feat: tool to print diff between netplan and networkv2 schema (#5200)

Netplan contains many keys that do not exist in the cloud-init
networkv2 schema. This change adds a tools script to print the
difference between netplan's examples (since they do not have a
schema as such) and the cloud-init networkv2 schema.

tools/netplan_schema_check.py

@@ -0,0 +1,91 @@
+import argparse
+import os
+import yaml
+
+from jsonschema import Draft4Validator
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(
+        description="""
+This script validates netplan example files against the cloud-init networkv2
+schema.  The goal is to provide an easy way to track drift between networkv2
+and netplan.
+
+Netplan does not provide a centralized schema file to compare against directly,
+but does maintain a reasonably comprehensive examples directory.  This script
+relies on that directory to glean the netplan schema.
+            """,
+        formatter_class=argparse.RawTextHelpFormatter,
+    )
+    parser.add_argument(
+        "--schema-file",
+        required=True,
+        help="""
+The cloud-init networkv2 schema file found in
+cloudinit/config/schemas/schema-network-config-v2.json
+in this repository.
+        """,
+    )
+    parser.add_argument(
+        "--netplan-examples",
+        required=True,
+        help="""
+The examples/ directory in the netplan repo.  The most
+recent netplan repo can be cloned from
+https://github.com/canonical/netplan.
+        """,
+    )
+    return parser.parse_args()
+
+
+def validate_netplan_against_networkv2(schema_file, netplan_examples):
+    """
+    This script validates netplan example files against the cloud-init
+    networkv2 schema.  The goal is to provide an easy way to track drift
+    between networkv2 and netplan.
+
+    Netplan does not provide a centralized schema file to compare against
+    directly, but does maintain a reasonably comprehensive examples directory.
+    This script relies on that directory to glean the netplan schema.
+
+    There are two arguments required for this script.  The first is schema_file
+    which should point to the cloud-init networkv2 schema file found in
+    cloudinit/config/schemas/schema-network-config-v2.json in this repository.
+    The second is netplan_examples which should point to the examples/
+    directory in the netplan repo.  The most recent netplan repo can be cloned
+    from https://github.com/canonical/netplan.
+    """
+    networkv2_schema = None
+    with open(schema_file) as f:
+        networkv2_schema = yaml.safe_load(f)
+    validator = Draft4Validator(networkv2_schema)
+
+    error_obj = {}
+    for walk_tuple in os.walk(netplan_examples):
+        filenames = walk_tuple[2]
+        for fname in filenames:
+            if fname.endswith(".yaml"):
+                with open(netplan_examples + fname) as netplan_f:
+                    netplan_example = yaml.safe_load(netplan_f)
+                    errors = validator.iter_errors(netplan_example)
+                    for e in errors:
+                        schema_path_str = "-".join(map(str, e.schema_path))
+                        if schema_path_str not in error_obj:
+                            error_obj[schema_path_str] = {}
+                        if e.message not in error_obj[schema_path_str]:
+                            error_obj[schema_path_str][e.message] = set()
+                        error_obj[schema_path_str][e.message].add(fname)
+
+    # clean up error_obj for human readability
+    for schema_path in error_obj:
+        for message in error_obj[schema_path]:
+            error_obj[schema_path][message] = list(
+                error_obj[schema_path][message]
+            )
+    print(yaml.dump(error_obj))
+
+
+if __name__ == "__main__":
+    args = parse_args()
+    validate_netplan_against_networkv2(args.schema_file, args.netplan_examples)