[vm/aot] Keep toString methods on exception classes in toString transformer
Flutter in google3 uses --delete-tostring-package-uri compiler option
to remove toString methods in package:flutter and dart:ui to reduce
size in release mode.
This has unfortunate effect of removing toString methods from exception
classes which may provide valuable information for investigating
problems seen in the wild.
This change adds a new @pragma('flutter:keep-to-string-in-subtypes')
on classes to keep toString methods on all subtypes of the annotated
classes. This pragma is now used on Exception and Error classes in
dart:core.
TEST=pkg/vm/test/transformations/to_string_transformer_test.dart
Issue: https://github.com/flutter/flutter/issues/61562
Change-Id: Ib739c83cdf6b539208f705ba198e63b8bc54fa61
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/227920
Reviewed-by: Dan Field <dnfield@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>
diff --git a/pkg/vm/lib/transformations/to_string_transformer.dart b/pkg/vm/lib/transformations/to_string_transformer.dart
index 0cd1b5f..824282d 100644
--- a/pkg/vm/lib/transformations/to_string_transformer.dart
+++ b/pkg/vm/lib/transformations/to_string_transformer.dart
@@ -19,6 +19,8 @@
/// 'package:flutter/foundation.dart'.
final Set<String> _packageUris;
+ final Map<Class, bool> _inheritedKeepAnnotations = {};
+
/// Turn 'dart:ui' into 'dart:ui', or
/// 'package:flutter/src/semantics_event.dart' into 'package:flutter'.
String _importUriToPackage(Uri importUri) =>
@@ -29,7 +31,18 @@
.contains(_importUriToPackage(node.enclosingLibrary.importUri));
}
- bool _hasKeepAnnotation(Procedure node) {
+ bool _hasKeepAnnotation(Procedure node) =>
+ _hasPragma(node, 'flutter:keep-to-string');
+
+ bool _hasKeepAnnotationOnClass(Class node) =>
+ _hasPragma(node, 'flutter:keep-to-string-in-subtypes');
+
+ bool _hasInheritedKeepAnnotation(Class node) =>
+ _inheritedKeepAnnotations[node] ??= (_hasKeepAnnotationOnClass(node) ||
+ node.supers
+ .any((Supertype t) => _hasInheritedKeepAnnotation(t.classNode)));
+
+ bool _hasPragma(Annotatable node, String pragma) {
for (ConstantExpression expression
in node.annotations.whereType<ConstantExpression>()) {
if (expression.constant is! InstanceConstant) {
@@ -43,8 +56,7 @@
for (var fieldRef in constant.fieldValues.keys) {
if (fieldRef.asField.name.text == 'name') {
Constant? name = constant.fieldValues[fieldRef];
- return name is StringConstant &&
- name.value == 'flutter:keep-to-string';
+ return name is StringConstant && name.value == pragma;
}
}
return false;
@@ -61,7 +73,8 @@
!node.isAbstract &&
!node.enclosingClass!.isEnum &&
_isInTargetPackage(node) &&
- !_hasKeepAnnotation(node)) {
+ !_hasKeepAnnotation(node) &&
+ !_hasInheritedKeepAnnotation(node.enclosingClass!)) {
node.function.body!.replaceWith(
ReturnStatement(
SuperMethodInvocation(
diff --git a/pkg/vm/testcases/transformations/to_string_transformer/lib/main.dart b/pkg/vm/testcases/transformations/to_string_transformer/lib/main.dart
index 96544f2..aa53235 100644
--- a/pkg/vm/testcases/transformations/to_string_transformer/lib/main.dart
+++ b/pkg/vm/testcases/transformations/to_string_transformer/lib/main.dart
@@ -5,6 +5,7 @@
import 'dart:convert';
const keepToString = pragma('flutter:keep-to-string');
+const keepToStringInSubtypes = pragma('flutter:keep-to-string-in-subtypes');
String toString() => 'I am static';
@@ -26,9 +27,28 @@
String toString() => 'I am a Keep';
}
+@keepToStringInSubtypes
+class Base1 {}
+
+class Base2 extends Base1 {}
+
