call_with_supported_arguments() util, refs #581

datasette/utils/__init__.py

@@ -3,6 +3,7 @@ from collections import OrderedDict
 import base64
 import click
 import hashlib
+import inspect
 import json
 import mergedeep
 import os
@@ -803,3 +804,13 @@ def parse_metadata(content):
             return yaml.safe_load(content)
         except yaml.YAMLError:
             raise BadMetadataError("Metadata is not valid JSON or YAML")
+
+
+def call_with_supported_arguments(fn, **kwargs):
+    parameters = inspect.signature(fn).parameters.keys()
+    call_with = []
+    for parameter in parameters:
+        if parameter not in kwargs:
+            raise TypeError("{} requires parameters {}".format(fn, tuple(parameters)))
+        call_with.append(kwargs[parameter])
+    return fn(*call_with)

tests/test_utils.py

@@ -446,3 +446,14 @@ async def test_request_post_vars():
 
     request = Request(scope, receive)
     assert {"foo": "bar", "baz": "1"} == await request.post_vars()
+
+
+def test_call_with_supported_arguments():
+    def foo(a, b):
+        return "{}+{}".format(a, b)
+
+    assert "1+2" == utils.call_with_supported_arguments(foo, a=1, b=2)
+    assert "1+2" == utils.call_with_supported_arguments(foo, a=1, b=2, c=3)
+
+    with pytest.raises(TypeError):
+        utils.call_with_supported_arguments(foo, a=1)