From 00b28610db1a7fc7c49367a2ef9e8534c4d5db53 Mon Sep 17 00:00:00 2001
From: Jimmy Jia <tesrin@gmail.com>
Date: Mon, 19 Nov 2018 10:38:14 -0500
Subject: [PATCH] Inspect violated constraints

---
 flask_resty/view.py       | 46 ++++++++++++++++++++++++++++++---------
 tests/test_view_errors.py | 16 +++++++++++++-
 2 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/flask_resty/view.py b/flask_resty/view.py
index a1089d3..386d8ee 100644
--- a/flask_resty/view.py
+++ b/flask_resty/view.py
@@ -3,6 +3,7 @@
 import flask
 from flask.views import MethodView
 from marshmallow import fields
+import sqlalchemy as sa
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Load
 from sqlalchemy.orm.exc import NoResultFound
@@ -415,20 +416,45 @@ def commit(self):
     def resolve_integrity_error(self, error):
         original_error = error.orig
 
-        if (
-            hasattr(original_error, 'pgcode') and
-            original_error.pgcode in (
+        if hasattr(original_error, 'pgcode'):
+            if original_error.pgcode in (
                 '23502',  # not_null_violation
                 '23514',  # check_violation
-            )
-        ):
-            # Using the psycopg2 error code, we can tell that this was not from
-            # an integrity error that was not a conflict. This means there was
-            # a schema bug, so we emit an interal server error instead.
-            return error
+            ):
+                # Using the psycopg2 error code, we can tell that this was not
+                # from an integrity error that was not a conflict. This means
+                # there was a schema bug, so we emit an internal server error
+                # instead.
+                return error
+            else:
+                diag = original_error.diag
+
+                schema_name = diag.schema_name
+                table_name = diag.table_name
+                constraint_name = diag.constraint_name
+
+                insp = sa.inspect(self.session.bind)
+                unique_constraints = insp.get_unique_constraints(
+                    table_name,
+                    schema=schema_name,
+                )
+
+                for unique_constraint in unique_constraints:
+                    if unique_constraint['name'] == constraint_name:
+                        column_names = unique_constraint['column_names']
+                        break
+                else:
+                    column_names = ()
+        else:
+            column_names = ()
 
         flask.current_app.logger.exception("handled integrity error")
-        return ApiError(409, {'code': 'invalid_data.conflict'})
+
+        error = {'code': 'invalid_data.conflict'}
+        if column_names:
+            error['source'] = {'pointer': '/data/{}'.format(column_names[-1])}
+
+        return ApiError(409, error)
 
     def set_item_response_meta(self, item):
         super(ModelView, self).set_item_response_meta(item)
diff --git a/tests/test_view_errors.py b/tests/test_view_errors.py
index 1309045..9380c28 100644
--- a/tests/test_view_errors.py
+++ b/tests/test_view_errors.py
@@ -230,10 +230,24 @@ def test_integrity_error_conflict(client, path):
     }])
 
 
+@pytest.mark.parametrize('path', ('/widgets', '/widgets_flush'))
+def test_integrity_error_conflict_with_source(db, client, path):
+    if db.engine.driver != 'psycopg2':
+        pytest.xfail("IntegrityError source detection requires psycopg2")
+
+    response = client.post(path, data={
+        'name': "Foo",
+    })
+    assert_response(response, 409, [{
+        'code': 'invalid_data.conflict',
+        'source': {'pointer': '/data/name'},
+    }])
+
+
 @pytest.mark.parametrize('path', ('/widgets', '/widgets_flush'))
 def test_integrity_error_uncaught(db, app, client, path):
     if db.engine.driver != 'psycopg2':
-        pytest.xfail("IntegrityError cause detection only works with psycopg2")
+        pytest.xfail("IntegrityError cause detection requires psycopg2")
 
     app.testing = False