+class Base3 extends Object with Base2 {}
+
+class KeepInherited implements Base3 {
+ @override
+ String toString() => 'Heir';
+}
+
+class MyException implements Exception {
+ @override
+ String toString() => 'A very detailed message';
+}
+
void main() {
final IFoo foo = Foo();
print(foo.toString());
print(Keep().toString());
print(FooEnum.B.toString());
+ print(KeepInherited().toString());
+ print(MyException().toString());
}
diff --git a/pkg/vm/testcases/transformations/to_string_transformer/not_transformed.expect b/pkg/vm/testcases/transformations/to_string_transformer/not_transformed.expect
index 29c959a..6d48b41 100644
--- a/pkg/vm/testcases/transformations/to_string_transformer/not_transformed.expect
+++ b/pkg/vm/testcases/transformations/to_string_transformer/not_transformed.expect
@@ -39,7 +39,45 @@
method toString() → core::String
return "I am a Keep";
}
+@#C16
+class Base1 extends core::Object {
+ synthetic constructor •() → self::Base1
+ : super core::Object::•()
+ ;
+}
+class Base2 extends self::Base1 {
+ synthetic constructor •() → self::Base2
+ : super self::Base1::•()
+ ;
+}
+abstract class _Base3&Object&Base2 extends core::Object implements self::Base2 /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/ {
+ const synthetic constructor •() → self::_Base3&Object&Base2
+ : super core::Object::•()
+ ;
+}
+class Base3 extends self::_Base3&Object&Base2 {
+ synthetic constructor •() → self::Base3
+ : super self::_Base3&Object&Base2::•()
+ ;
+}
+class KeepInherited extends core::Object implements self::Base3 {
+ synthetic constructor •() → self::KeepInherited
+ : super core::Object::•()
+ ;
+ @#C1
+ method toString() → core::String
+ return "Heir";
+}
+class MyException extends core::Object implements core::Exception {
+ synthetic constructor •() → self::MyException
+ : super core::Object::•()
+ ;
+ @#C1
+ method toString() → core::String
+ return "A very detailed message";
+}
static const field core::pragma keepToString = #C14;
+static const field core::pragma keepToStringInSubtypes = #C16;
static method toString() → core::String
return "I am static";
static method main() → void {
@@ -47,6 +85,8 @@
core::print(foo.{self::IFoo::toString}(){() → core::String});
core::print(new self::Keep::•().{self::Keep::toString}(){() → core::String});
core::print(#C7.{self::FooEnum::toString}(){() → core::String});
+ core::print(new self::KeepInherited::•().{self::KeepInherited::toString}(){() → core::String});
+ core::print(new self::MyException::•().{self::MyException::toString}(){() → core::String});
}
constants {
#C1 = core::_Override {}
@@ -63,4 +103,6 @@
#C12 = "flutter:keep-to-string"
#C13 = null
#C14 = core::pragma {name:#C12, options:#C13}
+ #C15 = "flutter:keep-to-string-in-subtypes"
+ #C16 = core::pragma {name:#C15, options:#C13}
}
diff --git a/pkg/vm/testcases/transformations/to_string_transformer/transformed.expect b/pkg/vm/testcases/transformations/to_string_transformer/transformed.expect
index dca5efb..75d87ae 100644
--- a/pkg/vm/testcases/transformations/to_string_transformer/transformed.expect
+++ b/pkg/vm/testcases/transformations/to_string_transformer/transformed.expect
@@ -39,7 +39,45 @@
method toString() → core::String
return "I am a Keep";
}
+@#C16
+class Base1 extends core::Object {
+ synthetic constructor •() → self::Base1
+ : super core::Object::•()
+ ;
+}
+class Base2 extends self::Base1 {
+ synthetic constructor •() → self::Base2
+ : super self::Base1::•()
+ ;
+}
+abstract class _Base3&Object&Base2 extends core::Object implements self::Base2 /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/ {
