From ccf5d641c5c4cf8817010d295a42917a424ec04b Mon Sep 17 00:00:00 2001
From: Dan Field <dnfield@google.com>
Date: Tue, 4 Feb 2020 14:23:03 -0800
Subject: [PATCH] Fix stack filtering (#49956)

---
 .../lib/src/foundation/assertions.dart        |  5 ++++-
 .../test/foundation/assertions_test.dart      | 20 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/foundation/assertions.dart b/packages/flutter/lib/src/foundation/assertions.dart
index cb55da20f6..3e9c676446 100644
--- a/packages/flutter/lib/src/foundation/assertions.dart
+++ b/packages/flutter/lib/src/foundation/assertions.dart
@@ -126,7 +126,7 @@ class RepetitiveStackFrameFilter extends StackFilter {
 
   @override
   void filter(List<StackFrame> stackFrames, List<String> reasons) {
-    for (int index = 0; index < stackFrames.length; index += 1) {
+    for (int index = 0; index < stackFrames.length - numFrames; index += 1) {
       if (_matchesFrames(stackFrames.skip(index).take(numFrames).toList())) {
         reasons.setRange(index, index + numFrames, _replacements);
         index += numFrames - 1;
@@ -135,6 +135,9 @@ class RepetitiveStackFrameFilter extends StackFilter {
   }
 
   bool _matchesFrames(List<StackFrame> stackFrames) {
+    if (stackFrames.length < numFrames) {
+      return false;
+    }
     for (int index = 0; index < stackFrames.length; index++) {
       if (!frames[index].matches(stackFrames[index])) {
         return false;
diff --git a/packages/flutter/test/foundation/assertions_test.dart b/packages/flutter/test/foundation/assertions_test.dart
index 05b7272138..e0780fffb6 100644
--- a/packages/flutter/test/foundation/assertions_test.dart
+++ b/packages/flutter/test/foundation/assertions_test.dart
@@ -428,4 +428,24 @@ void main() {
     expect(trace, isNotNull);
     expect(trace.value, stack);
   });
+
+  test('RepetitiveStackFrameFilter does not go out of range', () {
+    const RepetitiveStackFrameFilter filter = RepetitiveStackFrameFilter(
+      frames: <PartialStackFrame>[
+        PartialStackFrame(className: 'TestClass', method: 'test1', package: 'package:test/blah.dart'),
+        PartialStackFrame(className: 'TestClass', method: 'test2', package: 'package:test/blah.dart'),
+        PartialStackFrame(className: 'TestClass', method: 'test3', package: 'package:test/blah.dart'),
+      ],
+      replacement: 'test',
+    );
+    final List<String> reasons = List<String>(2);
+    filter.filter(
+      const <StackFrame>[
+        StackFrame(className: 'TestClass', method: 'test1', packageScheme: 'package', package: 'test', packagePath: 'blah.dart', line: 1, column: 1, number: 0, source: ''),
+        StackFrame(className: 'TestClass', method: 'test2', packageScheme: 'package', package: 'test', packagePath: 'blah.dart', line: 1, column: 1, number: 0, source: ''),
+      ],
+      reasons,
+    );
+    expect(reasons, List<String>(2));
+  });
 }