Add a @JSExportName annotation for internal use in the runtime (use it to export dart.assert instead of assert_)

BUG=
[email protected]

Review URL: https://codereview.chromium.org/1580413002 .

Author: Olivier Chafik

pkg/dev_compiler/lib/runtime/dart/_classes.js

@@ -20,7 +20,7 @@ dart_library.library('dart/_classes', null, /* Imports */[
 ], function(exports, dart_utils, core, _interceptors, types, rtti) {
   'use strict';
 
-  const assert = dart_utils.assert_;
+  const assert = dart_utils.assert;
   const copyProperties = dart_utils.copyProperties;
   const copyTheseProperties = dart_utils.copyTheseProperties;
   const defineMemoizedGetter = dart_utils.defineMemoizedGetter;

pkg/dev_compiler/lib/runtime/dart/_foreign_helper.js

@@ -20,6 +20,14 @@ dart_library.library('dart/_foreign_helper', null, /* Imports */[
     if (arg11 === void 0) arg11 = null;
   }
   dart.fn(JS, dart.dynamic, [core.String, core.String], [dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic]);
+  class JSExportName extends core.Object {
+    JSExportName(name) {
+      this.name = name;
+    }
+  }
+  dart.setSignature(JSExportName, {
+    constructors: () => ({JSExportName: [JSExportName, [core.String]]})
+  });
   function JS_CURRENT_ISOLATE_CONTEXT() {
   }
   dart.fn(JS_CURRENT_ISOLATE_CONTEXT, () => dart.definiteFunctionType(IsolateContext, []));
@@ -111,6 +119,7 @@ dart_library.library('dart/_foreign_helper', null, /* Imports */[
   dart.fn(JS_STRING_CONCAT, core.String, [core.String, core.String]);
   // Exports:
   exports.JS = JS;
+  exports.JSExportName = JSExportName;
   exports.JS_CURRENT_ISOLATE_CONTEXT = JS_CURRENT_ISOLATE_CONTEXT;
   exports.IsolateContext = IsolateContext;
   exports.JS_CALL_IN_ISOLATE = JS_CALL_IN_ISOLATE;

pkg/dev_compiler/lib/runtime/dart/_types.js

@@ -16,7 +16,7 @@ dart_library.library('dart/_types', null, /* Imports */[
 
   const getOwnPropertyNames = Object.getOwnPropertyNames;
 
-  const assert = dart_utils.assert_;
+  const assert = dart_utils.assert;
 
   /**
    * Types in dart are represented at runtime as follows.

pkg/dev_compiler/lib/runtime/dart/_utils.js

@@ -22,7 +22,7 @@ dart_library.library('dart/_utils', null, /* Imports */[
   function throwInternalError(message) {
     throw Error(message);
   }
-  function assert_(condition) {
+  function assert(condition) {
     if (!condition) throwInternalError("The compiler is broken: failed assert");
   }
   function getOwnNamesAndSymbols(obj) {
@@ -95,7 +95,7 @@ dart_library.library('dart/_utils', null, /* Imports */[
   exports.StrongModeError = StrongModeError;
   exports.throwStrongModeError = throwStrongModeError;
   exports.throwInternalError = throwInternalError;
-  exports.assert_ = assert_;
+  exports.assert = assert;
   exports.getOwnNamesAndSymbols = getOwnNamesAndSymbols;
   exports.safeGetOwnProperty = safeGetOwnProperty;
   exports.defineLazyProperty = defineLazyProperty;

pkg/dev_compiler/lib/src/codegen/js_codegen.dart

@@ -1294,6 +1294,17 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
         node.element);
   }
 
+  /// Returns the name value of the `JSExportName` annotation (when compiling
+  /// the SDK), or `null` if there's none. This is used to control the name
+  /// under which functions are compiled and exported.
+  String _getJSExportName(Element e) {
+    if (e is! FunctionElement || !currentLibrary.source.isInSystemLibrary) {
+      return null;
+    }
+    var jsName = findAnnotation(e, isJSExportNameAnnotation);
+    return getConstantField(jsName, 'name', types.stringType)?.toStringValue();
+  }
+
   @override
   JS.Statement visitFunctionDeclaration(FunctionDeclaration node) {
     assert(node.parent is CompilationUnit);
@@ -1309,7 +1320,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
     var body = <JS.Statement>[];
     _flushLibraryProperties(body);
 
-    var name = node.name.name;
+    var name = _getJSExportName(node.element) ?? node.name.name;
 
     var fn = _visit(node.functionExpression);
     bool needsTagging = true;
@@ -1575,8 +1586,6 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
 
     _loader.declareBeforeUse(element);
 
-    var name = element.name;
-
     // type literal
     if (element is ClassElement ||
         element is DynamicElementImpl ||
@@ -1587,9 +1596,11 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
 
     // library member
     if (element.enclosingElement is CompilationUnitElement) {
-      return _maybeQualifiedName(element);
+      return _emitTopLevelName(element);
     }
 