+ const synthetic constructor •() → self::_Base3&Object&Base2
+ : super core::Object::•()
+ ;
+}
+class Base3 extends self::_Base3&Object&Base2 {
+ synthetic constructor •() → self::Base3
+ : super self::_Base3&Object&Base2::•()
+ ;
+}
+class KeepInherited extends core::Object implements self::Base3 {
+ synthetic constructor •() → self::KeepInherited
+ : super core::Object::•()
+ ;
+ @#C1
+ method toString() → core::String
+ return "Heir";
+}
+class MyException extends core::Object implements core::Exception {
+ synthetic constructor •() → self::MyException
+ : super core::Object::•()
+ ;
+ @#C1
+ method toString() → core::String
+ return "A very detailed message";
+}
static const field core::pragma keepToString = #C14;
+static const field core::pragma keepToStringInSubtypes = #C16;
static method toString() → core::String
return "I am static";
static method main() → void {
@@ -47,6 +85,8 @@
core::print(foo.{self::IFoo::toString}(){() → core::String});
core::print(new self::Keep::•().{self::Keep::toString}(){() → core::String});
core::print(#C7.{self::FooEnum::toString}(){() → core::String});
+ core::print(new self::KeepInherited::•().{self::KeepInherited::toString}(){() → core::String});
+ core::print(new self::MyException::•().{self::MyException::toString}(){() → core::String});
}
constants {
#C1 = core::_Override {}
@@ -63,4 +103,6 @@
#C12 = "flutter:keep-to-string"
#C13 = null
#C14 = core::pragma {name:#C12, options:#C13}
+ #C15 = "flutter:keep-to-string-in-subtypes"
+ #C16 = core::pragma {name:#C15, options:#C13}
}
diff --git a/runtime/docs/pragmas.md b/runtime/docs/pragmas.md
index 589699c..77d6d8e 100644
--- a/runtime/docs/pragmas.md
+++ b/runtime/docs/pragmas.md
@@ -41,3 +41,14 @@
| Pragma | Meaning |
| --- | --- |
| `vm:testing.unsafe.trace-entrypoints-fn` | [Observing which flow-graph-level entry-point was used when a function was called](compiler/frontend/testing_trace_entrypoints_pragma.md) |
+
+## Flutter toString transformer pragmas
+
+These pragmas are useful to exclude certain toString methods from toString transformation,
+which is enabled with `--delete-tostring-package-uri` option in kernel compilers and
+used by Flutter to remove certain toString methods in release mode to reduce size.
+
+| Pragma | Meaning |
+| --- | --- |
+| `flutter:keep-to-string` | Avoid transforming the annotated toString method. |
+| `flutter:keep-to-string-in-subtypes` | Avoid transforming toString methods in all subtypes of the annotated class. |
diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
index 6190c83..00d69ce 100644
--- a/sdk/lib/core/errors.dart
+++ b/sdk/lib/core/errors.dart
@@ -64,6 +64,7 @@
/// For example, the [String.contains] method will use a [RangeError]
/// if its `startIndex` isn't in the range `0..length`,
/// which is easily created by `RangeError.range(startIndex, 0, length)`.
+@pragma('flutter:keep-to-string-in-subtypes')
class Error {
Error(); // Prevent use as mixin.
diff --git a/sdk/lib/core/exceptions.dart b/sdk/lib/core/exceptions.dart
index 889c991..f522d27 100644
--- a/sdk/lib/core/exceptions.dart
+++ b/sdk/lib/core/exceptions.dart
@@ -16,6 +16,7 @@
/// is discouraged in library code since it doesn't give users a precise
/// type they can catch. It may be reasonable to use instances of this
/// class in tests or during development.
+@pragma('flutter:keep-to-string-in-subtypes')
abstract class Exception {
factory Exception([var message]) => _Exception(message);
}
