[analysis_server] Add ColorComputer for locating color references in user code

Change-Id: I166f87135a9b15821e5f65cfea33b8a15fa7aa03
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/219101
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/computer/computer_color.dart

@@ -0,0 +1,361 @@
+// Copyright (c) 2021, 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.
+
+import 'package:analysis_server/src/utilities/flutter.dart';
+import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/constant/value.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/src/dart/constant/value.dart' show GenericState;
+import 'package:analyzer/src/dart/element/inheritance_manager3.dart';
+import 'package:analyzer/src/dart/element/type_system.dart';
+import 'package:analyzer/src/lint/linter.dart';
+import 'package:collection/collection.dart';
+
+/// Computer for dart:ui/Flutter Color references.
+class ColorComputer {
+  final ResolvedUnitResult resolvedUnit;
+  final LinterContext _linterContext;
+  final List<ColorReference> _colors = [];
+  final Flutter _flutter = Flutter.instance;
+
+  ColorComputer(this.resolvedUnit)
+      : _linterContext = LinterContextImpl(
+          [], // unused
+          LinterContextUnit(resolvedUnit.content, resolvedUnit.unit),
+          resolvedUnit.session.declaredVariables,
+          resolvedUnit.typeProvider,
+          resolvedUnit.typeSystem as TypeSystemImpl,
+          InheritanceManager3(), // unused
+          resolvedUnit.session.analysisContext.analysisOptions,
+          null,
+        );
+
+  /// Returns information about the color references in [resolvedUnit].
+  ///
+  /// This method should only be called once for any instance of this class.
+  List<ColorReference> compute() {
+    final visitor = _ColorBuilder(this);
+    resolvedUnit.unit.accept(visitor);
+    return _colors;
+  }
+
+  /// Tries to add a color for the [expression].
+  ///
+  /// If [target] is supplied, will be used instead of [expression] allowing
+  /// a value to be read from the member [memberName] or from a swatch value
+  /// with index [index].
+  bool tryAddColor(
+    Expression expression, {
+    Expression? target,
+    String? memberName,
+    int? index,
+  }) {
+    if (!_isColor(expression.staticType)) return false;
+
+    target ??= expression;
+
+    // Try to evaluate the constant target.
+    final colorConstResult = _linterContext.evaluateConstant(target);
+    var colorConst = colorConstResult.value;
+    if (colorConstResult.errors.isNotEmpty || colorConst == null) return false;
+
+    // If we want a specific member or swatch index, read that.
+    if (memberName != null) {
+      colorConst = _getMember(colorConst, memberName);
+    } else if (index != null) {
+      colorConst = _getSwatchValue(colorConst, index);
+    }
+
+    return _tryRecordColor(expression, colorConst);
+  }
+
+  /// Tries to add a color for the instance creation [expression].
+  ///
+  /// This handles constructor calls that cannot be evaluated (for example
+  /// because they are not const) but are simple well-known dart:ui/Flutter
+  /// color constructors that we can manually parse.
+  bool tryAddKnownColorConstructor(InstanceCreationExpression expression) {
+    if (!_isColor(expression.staticType)) return false;
+
+    final constructor = expression.constructorName;
+    final staticElement = constructor.staticElement;
+    final classElement = staticElement?.enclosingElement;
+    final className = classElement?.name;
+    final constructorName = constructor.name?.name;
+    final constructorArgs = expression.argumentList.arguments
+        .map((e) => e is Literal ? e : null)
+        .toList();
+
+    int? colorValue;
+    if (_isDartUi(classElement) && className == 'Color') {
+      colorValue = _getDartUiColorValue(constructorName, constructorArgs);
+    } else if (_isFlutterPainting(classElement) && className == 'ColorSwatch') {
+      colorValue =
+          _getFlutterSwatchColorValue(constructorName, constructorArgs);
+    } else if (_isFlutterMaterial(classElement) &&
+        className == 'MaterialAccentColor') {
+      colorValue =
+          _getFlutterMaterialAccentColorValue(constructorName, constructorArgs);
+    }
+
+    return _tryRecordColorValue(expression, colorValue);
+  }
+
+  /// Creates a [ColorInformation] by extracting the argb values from
+  /// [value] encoded as 0xAARRGGBB as in the dart:ui Color class.
+  ColorInformation _colorInformationForColorValue(int value) {
+    // Extract color information according to dart:ui Color values.
+    final alpha = (0xff000000 & value) >> 24;
+    final red = (0x00ff0000 & value) >> 16;
+    final blue = (0x000000ff & value) >> 0;
+    final green = (0x0000ff00 & value) >> 8;
