Increase OAS description

Parce docstring of http handlers to increase OAS
Remove the not expected definitions key in the OAS

aiohttp_pydantic/oas/cmd.py

@@ -1,10 +1,28 @@
 import argparse
 import importlib
 import json
-
+from typing import Dict, Protocol, Optional, Callable
+import sys
 from .view import generate_oas
 
 
+class YamlModule(Protocol):
+    """
+    Yaml Module type hint
+    """
+
+    def dump(self, data) -> str:
+        pass
+
+
+yaml: Optional[YamlModule]
+
+try:
+    import yaml
+except ImportError:
+    yaml = None
+
+
 def application_type(value):
     """
     Return aiohttp application defined in the value.
@@ -26,6 +44,35 @@ def application_type(value):
         raise argparse.ArgumentTypeError(error) from error
 
 
+def base_oas_file_type(value) -> Dict:
+    """
+    Load base oas file
+    """
+    try:
+        with open(value) as oas_file:
+            data = oas_file.read()
+    except OSError as error:
+        raise argparse.ArgumentTypeError(error) from error
+
+    return json.loads(data)
+
+
+def format_type(value) -> Callable:
+    """
+    Date Dumper one of (json, yaml)
+    """
+    dumpers = {"json": lambda data: json.dumps(data, sort_keys=True, indent=4)}
+    if yaml is not None:
+        dumpers["yaml"] = yaml.dump
+
+    try:
+        return dumpers[value]
+    except KeyError:
+        raise argparse.ArgumentTypeError(
+            f"Wrong format value. (allowed values: {tuple(dumpers.keys())})"
+        ) from None
+
+
 def setup(parser: argparse.ArgumentParser):
     parser.add_argument(
         "apps",
@@ -35,11 +82,52 @@ def setup(parser: argparse.ArgumentParser):
         help="The name of the module containing the asyncio.web.Application."
         " By default the variable named 'app' is loaded but you can define"
         " an other variable name ending the name of module with : characters"
-        " and the name of variable. Example: my_package.my_module:my_app",
+        " and the name of variable. Example: my_package.my_module:my_app"
+        " If your asyncio.web.Application is returned by a function, you can"
+        " use the syntax: my_package.my_module:my_app()",
+    )
+    parser.add_argument(
+        "-b",
+        "--base-oas-file",
+        metavar="FILE",
+        dest="base",
+        type=base_oas_file_type,
+        help="A file that will be used as base to generate OAS",
+        default={},
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        metavar="FILE",
+        type=argparse.FileType("w"),
+        help="File to write the output",
+        default=sys.stdout,
+    )
+
+    if yaml:
+        help_output_format = (
+            "The output format, can be 'json' or 'yaml' (default is json)"
+        )
+    else:
+        help_output_format = "The output format, only 'json' is available install pyyaml to have yaml output format"
+
+    parser.add_argument(
+        "-f",
+        "--format",
+        metavar="FORMAT",
+        dest="formatter",
+        type=format_type,
+        help=help_output_format,
+        default=format_type("json"),
     )
 
     parser.set_defaults(func=show_oas)
 
 
 def show_oas(args: argparse.Namespace):
-    print(json.dumps(generate_oas(args.apps), sort_keys=True, indent=4))
+    """
+    Display Open API Specification on the stdout.
+    """
+    spec = args.base
+    spec.update(generate_oas(args.apps))
+    print(args.formatter(spec), file=args.output)