(JS::ObjectValue(*priv));
+
     if (!JS::Evaluate(m_cx, scope_chain, options, buf, retval))
         return false;
 
diff --git a/gjs/module.cpp b/gjs/module.cpp
index 9645e134..ed6b97de 100644
--- a/gjs/module.cpp
+++ b/gjs/module.cpp
@@ -92,7 +92,7 @@ class GjsScriptModule {
     GJS_JSAPI_RETURN_CONVENTION
     bool evaluate_import(JSContext* cx, JS::HandleObject module,
                          const char* script, ssize_t script_len,
-                         const char* filename) {
+                         const char* filename, const char* uri) {
         std::u16string utf16_string =
             gjs_utf8_script_to_utf16(script, script_len);
         // COMPAT: This could use JS::SourceText<mozilla::Utf8Unit> directly,
@@ -112,6 +112,9 @@ class GjsScriptModule {
         JS::CompileOptions options(cx);
         options.setFileAndLine(filename, 1);
 
+        JS::RootedObject priv(cx, build_private(cx, uri));
+        options.setPrivateValue(JS::ObjectValue(*priv));
+
         JS::RootedValue ignored_retval(cx);
         if (!JS::Evaluate(cx, scope_chain, options, buf, &ignored_retval))
             return false;
@@ -143,7 +146,8 @@ class GjsScriptModule {
         g_assert(script);
 
         GjsAutoChar full_path = g_file_get_parse_name(file);
-        return evaluate_import(cx, module, script, script_len, full_path);
+        GjsAutoChar uri = g_file_get_uri(file);
+        return evaluate_import(cx, module, script, script_len, full_path, uri);
     }
 
     /* JSClass operations */
@@ -213,6 +217,21 @@ class GjsScriptModule {
     };
 
  public:
+    /* 
+     * Creates a JS object to pass to JS::CompileOptions as a script's private.
+     */
+    [[nodiscard]] static JSObject* build_private(JSContext* cx, const char* script_uri) {
+        JS::RootedObject priv(cx, JS_NewPlainObject(cx));
+        const GjsAtoms& atoms = GjsContextPrivate::atoms(cx);
+
+        JS::RootedValue val(cx);
+        if (!gjs_string_from_utf8(cx, script_uri, &val) ||
+            !JS_SetPropertyById(cx, priv, atoms.uri(), val))
+            return nullptr;
+
+        return priv;
+    }
+
     /* Carries out the import operation */
     GJS_JSAPI_RETURN_CONVENTION
     static JSObject *
@@ -232,6 +251,21 @@ class GjsScriptModule {
     }
 };
 
+/**
+ * gjs_script_module_build_private:
+ * @param cx the #JSContext
+ * @param uri the URI this script module is loaded from
+ * 
+ * @brief To support dynamic imports from scripts, we need to provide private
+ * data when we compile scripts which is compatible with our module resolution
+ * hooks in modules/internal/loader.js
+ * 
+ * @returns a JSObject which can be used for a JSScript's private data.
+ */
+JSObject* gjs_script_module_build_private(JSContext* cx, const char* uri) {
+    return GjsScriptModule::build_private(cx, uri);
+}
+
 /**
  * gjs_module_import:
  * @cx: the JS context
diff --git a/gjs/module.h b/gjs/module.h
index d303530f..dbe088ec 100644
--- a/gjs/module.h
+++ b/gjs/module.h
@@ -21,6 +21,9 @@ gjs_module_import(JSContext       *cx,
                   const char      *name,
                   GFile           *file);
 
+GJS_JSAPI_RETURN_CONVENTION
+JSObject* gjs_script_module_build_private(JSContext* cx, const char* uri);
+
 GJS_JSAPI_RETURN_CONVENTION
 JSObject* gjs_get_native_registry(JSObject* global);
 
diff --git a/installed-tests/js/testESModules.js b/installed-tests/js/testESModules.js
index 6b5afa40..bdc1a89f 100644
--- a/installed-tests/js/testESModules.js
+++ b/installed-tests/js/testESModules.js
@@ -80,21 +80,20 @@ describe('Builtin ES modules', function () {
 
 describe('Dynamic imports', function () {
     let module;
-    beforeEach(function (done) {
-        import('resource:///org/gjs/jsunit/modules/say.js')
-            .then(m => (module = m))
-            .catch(err => {
-                logError(err);
-                fail();
-            })
-            .finally(done);
+    beforeEach(async function () {
+        try {
+            module = await import('resource:///org/gjs/jsunit/modules/say.js')
+        } catch(err) {
+            logError(err);
+            fail();
+        }
     });
 
-    it('default import', function () {
+    it('default import', async function () {
         expect(module.default()).toEqual('default export');
     });
 
-    it('named import', function () {
+    it('named import', async function () {
         expect(module.say('hi')).toEqual('<( hi )');
     });
 });