+
+    return ColorInformation(alpha, red, green, blue);
+  }
+
+  /// Extracts the integer color value from the dart:ui Color constant [color].
+  int? _colorValueForColorConst(DartObject? color) {
+    if (color == null || color.isNull) return null;
+
+    // If the object has a "color" field, walk down to that, because some colors
+    // like CupertinoColors have a "value=0" with an overridden getter that
+    // would always result in a value representing black.
+    color = color.getFieldFromHierarchy('color') ?? color;
+
+    return color.getFieldFromHierarchy('value')?.toIntValue();
+  }
+
+  /// Converts ARGB values into a single int value as 0xAARRGGBB as used by
+  /// the dart:ui Color class.
+  int _colorValueForComponents(int alpha, int red, int green, int blue) {
+    return (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
+  }
+
+  /// Extracts the color value from dart:ui Color constructor args.
+  int? _getDartUiColorValue(String? name, List<Literal?> args) {
+    if (name == null && args.length == 1) {
+      final arg0 = args[0];
+      return arg0 is IntegerLiteral ? arg0.value : null;
+    } else if (name == 'fromARGB' && args.length == 4) {
+      final arg0 = args[0];
+      final arg1 = args[1];
+      final arg2 = args[2];
+      final arg3 = args[3];
+
+      final alpha = arg0 is IntegerLiteral ? arg0.value : null;
+      final red = arg1 is IntegerLiteral ? arg1.value : null;
+      final green = arg2 is IntegerLiteral ? arg2.value : null;
+      final blue = arg3 is IntegerLiteral ? arg3.value : null;
+
+      return alpha != null && red != null && green != null && blue != null
+          ? _colorValueForComponents(alpha, red, green, blue)
+          : null;
+    } else if (name == 'fromRGBO' && args.length == 4) {
+      final arg0 = args[0];
+      final arg1 = args[1];
+      final arg2 = args[2];
+      final arg3 = args[3];
+
+      final red = arg0 is IntegerLiteral ? arg0.value : null;
+      final green = arg1 is IntegerLiteral ? arg1.value : null;
+      final blue = arg2 is IntegerLiteral ? arg2.value : null;
+      final opacity = arg3 is IntegerLiteral
+          ? arg3.value
+          : arg3 is DoubleLiteral
+              ? arg3.value
+              : null;
+      final alpha = opacity != null ? (opacity * 255).toInt() : null;
+
+      return alpha != null && red != null && green != null && blue != null
+          ? _colorValueForComponents(alpha, red, green, blue)
+          : null;
+    }
+  }
+
+  /// Extracts the color value from Flutter MaterialAccentColor constructor args.
+  int? _getFlutterMaterialAccentColorValue(String? name, List<Literal?> args) =>
+      // MaterialAccentColor is a subclass of SwatchColor and has the same
+      // constructor.
+      _getFlutterSwatchColorValue(name, args);
+
+  /// Extracts the color value from Flutter ColorSwatch constructor args.
+  int? _getFlutterSwatchColorValue(String? name, List<Literal?> args) {
+    if (name == null && args.isNotEmpty) {
+      final arg0 = args[0];
+      return arg0 is IntegerLiteral ? arg0.value : null;
+    }
+  }
+
+  /// Extracts a named member from a color.
+  ///
+  /// Well-known getters like `shade500` will be mapped onto the swatch value
+  /// with a matching index.
+  DartObject? _getMember(DartObject target, String memberName) {
+    final colorValue = target.getFieldFromHierarchy(memberName);
+    if (colorValue != null) {
+      return colorValue;
+    }
+
+    // If we didn't get a value but it's a getter we know how to read from a
+    // swatch, try that.
+    if (memberName.startsWith('shade')) {
+      final shadeNumber = int.tryParse(memberName.substring(5));
+      if (shadeNumber != null) {
+        return _getSwatchValue(target, shadeNumber);
+      }
+    }
+  }
+
+  /// Extracts a specific shade index from a Flutter SwatchColor.
+  DartObject? _getSwatchValue(DartObject target, int swatchValue) {
+    final swatch = target.getFieldFromHierarchy('_swatch')?.toMapValue();
+    if (swatch == null) return null;
+
+    final key = swatch.keys.firstWhereOrNull(
+      (key) => key?.toIntValue() == swatchValue,
+    );
+    if (key == null) return null;
+
+    return swatch[key];
+  }
+
+  /// Checks whether [type] is - or extends - the dart:ui Color class.
+  bool _isColor(DartType? type) => type != null && _flutter.isColor(type);
+
+  /// Checks whether this elements library is dart:ui.
+  bool _isDartUi(Element? element) => element?.library?.name == 'dart.ui';
+
+  /// Checks whether this elements library is Flutter Material colors.
+  bool _isFlutterMaterial(Element? element) =>
+      element?.library?.identifier ==
+      'package:flutter/src/material/colors.dart';
+
