Add configurable deckhand render validation

Currently deckhand render validation is disabled by default with no
option to override that behavior from the command line.  Resolve this
by:
1. Adding CLI render flag 'validate', default=True
2. Updating CLI documentation
3. Update pegleg.engine.site.render method to include configurable
   validate flag
4. Update pegleg.engine.util.deckhand.deckhand_render method to
   validate=True by default (previously False)
5. Update pegleg.engine.util.deckhand.deckhand_render method to
   perform deckhand's validate all function on rendered documents

NOTE: Validation logic is handled in deckhand, see
https://opendev.org/airship/deckhand/src/branch/master/deckhand/engine/layering.py
https://opendev.org/airship/deckhand/src/branch/master/deckhand/engine/document_validation.py

Change-Id: I042fad4b2bf08c88e3a2eef6a54dede5d45c28f5

doc/source/cli/cli.rst

@@ -337,6 +337,12 @@ Name of site.
 
 Where to output.
 
+**-v/--validate** (Optional). Default is True.
+
+Whether to pre-validate documents using built-in schema validation.
+Skips over externally registered DataSchema documents to avoid
+false positives.
+
 ::
 
   ./pegleg <command> <options> render site_name

pegleg/cli.py

@@ -313,9 +313,19 @@ def show(*, output_stream, site_name):
     default=sys.stdout,
     show_default=True,
     help='Where to output.')
+@click.option(
+    '-v',
+    '--validate',
+    'validate',
+    is_flag=True,
+    default=True,
+    show_default=True,
+    help='Whether to pre-validate documents using built-in schema validation. '
+         'Skips over externally registered DataSchema documents to avoid '
+         'false positives.')
 @SITE_REPOSITORY_ARGUMENT
-def render(*, output_stream, site_name):
-    engine.site.render(site_name, output_stream)
+def render(*, output_stream, site_name, validate):
+    engine.site.render(site_name, output_stream, validate)
 
 
 @site.command('lint', help='Lint a given site in a repository')

pegleg/engine/site.py

@@ -83,14 +83,14 @@ def collect(site_name, save_location):
         _collect_to_stdout(site_name)
 
 
-def render(site_name, output_stream):
+def render(site_name, output_stream, validate):
     documents = []
     for filename in util.definition.site_files(site_name):
         with open(filename) as f:
             documents.extend(list(yaml.safe_load_all(f)))
 
     rendered_documents, errors = util.deckhand.deckhand_render(
-        documents=documents)
+        documents=documents, validate=validate)
     err_msg = ''
     if errors:
         for err in errors:

pegleg/engine/util/deckhand.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from deckhand.engine import document_validation
 from deckhand.engine import layering
 from deckhand import errors as dh_errors
 
@@ -43,7 +44,7 @@ def load_schemas_from_docs(documents):
 
 def deckhand_render(documents=None,
                     fail_on_missing_sub_src=False,
-                    validate=False):
+                    validate=True):
     documents = documents or []
     errors = []
     rendered_documents = []
@@ -57,6 +58,17 @@ def deckhand_render(documents=None,
             fail_on_missing_sub_src=fail_on_missing_sub_src,
             validate=validate)
         rendered_documents = [dict(d) for d in deckhand_eng.render()]
+        if validate:
+            validator = document_validation.DocumentValidation(
+                rendered_documents)
+            results = validator.validate_all()
+            for result in results:
+                if result['errors']:
+                    errors.append(
+                        (DECKHAND_RENDER_EXCEPTION,
+                         'During rendering Deckhand was unable to validate '
+                         'the following document, details: %s.' % (
+                             result['errors'])))
     except dh_errors.DeckhandException as e:
         errors.append(
             (DECKHAND_RENDER_EXCEPTION,