Add Strict Metaschema Validation (#1101)

Improve schema validation.

This adds strict validation of config module definitions at testing
time, with plumbing included for future runtime validation. This
eliminates a class of bugs resulting from schemas that have definitions
that are incorrect, but get interpreted by jsonschema as
"additionalProperties" that are therefore ignored.

- Add strict meta-schema for jsonschema unit test validation
- Separate schema from module metadata structure
- Improve type annotations for various functions and data types

Cleanup:
- Remove unused jsonschema "required" elements 
- Eliminate manual memoization in schema.py:get_schema(),
        reference module.__doc__ directly

1 files changed, 7 insertions, 4 deletions

diff --git a/cloudinit/config/cc_chef.py b/cloudinit/config/cc_chef.py
index 7b20222e..ed734d1c 100644
--- a/cloudinit/config/cc_chef.py
+++ b/cloudinit/config/cc_chef.py
@@ -14,8 +14,7 @@ import os
 from textwrap import dedent
 
 from cloudinit import subp
-from cloudinit.config.schema import (
-    get_schema_doc, validate_cloudconfig_schema)
+from cloudinit.config.schema import get_meta_doc, validate_cloudconfig_schema
 from cloudinit import templater
 from cloudinit import temp_utils
 from cloudinit import url_helper
@@ -89,7 +88,8 @@ CHEF_EXEC_DEF_ARGS = tuple(['-d', '-i', '1800', '-s', '20'])
 
 frequency = PER_ALWAYS
 distros = ["all"]
-schema = {
+
+meta = {
     'id': 'cc_chef',
     'name': 'Chef',
     'title': 'module that configures, starts and installs chef',
@@ -126,6 +126,9 @@ schema = {
           ssl_verify_mode: :verify_peer
           validation_name: yourorg-validator""")],
     'frequency': frequency,
+}
+
+schema = {
     'type': 'object',
     'properties': {
         'chef': {
@@ -357,7 +360,7 @@ schema = {
     }
 }
 
-__doc__ = get_schema_doc(schema)
+__doc__ = get_meta_doc(meta, schema)
 
 
 def post_run_chef(chef_cfg, log):