Add bisect config validation.

scripts/slave/recipe_modules/auto_bisect/config_validation.py

Index: scripts/slave/recipe_modules/auto_bisect/config_validation.py
diff --git a/scripts/slave/recipe_modules/auto_bisect/config_validation.py b/scripts/slave/recipe_modules/auto_bisect/config_validation.py
new file mode 100644
index 0000000000000000000000000000000000000000..1e4ecfb77318aef22303e0b75c6800457c2e36ee
--- /dev/null
+++ b/scripts/slave/recipe_modules/auto_bisect/config_validation.py
@@ -0,0 +1,110 @@
+# Copyright 2016 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.
+
+import re
+
+# Note: this module is tested by a unit test config_validation_test.py,
+# rather than recipe simulation tests.
+
+_BISECT_CONFIG_SCHEMA = {
+    'command': {'type': 'string', 'required': True},
+    'good_revision': {'type': 'revision', 'required': True},
+    'bad_revision': {'type': 'revision', 'required': True},
+    'bisect_bot': {'type': 'string'},
+    'metric': {'type': 'string'},
+    'bug_id': {'type': 'integer'},
+    'repeat_count': {'type': 'integer'},
+    'max_time_minutes': {'type': 'integer'},
+    'bisect_mode': {'type': 'string',
+                    'choices': ['mean', 'return_code', 'std_dev']},
+    'gs_bucket': {'type': 'string'},
+    'builder_host': {'type': 'string'},
+    'builder_port': {'type': 'integer'},
+    'test_type': {'type': 'string'},
+    'improvement_direction': {'type': 'integer'},
+    'recipe_tester_name': {'type': 'string'},
+    'try_job_id': {'type': 'integer'},
+}
+
+
+class ValidationFail(Exception):
+  """An exception class that represents a failure to validate."""
+
+
+def validate_bisect_config(config, schema=None):
+  """Checks the correctness of the given bisect job config."""
+  schema = _BISECT_CONFIG_SCHEMA if schema is None else schema
+  for key in set(schema):
+    validate_key(config, schema, key)
+
+  if 'good_revision' in schema and 'bad_revision' in schema:
+    _validate_revisions(config.get('good_revision'), config.get('bad_revision'))
+
+  if 'bisect_mode' in schema and 'metric' in schema:
+    _validate_metric(config.get('bisect_mode'), config.get('metric'))
+
+
+def validate_key(config, schema, key):  # pragma: no cover
+  """Checks the correctness of the given field in a config."""
+  if schema[key].get('required') and key not in config:
+    raise ValidationFail('Required key "%s" missing.' % key)
+  if key not in config:
+    return  # Optional field.
+  value = config[key]
+  field_type = schema[key].get('type')
+  if field_type == 'string':
+    _validate_string(value, key)
+  elif field_type == 'integer':
+    _validate_integer(value, key)
+  elif field_type == 'revision':
+    _validate_revision(value, key)
+  elif field_type == 'boolean':
+    _validate_boolean(value, key)
+  if 'choices' in schema[key] and value not in schema[key]['choices']:
+    _fail(value, key)
+
+
+def _fail(value, key):
+  raise ValidationFail('Invalid value %r for "%s".' % (value, key))
+
+
+def _validate_string(value, key):  # pragma: no cover
+  if not isinstance(value, basestring):
+    _fail(value, key)
+
+
+def _validate_revision(value, key):  # pragma: no cover
+  s = str(value)
+  if not (s.isdigit() or re.match('^[0-9A-Fa-f]{40}$', s)):
+    _fail(value, key)
+
+
+def _validate_integer(value, key):  # pragma: no cover
+  try:
+    int(value)
+  except ValueError:
+    _fail(value, key)
+
+
+def _validate_boolean(value, key):  # pragma: no cover
+  if value not in (True, False):
+    _fail(value, key)
+
+
+def _validate_revisions(good_revision, bad_revision):  # pragma: no cover
+  try:
+    earlier = int(good_revision)
+    later = int(bad_revision)
+  except ValueError:
+    return  # The revisions could be sha1 hashes.
+  if earlier >= later:
+    raise ValidationFail('Order of good_revision (%d) and bad_revision(%d) '
+                         'is reversed.' % (earlier, later))
+
+
+def _validate_metric(bisect_mode, metric):  # pragma: no cover
+  if bisect_mode not in ('mean', 'std_dev'):
+    return
+  if not (isinstance(metric, basestring) and metric.count('/') == 1):
+    raise ValidationFail('Invalid value for "metric": %s' % metric)