+  /// Checks whether this elements library is Flutter Painting colors.
+  bool _isFlutterPainting(Element? element) =>
+      element?.library?.identifier ==
+      'package:flutter/src/painting/colors.dart';
+
+  /// Tries to record a color value from [colorConst] for [expression].
+  ///
+  /// Returns whether a valid color was found and recorded.
+  bool _tryRecordColor(Expression expression, DartObject? colorConst) =>
+      _tryRecordColorValue(expression, _colorValueForColorConst(colorConst));
+
+  /// Tries to record the [colorValue] for [expression].
+  ///
+  /// Returns whether a valid color was found and recorded.
+  bool _tryRecordColorValue(Expression expression, int? colorValue) {
+    if (colorValue == null) return false;
+
+    // Build color information from the Color value.
+    final color = _colorInformationForColorValue(colorValue);
+
+    // Record the color against the original entire expression.
+    _colors.add(ColorReference(expression.offset, expression.length, color));
+    return true;
+  }
+}
+
+/// Information about a color that is present in a document.
+class ColorInformation {
+  final int alpha;
+  final int red;
+  final int green;
+  final int blue;
+
+  ColorInformation(this.alpha, this.red, this.green, this.blue);
+}
+
+/// Information about a specific known location of a [ColorInformation]
+/// reference in a document.
+class ColorReference {
+  final int offset;
+  final int length;
+  final ColorInformation color;
+
+  ColorReference(this.offset, this.length, this.color);
+}
+
+class _ColorBuilder extends RecursiveAstVisitor<void> {
+  final ColorComputer computer;
+
+  _ColorBuilder(this.computer);
+
+  @override
+  void visitIndexExpression(IndexExpression node) {
+    // Colors.redAccent[500].
+    final index = node.index;
+    final indexValue = index is IntegerLiteral ? index.value : null;
+    if (indexValue != null) {
+      if (computer.tryAddColor(
+        node,
+        target: node.realTarget,
+        index: indexValue,
+      )) {
+        return;
+      }
+    }
+    super.visitIndexExpression(node);
+  }
+
+  @override
+  void visitInstanceCreationExpression(InstanceCreationExpression node) {
+    // Usually we return after finding a color, but constructors can
+    // have nested colors in their arguments so we walk all the way down.
+    if (!computer.tryAddColor(node)) {
+      // If we couldn't evaluate the constant, try the well-known color
+      // constructors for dart:ui/Flutter.
+      computer.tryAddKnownColorConstructor(node);
+    }
+
+    super.visitInstanceCreationExpression(node);
+  }
+
+  @override
+  void visitPrefixedIdentifier(PrefixedIdentifier node) {
+    // Try the whole node as a constant (eg. `MyThemeClass.staticField`).
+    if (computer.tryAddColor(node)) {
+      return;
+    }
+
+    // Try a field of a static, (eg. `const MyThemeClass().instanceField`).
+    if (computer.tryAddColor(
+      node,
+      target: node.prefix,
+      memberName: node.identifier.name,
+    )) {
+      return;
+    }
+
+    super.visitPrefixedIdentifier(node);
+  }
+
+  @override
+  void visitPropertyAccess(PropertyAccess node) {
+    // Handle things like CupterinoColors.activeBlue.darkColor where we can't
+    // evaluate the whole expression, but can evaluate CupterinoColors.activeBlue
+    // and read the darkColor.
+    if (computer.tryAddColor(
+      node,
+      target: node.realTarget,
+      memberName: node.propertyName.name,
+    )) {
+      return;
+    }
+
+    super.visitPropertyAccess(node);
+  }
+}
+
+extension _DartObjectExtensions on DartObject {
+  /// Reads the value of the field [field] from this object.
+  ///
+  /// If the field is not found, recurses up the super classes.
+  DartObject? getFieldFromHierarchy(String fieldName) =>
+      getField(fieldName) ??
+      getField(GenericState.SUPERCLASS_FIELD)?.getFieldFromHierarchy(fieldName);
+}

pkg/analysis_server/test/mock_packages/flutter/lib/cupertino.dart

@@ -0,0 +1,5 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export 'src/cupertino/colors.dart';

pkg/analysis_server/test/mock_packages/flutter/lib/material.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 export 'src/material/app_bar.dart';
+export 'src/material/colors.dart';
 export 'src/material/icons.dart';
 export 'src/material/scaffold.dart';
 export 'widgets.dart';

pkg/analysis_server/test/mock_packages/flutter/lib/painting.dart

@@ -5,6 +5,7 @@
 export 'src/painting/alignment.dart';
 export 'src/painting/basic_types.dart';
 export 'src/painting/box_decoration.dart';
+export 'src/painting/colors.dart';
 export 'src/painting/decoration.dart';
 export 'src/painting/edge_insets.dart';
 export 'src/painting/text_painter.dart';