Add tests

tests/test_types.py

@@ -3936,6 +3936,39 @@ class Foobar(BaseModel):
     }
 
 
+@pytest.mark.parametrize(
+    'use_compiled_pattern',
+    [True, False],
+)
+def test_pattern_field(use_compiled_pattern):
+    pattern_value = r'^whatev.r\d$'
+
+    field_pattern = pattern_value
+    if use_compiled_pattern:
+        field_pattern = re.compile(pattern_value)
+
+    class Foobar(BaseModel):
+        a: str = Field(..., pattern=field_pattern)
+
+    matching_value = 'whatever1'
+    f = Foobar(a=matching_value)
+    assert f.a == matching_value
+
+    # Check that pre-compiled patterns are accepted unchanged
+    with pytest.raises(
+        ValidationError,
+        match=re.escape(r"String should match pattern '^whatev.r\d$'."),
+    ):
+        Foobar(a=' whatever1')
+
+    assert Foobar.model_json_schema() == {
+        'type': 'object',
+        'title': 'Foobar',
+        'properties': {'a': {'pattern': pattern_value, 'title': 'A', 'type': 'string'}},
+        'required': ['a'],
+    }
+
+
 def test_pattern_with_invalid_param():
     with pytest.raises(
         PydanticSchemaGenerationError,