Feature gql cli print schema (#258)

Author: leszekhanusz

docs/gql-cli/intro.rst

@@ -1,3 +1,5 @@
+.. _gql_cli:
+
 gql-cli
 =======
 
@@ -69,3 +71,10 @@ Then execute query from the file:
 
     $ cat query.gql | gql-cli wss://countries.trevorblades.com/graphql
     {"continent": {"name": "Africa"}}
+
+Print the GraphQL schema in a file
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: shell
+
+    $ gql-cli https://countries.trevorblades.com/graphql --print-schema > schema.graphql

docs/usage/validation.rst

@@ -21,6 +21,11 @@ The schema can be provided as a String (which is usually stored in a .graphql fi
 
     client = Client(schema=schema_str)
 
+.. note::
+    You can download a schema from a server by using :ref:`gql-cli <gql_cli>`
+
+    :code:`$ gql-cli https://SERVER_URL/graphql --print-schema > schema.graphql`
+
 OR can be created using python classes:
 
 .. code-block:: python

gql/cli.py

@@ -4,7 +4,7 @@
 from argparse import ArgumentParser, Namespace, RawDescriptionHelpFormatter
 from typing import Any, Dict
 
-from graphql import GraphQLError
+from graphql import GraphQLError, print_schema
 from yarl import URL
 
 from gql import Client, __version__, gql
@@ -38,6 +38,9 @@
 # Execute query saved in a file
 cat query.gql | gql-cli wss://countries.trevorblades.com/graphql
 
+# Print the schema of the backend
+gql-cli https://countries.trevorblades.com/graphql --print-schema
+
 """
 
 
@@ -92,6 +95,12 @@ def get_parser(with_examples: bool = False) -> ArgumentParser:
         help="set the operation_name value",
         dest="operation_name",
     )
+    parser.add_argument(
+        "--print-schema",
+        help="get the schema from instrospection and print it",
+        action="store_true",
+        dest="print_schema",
+    )
 
     return parser
 
@@ -241,7 +250,15 @@ async def main(args: Namespace) -> int:
     exit_code = 0
 
     # Connect to the backend and provide a session
-    async with Client(transport=transport) as session:
+    async with Client(
+        transport=transport, fetch_schema_from_transport=args.print_schema
+    ) as session:
+
+        if args.print_schema:
+            schema_str = print_schema(session.client.schema)
+            print(schema_str)
+
+            return exit_code
 
         while True:
 

tests/custom_scalars/test_money.py

@@ -410,19 +410,15 @@ async def handler(request):
         data = await request.json()
         source = data["query"]
 
-        print(f"data keys = {data.keys()}")
         try:
             variables = data["variables"]
-            print(f"variables = {variables!r}")
         except KeyError:
             variables = None
 
         result = graphql_sync(
             schema, source, variable_values=variables, root_value=root_value
         )
 
-        print(f"backend result = {result!r}")
-
         return web.json_response(
             {
                 "data": result.data,
@@ -742,3 +738,34 @@ def test_serialize_value_with_nullable_type():
     nullable_int = GraphQLInt
 
     assert serialize_value(nullable_int, None) is None
+
+
+@pytest.mark.asyncio
+async def test_gql_cli_print_schema(event_loop, aiohttp_server, capsys):
+
+    from gql.cli import get_parser, main
+
+    server = await make_money_backend(aiohttp_server)
+
+    url = str(server.make_url("/"))
+
+    parser = get_parser(with_examples=True)
+    args = parser.parse_args([url, "--print-schema"])
+
+    exit_code = await main(args)
+
+    assert exit_code == 0
+
+    # Check that the result has been printed on stdout
+    captured = capsys.readouterr()
+    captured_out = str(captured.out).strip()
+
+    print(captured_out)
+    assert (
+        """
+type Subscription {
+  spend(money: Money): Money
+}
+""".strip()
+        in captured_out
+    )