add error message as a comment on the logs

pkg/compiler/tool/status_files/update_from_log.dart

 // Copyright (c) 2017, 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.
 
 /// Script that updates dart2js status lines automatically for tests under the
 /// '$dart2js_with_kernel' configuration.
 ///
 /// This script is hardcoded to only support this configuration and relies on
 /// a convention for how the status files are structured, In particular,
 /// every status file for dart2js should have 2 sections:
@@ skipping 65 matching lines @@
     section.add(record);
     last = record;
   }
   section?.update();
 }
 
 /// Represents an existing entry in the logs.
 class ExistingEntry {
   final String test;
   final String status;
+  final bool hasComment;
 
-  ExistingEntry(this.test, this.status);
+  ExistingEntry(this.test, this.status, this.hasComment);
 
   static parse(String line) {
     var colonIndex = line.indexOf(':');
     var test = line.substring(0, colonIndex);
     var status = line.substring(colonIndex + 1).trim();
     var commentIndex = status.indexOf("#");
     if (commentIndex != -1) {
       status = status.substring(0, commentIndex);
     }
-    return new ExistingEntry(test, status);
+    return new ExistingEntry(test, status, commentIndex != -1);
   }
 }
 
 /// Represents a section in a .status file that corresponds to a specific suite
 /// and configuration.
 class ConfigurationInSuiteSection {
   final String suite;
   final String _statusFile;
   final String _contents;
   final int _begin;
@@ skipping 18 matching lines @@
     // same order: preserving entries that didn't change, and updating entries
     // where the logs show that the test status changed.
 
     // Records are already sorted, but we sort the file contents in case the
     // file has been tampered with.
     originalEntries.sort();
 
     var newContents = new StringBuffer();
     newContents.write(_contents.substring(0, _begin));
     addFromRecord(Record record) {
-      newContents.writeln('${record.test}: ${record.actual}');
+      var comment = record.reason != null ? ' # ${record.reason}' : '';
+      newContents.writeln('${record.test}: ${record.actual}$comment');
     }
 
     int i = 0, j = 0;
     while (i < originalEntries.length && j < _records.length) {
       var existingLine = originalEntries[i];
       if (existingLine.trim().isEmpty) {
         i++;
         continue;
       }
       var existing = ExistingEntry.parse(existingLine);
       var record = _records[j];
       var compare = existing.test.compareTo(record.test);
       if (compare < 0) {
         // Existing test was unaffected, copy the status line.
         newContents.writeln(existingLine);
         i++;
       } else if (compare > 0) {
         // New entry, if it's a failure, we haven't seen this before and must
         // add it. If the status says it is passing, we ignore it. We do this
         // to support making this script idempotent if the patching has already
         // been done.
         if (!record.isPassing) {
           // New failure never seen before
           addFromRecord(record);
           changes++;
         }
         j++;
       } else if (existing.status == record.actual) {
-        // This also should only happen if the patching has already been done.
-        // We don't complain to make this script idempotent.
-        newContents.writeln(existingLine);
+        if (!existing.hasComment && record.reason != null) {
+          addFromRecord(record);
+          changes++;
+        } else {
+          // This also should only happen if the patching has already been done.
+          // We don't complain to make this script idempotent.
+          newContents.writeln(existingLine);
+        }
         ignored++;
         i++;
         j++;
       } else {
         changes++;
         // The status changed, if it is now passing, we omit the entry entirely,
         // otherwise we use the status from the logs.
         if (!record.isPassing) {
           addFromRecord(record);
         }
@@ skipping 30 matching lines @@
       exit(1);
     }
     int begin = contents.indexOf('\n', sectionDeclaration) + 1;
     assert(begin != 0);
     int end = contents.indexOf('\n[', begin + 1);
     end = end == -1 ? contents.length : end + 1;
     return new ConfigurationInSuiteSection(
         suite, statusFile, contents, begin, end);
   }
 }