Issue 52543. Support for 'remove comparison' fix for IfElement.

Bug: #52543
Change-Id: Ibeecc42db2135d507ed8f74f5a4888fb122b131f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/306312
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/services/correction/dart/remove_comparison.dart

@@ -79,13 +79,42 @@ class RemoveComparison extends CorrectionProducer {
           (type == TokenType.BAR_BAR && _conditionIsFalse)) {
         await _removeOperatorAndOperand(builder, parent);
       }
+    } else if (parent is IfElement) {
+      await _ifElement(parent, builder);
     } else if (parent is IfStatement) {
       if (parent.elseStatement == null && _conditionIsTrue) {
         await _ifStatement(parent, builder);
       }
     }
   }
 
+  Future<void> _ifElement(IfElement node, ChangeBuilder builder) async {
+    if (_conditionIsTrue) {
+      await builder.addDartFileEdit(file, (builder) {
+        final text = _textWithLeadingComments(node.thenElement);
+        final unIndented = utils.indentLeft(text);
+        builder.addSimpleReplacement(range.node(node), unIndented);
+      });
+    } else if (_conditionIsFalse) {
+      final elseElement = node.elseElement;
+      if (elseElement != null) {
+        await builder.addDartFileEdit(file, (builder) {
+          final text = _textWithLeadingComments(elseElement);
+          final unIndented = utils.indentLeft(text);
+          builder.addSimpleReplacement(range.node(node), unIndented);
+        });
+      } else {
+        final elements = node.parent.containerElements;
+        if (elements != null) {
+          await builder.addDartFileEdit(file, (builder) {
+            final nodeRange = range.nodeInList(elements, node);
+            builder.addDeletion(nodeRange);
+          });
+        }
+      }
+    }
+  }
+
   Future<void> _ifStatement(IfStatement node, ChangeBuilder builder) async {
     await builder.addDartFileEdit(file, (builder) {
       var nodeRange = utils.getLinesRangeStatements([node]);
@@ -127,4 +156,20 @@ class RemoveComparison extends CorrectionProducer {
       builder.addDeletion(operatorAndOperand);
     });
   }
+
+  String _textWithLeadingComments(AstNode node) {
+    return utils.getNodeText(node, withLeadingComments: true);
+  }
+}
+
+extension on AstNode? {
+  NodeList<AstNode>? get containerElements {
+    final self = this;
+    if (self is ListLiteral) {
+      return self.elements;
+    } else if (self is SetOrMapLiteral) {
+      return self.elements;
+    }
+    return null;
+  }
 }

pkg/analysis_server/lib/src/services/correction/util.dart

@@ -876,8 +876,17 @@ class CorrectionUtils {
   }
 
   /// Returns the text of the given [AstNode] in the unit.
-  String getNodeText(AstNode node) {
-    return getText(node.offset, node.length);
+  String getNodeText(
+    AstNode node, {
+    bool withLeadingComments = false,
+  }) {
+    final firstToken = withLeadingComments
+        ? node.beginToken.precedingComments ?? node.beginToken
+        : node.beginToken;
+    final offset = firstToken.offset;
+    final end = node.endToken.end;
+    final length = end - offset;
+    return getText(offset, length);
   }
 
   /// Returns the line prefix consisting of spaces and tabs on the left from the
@@ -975,6 +984,28 @@ class CorrectionUtils {
     throw UnimplementedError('(${type.runtimeType}) $type');
   }
 
+  /// Splits [text] into lines, and removes one level of indent from each line.
+  /// Lines that don't start with indentation are left as is.
+  String indentLeft(String text) {
+    final buffer = StringBuffer();
+    final indent = getIndent(1);
+    final eol = endOfLine;
+    final lines = text.split(eol);
+    for (final line in lines) {
+      if (buffer.isNotEmpty) {
+        buffer.write(eol);
+      }
+      final String updatedLine;
+      if (line.startsWith(indent)) {
+        updatedLine = line.substring(indent.length);
+      } else {
+        updatedLine = line;
+      }
+      buffer.write(updatedLine);
+    }
+    return buffer.toString();
+  }
+
   /// Indents given source left or right.
   String indentSourceLeftRight(String source, {bool indentLeft = true}) {
     var sb = StringBuffer();

pkg/analysis_server/test/src/services/correction/fix/remove_comparison_test.dart

@@ -150,6 +150,189 @@ void f(String s) {
 ''');
   }
 
+  Future<void> test_ifElement_alwaysFalse_hasElse() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    if (x == null) 1 else -1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    -1,
+    2,
+  ];
+}
+''');
+  }
+
+  Future<void> test_ifElement_alwaysFalse_hasElse_withComments() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    // C1
+    if (x == null)
+      // C2
+      1
+    else
+      // C3
+      -1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    // C1
+    // C3
+    -1,
+    2,
+  ];
+}
+''');
+  }
+
+  Future<void> test_ifElement_alwaysFalse_noElse_insideList() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    if (x == null) 1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    2,
+  ];
+}
+''');
+  }
+
+  Future<void>
+      test_ifElement_alwaysFalse_noElse_insideList_withComments() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    // C1
+    if (x == null)
+      // C2
+      1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    2,
+  ];
+}
+''');
+  }
+
+  Future<void> test_ifElement_alwaysFalse_noElse_insideSet() async {
+    await resolveTestCode('''
+Object f(int x) {
+  return {
+    0,
+    if (x == null) 1,
+    2,
+  };
+}
+''');
+    await assertHasFix('''
+Object f(int x) {
+  return {
+    0,
+    2,
+  };
+}
+''');
+  }
+
+  Future<void> test_ifElement_alwaysTrue() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    if (x != null)
+      1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    1,
+    2,
+  ];
+}
+''');
+  }
+
+  Future<void> test_ifElement_alwaysTrue_hasElse() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    if (x != null) 1 else -1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    1,
+    2,
+  ];
+}
+''');
+  }
+
+  Future<void> test_ifElement_alwaysTrue_withComments() async {
+    await resolveTestCode('''
+void f(int x) {
+  [
+    0,
+    // C1
+    if (x != null)
+      // C2
+      1,
+    2,
+  ];
+}
+''');
+    await assertHasFix('''
+void f(int x) {
+  [
+    0,
+    // C1
+    // C2
+    1,
+    2,
+  ];
+}
+''');
+  }
+
   Future<void> test_ifStatement_thenBlock() async {
     await resolveTestCode('''
 void f(String s) {