Fix creating schema from model using ConstrainedStr with regex str as dict key (#5223)

* add test for failing schema generation using ConstrainedStr as dict key

* move get_pattern from ConstrainedStr to utils.py, use in schema.py when accessing pattern in regex

* add change description md

* move new test cases into existing test_schema_dict_constr test

* undo moving get_pattern to utils.py, directly use ConstrainedStr._get_pattern function in schema.py instead

* pull tests for ConstrainedStr model into separate def

* use markdown backticks in change description.

---------

Co-authored-by: Simon Matejetz <[email protected]>
Co-authored-by: Samuel Colvin <[email protected]>

Author: 3 people

changes/5223-matejetz.md

@@ -0,0 +1 @@
+Fix creating schema from model using `ConstrainedStr` with `regex` as dict key

pydantic/schema.py

@@ -55,6 +55,7 @@
     ConstrainedInt,
     ConstrainedList,
     ConstrainedSet,
+    ConstrainedStr,
     SecretBytes,
     SecretStr,
     StrictBytes,
@@ -490,7 +491,7 @@ def field_type_schema(
         if regex:
             # Dict keys have a regex pattern
             # items_schema might be a schema or empty dict, add it either way
-            f_schema['patternProperties'] = {regex.pattern: items_schema}
+            f_schema['patternProperties'] = {ConstrainedStr._get_pattern(regex): items_schema}
         if items_schema:
             # The dict values are not simply Any, so they need a schema
             f_schema['additionalProperties'] = items_schema

tests/test_schema.py

@@ -1,6 +1,7 @@
 import json
 import math
 import os
+import re
 import sys
 import tempfile
 from datetime import date, datetime, time, timedelta
@@ -20,6 +21,7 @@
     NamedTuple,
     NewType,
     Optional,
+    Pattern,
     Set,
     Tuple,
     Type,
@@ -3256,3 +3258,27 @@ class Baz(BaseModel):
         'properties': {'a': {'title': 'A'}, 'b': {'title': 'B'}},
         'required': ['a', 'b'],
     }
+
+
+@pytest.mark.parametrize(
+    'regex_val',
+    [
+        '^text$',
+        re.compile('^text$'),
+    ],
+)
+def test_constrained_str_class_dict(regex_val: Union[str, Pattern[str]]):
+    class CustomStr(ConstrainedStr):
+        regex = regex_val
+
+    class Model(BaseModel):
+        a: Dict[CustomStr, Any]
+
+    json_schema = Model.schema()
+
+    assert json_schema == {
+        'title': 'Model',
+        'type': 'object',
+        'properties': {'a': {'patternProperties': {'^text$': {}}, 'title': 'A', 'type': 'object'}},
+        'required': ['a'],
+    }