[ddc, dart2js] readd dart:mirrors

Technically almost no user of ddc should be able to reach this compile-time error if they are using webdev (it appears a couple users do invoke it directly, though).  Project sass demonstrated that users of dart2js can notice this breaking change.

Given that we are bundling many breaking changes for null-safety on the next release, it seems like making imports to dart:mirrors a compile-time error is not strictly necessary at this time.

One idea is to change this to a compile-time error in our tools when users opt-in their libraries or when they enable strong null-safety mode.

Change-Id: I7f12657eba508e2d071dda60087a21475a303d9f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/139494
Reviewed-by: Nicholas Shahan <nshahan@google.com>
Commit-Queue: Sigmund Cherem <sigmund@google.com>

CHANGELOG.md

@@ -113,10 +113,14 @@ additional details see the [announcement].
   `external`. Previously the external could be omitted in some cases with DDC
   but doing so would cause incorrect behavior with `dart2js`.
 * JS interop classes with an index operator are now static errors.
-* Removed the `dart:mirrors` library from the SDK. Use of this library on the
-  web has been unsupported and prevented by the Dart build systems since Dart
-  v2.0.0. All known exception cases have been cleaned up. This change makes DDC
-  and dart2js now issue a compile-time error directly as well.
+* All remaining support from the `dart:mirrors` library has been removed.
+  Use of this library on the web has been unsupported and prevented by the Dart
+  build systems since Dart v2.0.0. All known exception cases have been cleaned
+  up. This change makes DDC and dart2js now behave consistently.
+  
+  The library can still be imported on web apps, but all APIs throw. In a future
+  breaking change release, imports to this library will likely become a
+  compile-time error.
 
  [announcement]: https://github.com/dart-lang/sdk/issues/38994
 
@@ -128,10 +132,6 @@ additional details see the [announcement].
   forgiving. Corresponding type parameter bounds now only need to be mutual
   subtypes rather than structurally equal up to renaming of bound type variables
   and equating all top types.
-* Removed the `dart:mirrors` library from the SDK. Use of this library on the
-  web has been unsupported and prevented by the Dart build systems since Dart
-  v2.0.0. All known exception cases have been cleaned up. This change makes DDC
-  and dart2js now issue a compile-time error directly as well.
 * **Breaking Change**: Types are now normalized. See [normalization] for the
   full specification. Types will now be printed in their normal form, and
   mutual subtypes with the same normal form will now be considered equal.

sdk/lib/_internal/js_runtime/lib/mirrors_patch_cfe.dart

@@ -24,3 +24,23 @@ ClassMirror reflectClass(Type key) => throw new UnsupportedError(_message);
 @patch
 TypeMirror reflectType(Type key, [List<Type> typeArguments]) =>
     throw new UnsupportedError(_message);
+
+@patch
+abstract class MirrorSystem {
+  Map<Uri, LibraryMirror> get libraries;
+  IsolateMirror get isolate;
+  TypeMirror get dynamicType;
+  TypeMirror get voidType;
+  TypeMirror get neverType;
+
+  @patch
+  LibraryMirror findLibrary(Symbol libraryName) =>
+      throw new UnsupportedError(_message);
+
+  @patch
+  static String getName(Symbol symbol) => throw new UnsupportedError(_message);
+
+  @patch
+  static Symbol getSymbol(String name, [LibraryMirror library]) =>
+      throw new UnsupportedError(_message);
+}

sdk/lib/libraries.json

@@ -217,6 +217,11 @@
         "uri": "math/math.dart",
         "patches": "_internal/js_runtime/lib/math_patch.dart"
       },
+      "mirrors": {
+        "uri": "mirrors/mirrors.dart",
+        "patches": "_internal/js_runtime/lib/mirrors_patch_cfe.dart",
+        "supported": false
+      },
       "typed_data": {
         "uri": "typed_data/typed_data.dart",
         "patches": "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -322,6 +327,11 @@
         "uri": "math/math.dart",
         "patches": "_internal/js_runtime/lib/math_patch.dart"
       },
+      "mirrors": {
+        "uri": "mirrors/mirrors.dart",
+        "patches": "_internal/js_runtime/lib/mirrors_patch_cfe.dart",
+        "supported": false
+      },
       "typed_data": {
         "uri": "typed_data/typed_data.dart",
         "patches": "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -428,6 +438,11 @@
         "patches": "_internal/js_dev_runtime/patch/isolate_patch.dart",
         "supported": false
       },
+      "mirrors": {
+        "uri": "mirrors/mirrors.dart",
+        "patches": "_internal/js_runtime/lib/mirrors_patch_cfe.dart",
+        "supported": false
+      },
       "math": {
         "uri": "math/math.dart",
         "patches": "_internal/js_dev_runtime/patch/math_patch.dart"

sdk/lib/libraries.yaml

@@ -214,6 +214,11 @@ dart2js:
       uri: "math/math.dart"
       patches: "_internal/js_runtime/lib/math_patch.dart"
 
