Handle case when 422 error does not have a 'field' value (#83)

gidgethub/__init__.py

@@ -71,6 +71,20 @@ def __init__(self, errors: Any, *args: Any) -> None:
         super().__init__(http.HTTPStatus.UNPROCESSABLE_ENTITY, *args)
 
 
+class ValidationError(BadRequest):
+
+    """A request was unable to be completed.
+
+    Represented by a 422 HTTP Response. Details of what went wrong
+    are stored in the errors attribute.
+    """
+
+    def __init__(self, errors: Any, *args: Any) -> None:
+        """Store the error details."""
+        self.errors = errors
+        super().__init__(http.HTTPStatus.UNPROCESSABLE_ENTITY, *args)
+
+
 class GitHubBroken(HTTPException):
 
     """Exception for 5XX HTTP responses."""

gidgethub/sansio.py

@@ -18,7 +18,8 @@
 import uritemplate
 
 from . import (BadRequest, GitHubBroken, HTTPException, InvalidField,
-               RateLimitExceeded, RedirectionException, ValidationFailure)
+               RateLimitExceeded, RedirectionException, ValidationError,
+               ValidationFailure)
 
 
 def _parse_content_type(content_type: Optional[str]) -> Tuple[Optional[str], str]:
@@ -307,12 +308,19 @@ def decipher_response(status_code: int, headers: Mapping[str, str],
                     raise RateLimitExceeded(rate_limit, message)
             elif status_code == 422:
                 errors = data.get("errors", None)
+                exc_type = InvalidField
                 if errors:
-                    fields = ", ".join(repr(e["field"]) for e in errors)
-                    message = f"{message} for {fields}"
+                    if any(e['code'] in ['missing', 'missing_field', 'invalid', 'already_exists']
+                           for e in errors):
+                        error_context = ", ".join(repr(e.get("field")) for e in errors)
+                        message = f"{message} for {error_context}"
+                    else:
+                        exc_type = ValidationError
+                        error_context = ", ".join(repr(e.get("message")) for e in errors)
+                        message = f"{message}: {error_context}"
                 else:
                     message = data["message"]
-                raise InvalidField(errors, message)
+                raise exc_type(errors, message)
         elif status_code >= 300:
             exc_type = RedirectionException
         else:

gidgethub/test/test_sansio.py

@@ -7,7 +7,8 @@
 import pytest
 
 from .. import (BadRequest, GitHubBroken, HTTPException, InvalidField,
-                RateLimitExceeded, RedirectionException, ValidationFailure)
+                RateLimitExceeded, RedirectionException, ValidationError,
+                ValidationFailure)
 from .. import sansio
 
 
@@ -320,6 +321,20 @@ def test_422(self):
         assert exc_info.value.status_code == http.HTTPStatus(status_code)
         assert str(exc_info.value) == "it went bad for 'title'"
 
+    def test_422_custom_code(self):
+        status_code = 422
+        errors = [
+            {"resource": "PullRequest", "code": "custom",
+             "message": "A pull request already exists for foo:1."},
+        ]
+        body = json.dumps({"message": "it went bad", "errors": errors})
+        body = body.encode("utf-8")
+        headers = {"content-type": "application/json; charset=utf-8"}
+        with pytest.raises(ValidationError) as exc_info:
+            sansio.decipher_response(status_code, headers, body)
+        assert exc_info.value.status_code == http.HTTPStatus(status_code)
+        assert str(exc_info.value) == "it went bad: 'A pull request already exists for foo:1.'"
+
     def test_422_no_errors_object(self):
         status_code = 422
         body = json.dumps({"message": "Reference does not exist",