Collect UMA statistics on which chrome://flags lead to chrome restart on ChromeOS.

tools/about_flags_switches_histogram_ids_checker/about_flags_switches_histogram_ids_checker.py

Index: tools/about_flags_switches_histogram_ids_checker/about_flags_switches_histogram_ids_checker.py
diff --git a/tools/about_flags_switches_histogram_ids_checker/about_flags_switches_histogram_ids_checker.py b/tools/about_flags_switches_histogram_ids_checker/about_flags_switches_histogram_ids_checker.py
new file mode 100644
index 0000000000000000000000000000000000000000..f69800073aa8c0d2854d4f41c5cb56a0fd5c936b
--- /dev/null
+++ b/tools/about_flags_switches_histogram_ids_checker/about_flags_switches_histogram_ids_checker.py
@@ -0,0 +1,164 @@
+# Copyright 2014 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.
+
+class AboutFlagsSwitchesHistogramIDsChecker(object):
+  """Verify that changes to SwitchesUmaHistogramIds enum are valid.
+
+  This class is used to check SwitchesUmaHistogramIds enum is never shrinked or
+  reordered. This enum is used to report UMA histograms, so IDs must never
+  change. See comments on the top of
+  chrome/browser/about_flags_switches_histogram_ids.h .
+
+  """
+  def __init__(self, input_api, output_api, path):
+    self.input_api = input_api
+    self.output_api = output_api
+    self.path = path
+    self.warnings_exist = False
+    self.enum_found = False
+    self.results = []
+
+  def LogInfo(self, message):
+    self.input_api.logging.info(message)
+    return
+
+  def LogDebug(self, message):
+    self.input_api.logging.debug(message)
+    return
+
+  def GetLongMessage(self, local_path):
+    return str("The file \"%s\"\n"
+               "contains the definition of the 'SwitchesUmaHistogramId' enum,\n"
+               "which should be edited in specific ways only.\n"
+               "*** read the comments at the top of the header file ***."
+               % (local_path))
+
+  def EmitWarning(self, message, line_number=None, line_text=None):
+    """Emits a presubmit prompt warning containing the short message
+    |message|. |item| is |LOCAL_PATH| with optional |line_number| and
+    |line_text|.
+
+    """
+    if line_number is not None and line_text is not None:
+      item = "%s(%d): %s" % (self.path, line_number, line_text)
+    elif line_number is not None:
+      item = "%s(%d)" % (self.path, line_number)
+    else:
+      item = self.path
+    if self.warnings_exist :
+      long_message = ''
+    else :
+      long_message = self.GetLongMessage(self.path)
+    self.warnings_exist = True
+
+    self.LogInfo(message)
+    self.results.append(
+      self.output_api.PresubmitPromptWarning(message, [item], long_message))
+
+  def ReportDeletedLines(self, expected_new_deprecated, prefix=''):
+    message = prefix
+    message += str("It looks like you are deleting line(s) from the "
+                  "enum definition. This should never happen.\n")
+    message += "The following line(s) have been deleted:\n"
+    for value in expected_new_deprecated :
+      message += "\t" + value + "\n"
+    message += str("Remember to add 'DEPRECATED_' prefix to the no more "
+                   "needed entries")
+    self.EmitWarning(message)
+
+  def VerifyNewItemname(self, item) :
+    m = self.input_api.re.match(r"^UMA_HISTOGRAM_ID_", item)
+    if not m :
+      self.EmitWarning("New enum item '" + item + "' doesn't start with " +
+                       "'UMA_HISTOGRAM_ID_'.")
+      return False
+    return True
+
+  def CheckDiff(self, affected_file):
+    """Check diff is valid.
+
+    """
+    expected_new_deprecated = []
+    result = True
+    end_flag = False # End of enum found (only addition is allowed).
+    for line in affected_file.GenerateScmDiff().splitlines():
+      m = self.input_api.re.match(
+        r"^([+ -])  *([A-Za-z0-9_]+) *,", line)
+      if not m :
+        # Check the last line (probably without ',').
+        if not self.enum_found :
+          continue
+        m = self.input_api.re.match(
+          r"^([+ -])  *([A-Za-z0-9_]+)", line)
+      if m :
+        self.enum_found = True
+        self.LogDebug("MATCHED '" + line + "'")
+        if end_flag :
+          # We are at the end of enum.
+          # Only new items are allowed here.
+          if m.group(1) == "+" :
+            if not self.VerifyNewItemname(m.group(2)) :
+              result = False
+            continue
+          result = False
+          message = str("It looks like you are inserting lines in the "
+                        "middle of the enum definition. This should never "
+                        "happen.\n")
+          if m.group(1) == "-" :
+            message += str("Found deleted item '" + m.group(2) +
+                           "' after some new lines added.")
+          elif m.group(1) == " " :
+            message += str("A new lines have been added before item '" +
+                           m.group(2) + "'.")
+          else :
+            raise Exception("Unknown SCM diff op '" + m.group(1) +
+                            "' found in diff line '" + line + "'")
+          self.EmitWarning(message)
+        else : # end_flag is False
+          if m.group(1) == "-" :
+            expected_new_deprecated.append(m.group(2))
+            continue
+
+          # All items must be renamed before any unchanged line.
+          if m.group(1) == " " and len(expected_new_deprecated) == 0 :
+            continue
+
+          if m.group(1) == "+" :
+            if len(expected_new_deprecated) :
+              if "DEPRECATED_" + expected_new_deprecated[0] == m.group(2) :
+                  expected_new_deprecated.pop(0)
+                  continue;
+            else :
+              if not self.VerifyNewItemname(m.group(2)) :
+                result = False
+              # New lines must be added to the end, so we've reached enum end.
+              end_flag = True;
+              continue;
+
+        # Format error:
+        result = False
+        if len(expected_new_deprecated) :
+          self.ReportDeletedLines(expected_new_deprecated,
+              str("The unexpected line adds new value '" + m.group(2) +
+                  "', but 'DEPRECATED_" + expected_new_deprecated[0] +
+                  "' is expected.\n"))
+          expected_new_deprecated = []
+        continue
+
+    if len(expected_new_deprecated) :
+      self.ReportDeletedLines(expected_new_deprecated)
+
+    return result
+
+  def PerformChecks(self, affected_file):
+    if not self.CheckDiff(affected_file):
+      return
+
+  def Run(self):
+    for file in self.input_api.AffectedFiles(include_deletes=True):
+      if file.LocalPath() == self.path:
+        self.LogInfo("Start processing file.")
+        self.PerformChecks(file)
+        self.LogInfo("Done processing file.")
+    return self.results

[Ilya Sherman, 2014/07/21 22:12:59]

Can you reuse some of the existing code, rather than just forking it?

[Alexander Alekseev, 2014/07/22 14:25:06]

Hmm. That means splitting strict_enum_value_checker.py (and *_test.py) into an
environment library and actual checkers. I'll look into it, but doesn't it seem
too much for all this?