Add --file option to generateschema

docs/api-guide/schemas.md

@@ -30,7 +30,7 @@ into the commonly used YAML-based OpenAPI format.
 If your schema is static, you can use the `generateschema` management command:
 
 ```bash
-./manage.py generateschema > openapi-schema.yml
+./manage.py generateschema --file openapi-schema.yml
 ```
 
 Once you've generated a schema in this way you can annotate it with any

rest_framework/management/commands/generateschema.py

@@ -25,6 +25,7 @@ def add_arguments(self, parser):
             parser.add_argument('--format', dest="format", choices=['openapi', 'openapi-json'], default='openapi', type=str)
         parser.add_argument('--urlconf', dest="urlconf", default=None, type=str)
         parser.add_argument('--generator_class', dest="generator_class", default=None, type=str)
+        parser.add_argument('--file', dest="file", default=None, type=str)
 
     def handle(self, *args, **options):
         if options['generator_class']:
@@ -40,7 +41,12 @@ def handle(self, *args, **options):
         schema = generator.get_schema(request=None, public=True)
         renderer = self.get_renderer(options['format'])
         output = renderer.render(schema, renderer_context={})
-        self.stdout.write(output.decode())
+
+        if options['file']:
+            with open(options['file'], 'wb') as f:
+                f.write(output)
+        else:
+            self.stdout.write(output.decode())
 
     def get_renderer(self, format):
         if self.get_mode() == COREAPI_MODE:

tests/schemas/test_managementcommand.py

@@ -1,4 +1,6 @@
 import io
+import os
+import tempfile
 
 import pytest
 from django.conf.urls import url
@@ -73,6 +75,21 @@ def test_accepts_custom_schema_generator(self):
         out_json = yaml.safe_load(self.out.getvalue())
         assert out_json == CustomSchemaGenerator.SCHEMA
 
+    def test_writes_schema_to_file_on_parameter(self):
+        fd, path = tempfile.mkstemp()
+        try:
+            call_command('generateschema', '--file={}'.format(path), stdout=self.out)
+            # nothing on stdout
+            assert not self.out.getvalue()
+
+            call_command('generateschema', stdout=self.out)
+            expected_out = self.out.getvalue()
+            # file output identical to stdout output
+            with os.fdopen(fd) as fh:
+                assert expected_out and fh.read() == expected_out
+        finally:
+            os.remove(path)
+
     @pytest.mark.skipif(yaml is None, reason='PyYAML is required.')
     @override_settings(REST_FRAMEWORK={'DEFAULT_SCHEMA_CLASS': 'rest_framework.schemas.AutoSchema'})
     def test_coreapi_renders_default_schema_with_custom_title_url_and_description(self):