🥅 Don't suppress SQLAlchemy errors when mapping classes (#169)

These changes modify graphene-sqlalchemy so as not to suppress errors coming
from SQLAlchemy when attempting to map classes. Previously this made the
debugging experience difficult since issues with SQLAlchemy models
would produce an unclear error message from graphene-sqlalchemy. With
these changes, the SQLAlchemy error is propagated to the end-user,
allowing them to correct the real issue quickly.

Fixes #121

.pre-commit-config.yaml

@@ -1,7 +1,7 @@
 default_language_version:
     python: python3.7
 repos:
--   repo: git://github.com/pre-commit/pre-commit-hooks
+-   repo: https://github.com/pre-commit/pre-commit-hooks
     rev: c8bad492e1b1d65d9126dba3fe3bd49a5a52b9d6  # v2.1.0
     hooks:
     -   id: check-merge-conflict
@@ -11,15 +11,15 @@ repos:
         exclude: ^docs/.*$
     -   id: trailing-whitespace
         exclude: README.md
--   repo: git://github.com/PyCQA/flake8
+-   repo: https://github.com/PyCQA/flake8
     rev: 88caf5ac484f5c09aedc02167c59c66ff0af0068  # 3.7.7
     hooks:
     -   id: flake8
--   repo: git://github.com/asottile/seed-isort-config
+-   repo: https://github.com/asottile/seed-isort-config
     rev: v1.7.0
     hooks:
     -   id: seed-isort-config
--   repo: git://github.com/pre-commit/mirrors-isort
+-   repo: https://github.com/pre-commit/mirrors-isort
     rev: v4.3.4
     hooks:
     -   id: isort

graphene_sqlalchemy/tests/test_types.py

@@ -1,11 +1,14 @@
 from unittest import mock
 
 import pytest
+import sqlalchemy.exc
+import sqlalchemy.orm.exc
 
 from graphene import (Dynamic, Field, GlobalID, Int, List, Node, NonNull,
                       ObjectType, Schema, String)
 from graphene.relay import Connection
 
+from .. import utils
 from ..converter import convert_sqlalchemy_composite
 from ..fields import (SQLAlchemyConnectionField,
                       UnsortedSQLAlchemyConnectionField, createConnectionField,
@@ -492,3 +495,65 @@ class Meta:
 def test_deprecated_createConnectionField():
     with pytest.warns(DeprecationWarning):
         createConnectionField(None)
+
+
+@mock.patch(utils.__name__ + '.class_mapper')
+def test_unique_errors_propagate(class_mapper_mock):
+    # Define unique error to detect
+    class UniqueError(Exception):
+        pass
+
+    # Mock class_mapper effect
+    class_mapper_mock.side_effect = UniqueError
+
+    # Make sure that errors are propagated from class_mapper when instantiating new classes
+    error = None
+    try:
+        class ArticleOne(SQLAlchemyObjectType):
+            class Meta(object):
+                model = Article
+    except UniqueError as e:
+        error = e
+
+    # Check that an error occured, and that it was the unique error we gave
+    assert error is not None
+    assert isinstance(error, UniqueError)
+
+
+@mock.patch(utils.__name__ + '.class_mapper')
+def test_argument_errors_propagate(class_mapper_mock):
+    # Mock class_mapper effect
+    class_mapper_mock.side_effect = sqlalchemy.exc.ArgumentError
+
+    # Make sure that errors are propagated from class_mapper when instantiating new classes
+    error = None
+    try:
+        class ArticleTwo(SQLAlchemyObjectType):
+            class Meta(object):
+                model = Article
+    except sqlalchemy.exc.ArgumentError as e:
+        error = e
+
+    # Check that an error occured, and that it was the unique error we gave
+    assert error is not None
+    assert isinstance(error, sqlalchemy.exc.ArgumentError)
+
+
+@mock.patch(utils.__name__ + '.class_mapper')
+def test_unmapped_errors_reformat(class_mapper_mock):
+    # Mock class_mapper effect
+    class_mapper_mock.side_effect = sqlalchemy.orm.exc.UnmappedClassError(object)
+
+    # Make sure that errors are propagated from class_mapper when instantiating new classes
+    error = None
+    try:
+        class ArticleThree(SQLAlchemyObjectType):
+            class Meta(object):
+                model = Article
+    except ValueError as e:
+        error = e
+
+    # Check that an error occured, and that it was the unique error we gave
+    assert error is not None
+    assert isinstance(error, ValueError)
+    assert "You need to pass a valid SQLAlchemy Model" in str(error)

graphene_sqlalchemy/types.py

@@ -207,9 +207,11 @@ def __init_subclass_with_meta__(
         _meta=None,
         **options
     ):
-        assert is_mapped_class(model), (
-            "You need to pass a valid SQLAlchemy Model in " '{}.Meta, received "{}".'
-        ).format(cls.__name__, model)
+        # Make sure model is a valid SQLAlchemy model
+        if not is_mapped_class(model):
+            raise ValueError(
+                "You need to pass a valid SQLAlchemy Model in " '{}.Meta, received "{}".'.format(cls.__name__, model)
+            )
 
         if not registry:
             registry = get_global_registry()

graphene_sqlalchemy/utils.py

@@ -27,7 +27,13 @@ def get_query(model, context):
 def is_mapped_class(cls):
     try:
         class_mapper(cls)
-    except (ArgumentError, UnmappedClassError):
+    except ArgumentError as error:
+        # Only handle ArgumentErrors for non-class objects
+        if "Class object expected" in str(error):
+            return False
+        raise
+    except UnmappedClassError:
+        # Unmapped classes return false
         return False
     else:
         return True