+    var name = element.name;
+
     // Unqualified class member. This could mean implicit-this, or implicit
     // call to a static from the same class.
     if (element is ClassMemberElement && element is! ConstructorElement) {
@@ -1757,17 +1768,17 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
         jsArgs = [];
       }
       if (jsArgs != null) {
-        var genericName = _maybeQualifiedName(element, '$name\$');
+        var genericName = _emitTopLevelName(element, suffix: '\$');
         return js.call('#(#)', [genericName, jsArgs]);
       }
     }
 
-    return _maybeQualifiedName(element);
+    return _emitTopLevelName(element);
   }
 
-  JS.Expression _maybeQualifiedName(Element e, [String name]) {
+  JS.Expression _emitTopLevelName(Element e, {String suffix : ''}) {
     var libName = _libraryName(e.library);
-    var nameExpr = _propertyName(name ?? e.name);
+    var nameExpr = _propertyName((_getJSExportName(e) ?? e.name) + suffix);
 
     // Always qualify:
     // * mutable top-level fields
@@ -2231,6 +2242,9 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ClosureAnnotator {
     if (isJSTopLevel) eagerInit = true;
 
     var fieldName = field.name.name;
+    if (element is TopLevelVariableElement) {
+      fieldName = _getJSExportName(element) ?? fieldName;
+    }
     if ((field.isConst && eagerInit && element is TopLevelVariableElement) ||
         isJSTopLevel) {
       // constant fields don't change, so we can generate them as `let`

pkg/dev_compiler/lib/src/codegen/js_interop.dart

@@ -11,21 +11,40 @@ import 'package:analyzer/src/generated/constant.dart';
 bool _isJsLibType(String expectedName, Element e) =>
     e?.name == expectedName && _isJsLib(e.library);
 
+/// Returns true if [e] represents any library from `package:js` or is the
+/// internal `dart:_js_helper` library.
 bool _isJsLib(LibraryElement e) {
-  var libName = e?.name;
-  return libName == 'js' ||
-      libName == 'js.varargs' ||
-      libName == 'dart._js_helper';
+  if (e == null) return false;
+  var uri = e.source.uri;
+  if (uri.scheme == 'package' && uri.path.startsWith('js/')) return true;
+  if (uri.scheme == 'dart') {
+    return uri.path == '_js_helper' || uri.path == '_foreign_helper';
+  }
+  return false;
 }
 
+/// Whether [value] is a `@rest` annotation (to be used on function parameters
+/// to have them compiled as `...` rest params in ES6 outputs).
 bool isJsRestAnnotation(DartObjectImpl value) =>
     _isJsLibType('_Rest', value.type.element);
 
+/// Whether [i] is a `spread` invocation (to be used on function arguments
+/// to have them compiled as `...` spread args in ES6 outputs).
 bool isJsSpreadInvocation(MethodInvocation i) =>
     _isJsLibType('spread', i.methodName?.bestElement);
 
 // TODO(jmesserly): Move JsPeerInterface to package:js (see issue #135).
-bool isJSAnnotation(DartObjectImpl value) => value.type.name == 'JS';
+bool isJSAnnotation(DartObjectImpl value) =>
+    _isJsLibType('JS', value.type.element);
+
+/// Whether [value] is a `@JSExportName` (internal annotation used in SDK
+/// instead of `@JS` from `package:js`).
+bool isJSExportNameAnnotation(DartObjectImpl value) {
+  var e = value?.type?.element;
+  if (e?.name != 'JSExportName') return false;
+  var uri = e.source.uri;
+  return uri.scheme == 'dart' && uri.path == '_foreign_helper';
+}
 
 bool isJsPeerInterface(DartObjectImpl value) =>
     value.type.name == 'JsPeerInterface';

pkg/dev_compiler/tool/input_sdk/private/foreign_helper.dart

@@ -110,6 +110,15 @@ JS(String typeDescription, String codeTemplate,
     [arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11])
 {}
 
+/// Annotates the compiled Js name for fields and methods.
+/// Similar behaviour to `JS` from `package:js/js.dart` (but usable from runtime
+/// files), and not to be confused with `JSName` from `js_helper` (which deals
+/// with names of externs).
+class JSExportName {
+  final String name;
+  const JSExportName(this.name);
+}
+
 /**
  * Returns the isolate in which this code is running.
  */

pkg/dev_compiler/tool/input_sdk/private/utils.dart

@@ -4,7 +4,7 @@
 
 library dart._utils;
 
-import 'dart:_foreign_helper' show JS;
+import 'dart:_foreign_helper' show JS, JSExportName;
 
 /// This library defines a set of general javascript utilities for us
 /// by the Dart runtime.
@@ -39,6 +39,7 @@ void throwInternalError(String message) => JS('', '''(() => {
 
 // TODO(ochafik): Re-introduce a @JS annotation in the SDK (same as package:js)
 // so that this is named 'assert' in JavaScript.
+@JSExportName('assert')
 void assert_(bool condition) => JS('', '''(() => {
   if (!condition) throwInternalError("The compiler is broken: failed assert");
 })()''');