+    mirrors:
+      uri: "mirrors/mirrors.dart"
+      patches: "_internal/js_runtime/lib/mirrors_patch_cfe.dart"
+      supported: false
+
     typed_data:
       uri: "typed_data/typed_data.dart"
       patches: "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -317,6 +322,11 @@ dart2js_server:
       uri: "math/math.dart"
       patches: "_internal/js_runtime/lib/math_patch.dart"
 
+    mirrors:
+      uri: "mirrors/mirrors.dart"
+      patches: "_internal/js_runtime/lib/mirrors_patch_cfe.dart"
+      supported: false
+
     typed_data:
       uri: "typed_data/typed_data.dart"
       patches: "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -421,6 +431,11 @@ dartdevc:
         patches: "_internal/js_dev_runtime/patch/isolate_patch.dart"
         supported: false
 
+      mirrors:
+        uri: "mirrors/mirrors.dart"
+        patches: "_internal/js_runtime/lib/mirrors_patch_cfe.dart"
+        supported: false
+
       math:
         uri: "math/math.dart"
         patches: "_internal/js_dev_runtime/patch/math_patch.dart"

sdk_nnbd/lib/_internal/js_runtime/lib/mirrors_patch_cfe.dart

@@ -0,0 +1,44 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Patch library for dart:mirrors.
+
+import 'dart:_js_helper' show patch;
+import 'dart:mirrors';
+
+const String _message = 'dart:mirrors is no longer supported for web apps';
+
+@patch
+MirrorSystem currentMirrorSystem() => throw new UnsupportedError(_message);
+
+@patch
+InstanceMirror reflect(dynamic reflectee) =>
+    throw new UnsupportedError(_message);
+
+@patch
+ClassMirror reflectClass(Type key) => throw new UnsupportedError(_message);
+
+@patch
+TypeMirror reflectType(Type key, [List<Type> typeArguments]) =>
+    throw new UnsupportedError(_message);
+
+@patch
+abstract class MirrorSystem {
+  Map<Uri, LibraryMirror> get libraries;
+  IsolateMirror get isolate;
+  TypeMirror get dynamicType;
+  TypeMirror get voidType;
+  TypeMirror get neverType;
+
+  @patch
+  LibraryMirror findLibrary(Symbol libraryName) =>
+      throw new UnsupportedError(_message);
+
+  @patch
+  static String getName(Symbol symbol) => throw new UnsupportedError(_message);
+
+  @patch
+  static Symbol getSymbol(String name, [LibraryMirror library]) =>
+      throw new UnsupportedError(_message);
+}

sdk_nnbd/lib/libraries.json

@@ -217,6 +217,11 @@
         "uri": "math/math.dart",
         "patches": "_internal/js_runtime/lib/math_patch.dart"
       },
+      "mirrors": {
+        "uri": "mirrors/mirrors.dart",
+        "patches": "_internal/js_runtime/lib/mirrors_patch_cfe.dart",
+        "supported": false
+      },
       "typed_data": {
         "uri": "typed_data/typed_data.dart",
         "patches": "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -322,6 +327,11 @@
         "uri": "math/math.dart",
         "patches": "_internal/js_runtime/lib/math_patch.dart"
       },
+      "mirrors": {
+        "uri": "mirrors/mirrors.dart",
+        "patches": "_internal/js_runtime/lib/mirrors_patch_cfe.dart",
+        "supported": false
+      },
       "typed_data": {
         "uri": "typed_data/typed_data.dart",
         "patches": "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -428,6 +438,11 @@
         "patches": "_internal/js_dev_runtime/patch/isolate_patch.dart",
         "supported": false
       },
+      "mirrors": {
+        "uri": "mirrors/mirrors.dart",
+        "patches": "_internal/js_runtime/lib/mirrors_patch_cfe.dart",
+        "supported": false
+      },
       "math": {
         "uri": "math/math.dart",
         "patches": "_internal/js_dev_runtime/patch/math_patch.dart"

sdk_nnbd/lib/libraries.yaml

@@ -214,6 +214,11 @@ dart2js:
       uri: "math/math.dart"
       patches: "_internal/js_runtime/lib/math_patch.dart"
 
+    mirrors:
+      uri: "mirrors/mirrors.dart"
+      patches: "_internal/js_runtime/lib/mirrors_patch_cfe.dart"
+      supported: false
+
     typed_data:
       uri: "typed_data/typed_data.dart"
       patches: "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -317,6 +322,11 @@ dart2js_server:
       uri: "math/math.dart"
       patches: "_internal/js_runtime/lib/math_patch.dart"
 
+    mirrors:
+      uri: "mirrors/mirrors.dart"
+      patches: "_internal/js_runtime/lib/mirrors_patch_cfe.dart"
+      supported: false
+
     typed_data:
       uri: "typed_data/typed_data.dart"
       patches: "_internal/js_runtime/lib/typed_data_patch.dart"
@@ -421,6 +431,11 @@ dartdevc:
         patches: "_internal/js_dev_runtime/patch/isolate_patch.dart"
         supported: false
 
+      mirrors:
+        uri: "mirrors/mirrors.dart"
+        patches: "_internal/js_runtime/lib/mirrors_patch_cfe.dart"
+        supported: false
+
       math:
         uri: "math/math.dart"
         patches: "_internal/js_dev_runtime/patch/math_patch.dart"