[tool] Dartfuzz use string matcher to output a diff

Before this CL the fuzzer would give a truncated output of stdout of both invocations on a divergence. This was not helpful for cases where the divergence is after the truncation. Instead, use package:matcher to report the diff between the strings. Bug: dart-lang#53972 Change-Id: I1eb1a5a35b5a5082fdacbca881498a61eb9cca1f Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/334440 Reviewed-by: Martin Kustermann <[email protected]> Commit-Queue: Daco Harkes <[email protected]>
nguyencse · Nov 7, 2023 · 7fdd032 · 7fdd032
1 parent dae322d
commit 7fdd032
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Showing 2 changed files with 13 additions and 10 deletions.
diff --git a/runtime/tools/dartfuzz/dartfuzz_test.dart b/runtime/tools/dartfuzz/dartfuzz_test.dart
@@ -7,6 +7,7 @@ import 'dart:isolate';
 import 'dart:math';
 
 import 'package:args/args.dart';
+import 'package:matcher/matcher.dart';
 
 import 'dartfuzz.dart';
 
@@ -464,9 +465,15 @@ class DartFuzzTest {
     }
   }
 
-  void printDivergenceOutput(String string, int numLines) {
-    final lines = string.split('\n');
-    print(lines.sublist(0, min(lines.length, numLines)).join('\n'));
+  void reportStringDifference(String a, String b) {
+    final matcher = equals(a);
+    final matches = matcher.matches(b, {});
+    if (matches) {
+      print('Strings are not different.');
+      return;
+    }
+    final mismatch = matcher.describeMismatch(b, StringDescription(), {}, true);
+    print(mismatch.toString());
   }
 
   void reportDivergence(TestResult result1, TestResult result2) {
@@ -475,13 +482,8 @@ class DartFuzzTest {
     print('\n$isolate: !DIVERGENCE! $version:$seed ($report)');
     if (result1.exitCode == result2.exitCode) {
       if (numOutputLines > 0) {
-        // Only report the actual output divergence details up to
-        // numOutputLines, since this output may be lengthy and should be
-        // reproducible anyway.
-        print('\nout1:\n');
-        printDivergenceOutput(result1.output, numOutputLines);
-        print('\nout2:\n');
-        printDivergenceOutput(result2.output, numOutputLines);
+        print('\nout1 and out2 are different:\n');
+        reportStringDifference(result1.output, result2.output);
       }
     } else {
       // For any other divergence, always report what went wrong.

diff --git a/runtime/tools/dartfuzz/pubspec.yaml b/runtime/tools/dartfuzz/pubspec.yaml
@@ -8,6 +8,7 @@ environment:
 dependencies:
   analyzer: any
   args: any
+  matcher: any
 
 dev_dependencies:
   lints: any