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..4816cb19495747bc68b99fcf8f7180eee15443fd
--- /dev/null
+++ b/scripts/slave/recipe_modules/auto_bisect/config_validation.py
@@ -0,0 +1,84 @@
+# 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
+
+_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'},
+    'truncate_percent': {'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'},

[qyearsley, 2016/03/11 01:41:34]

Anything else that should be added? Or anything that should be removed?

[RobertoCN, 2016/03/14 01:26:23]

Metric could be required if the bisect_mode is mean or std_dev.
Truncate percent is mostly deprecated, right? (except for clank)

[qyearsley, 2016/03/18 22:50:19]

Check for metric added; truncate_percent removed from the default config schema.

+}
+
+
+class ValidationFail(Exception):
+  """An exception class that represents a failure to validate."""
+
+
+def validate_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)

[qyearsley, 2016/03/11 01:41:34]

Potentially to be added: check revision order and distance. This could also be
done after expanding the revision range.

[RobertoCN, 2016/03/14 01:26:23]

could also check for well-formedness of gs location and url, and also metric.

[qyearsley, 2016/03/18 22:50:19]

In most bisect configs, there aren't any gs URLs, but there is a gs bucket.

Example:
https://build.chromium.org/p/tryserver.chromium.perf/builders/linux_perf_bise...

Checking for revision order and metric well-formedness added.

+
+
+def validate_key(config, schema, key):
+  """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):
+  if not isinstance(value, basestring):
+    _fail(value, key)
+
+
+def _validate_revision(value, key):
+  s = str(value)
+  if not (s.isdigit() or re.match('^[0-9A-Fa-f]{40}$', s)):
+    _fail(value, key)
+
+
+def _validate_integer(value, key):
+  try:
+    int(value)
+  except ValueError:
+    _fail(value, key)
+
+
+def _validate_boolean(value, key):
+  if value not in (True, False):
+    _fail(value, key)