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[python] fix regex validator for date-time fields with a pattern #24105

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[python] fix regex validator for date-time fields with a pattern #24105

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77ef30f
[python] fix regex validator for date-time fields with a pattern
timonrieger Jun 23, 2026
fa1328e
samples
timonrieger Jun 23, 2026
5ffba67
document fix
timonrieger Jun 23, 2026
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7 changes: 3 additions & 4 deletions modules/openapi-generator/src/main/resources/python/model_generic.mustache
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Original file line number Diff line number Diff line change
Expand Up @@ -53,10 +53,9 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}

{{/isNullable}}
{{/required}}
if not isinstance(value, str):
value = str(value)

if not re.match(r"{{{.}}}", value{{#vendorExtensions.x-modifiers}} ,re.{{{.}}}{{/vendorExtensions.x-modifiers}}):
# match against the ISO string of parsed values (e.g. datetime) without mutating value
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
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@cubic-dev-ai cubic-dev-ai Bot Jun 23, 2026

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P2: Pattern validation uses isoformat() which normalizes datetime representations (e.g., Z → +00:00), causing valid inputs matching patterns that expect the original lexical form to incorrectly fail validation.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/python/model_generic.mustache, line 57:

<comment>Pattern validation uses isoformat() which normalizes datetime representations (e.g., Z → +00:00), causing valid inputs matching patterns that expect the original lexical form to incorrectly fail validation.</comment>

<file context>
@@ -53,10 +53,9 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
-
-        if not re.match(r"{{{.}}}", value{{#vendorExtensions.x-modifiers}} ,re.{{{.}}}{{/vendorExtensions.x-modifiers}}):
+        # match against the ISO string of parsed values (e.g. datetime) without mutating value
+        s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
+        if not re.match(r"{{{.}}}", s{{#vendorExtensions.x-modifiers}} ,re.{{{.}}}{{/vendorExtensions.x-modifiers}}):
             raise ValueError(r"must validate the regular expression {{{vendorExtensions.x-pattern}}}")
</file context>

if not re.match(r"{{{.}}}", s{{#vendorExtensions.x-modifiers}} ,re.{{{.}}}{{/vendorExtensions.x-modifiers}}):
raise ValueError(r"must validate the regular expression {{{vendorExtensions.x-pattern}}}")
return value
{{/vendorExtensions.x-regex}}
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11 changes: 11 additions & 0 deletions ...napi-generator/src/test/java/org/openapitools/codegen/python/PythonClientCodegenTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -670,6 +670,17 @@ public void testUuidWithPatternImportsFieldValidator() throws IOException {
assertFileContains(p, "from pydantic import BaseModel, ConfigDict, field_validator");
}

@Test(description = "date-time property with pattern should coerce via isoformat() before regex match")
public void testDatetimeWithPatternUsesIsoformat() throws IOException {
final DefaultCodegen codegen = new PythonClientCodegen();
final String outputPath = generateFiles(codegen, "src/test/resources/bugs/issue_datetime_with_pattern.yaml");
final Path p = Paths.get(outputPath + "openapi_client/models/datetime_with_pattern.py");

assertFileExists(p);
assertFileContains(p, "s = value if isinstance(value, str) else value.isoformat() if hasattr(value, \"isoformat\") else str(value)");
TestUtils.assertFileNotContains(p, "return s");
}

@Test(description = "Verify default buildSystem uses setuptools")
public void testDefaultBuildSystemSetuptools() throws IOException {
File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
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14 changes: 14 additions & 0 deletions modules/openapi-generator/src/test/resources/bugs/issue_datetime_with_pattern.yaml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
openapi: 3.0.0
info:
title: Test date-time with pattern
version: 1.0.0
paths: {}
components:
schemas:
DatetimeWithPattern:
type: object
properties:
created_at:
type: string
format: date-time
pattern: "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}(?:\\.\\d+)?(?:Z|[+-]\\d{2}:\\d{2})$"
24 changes: 8 additions & 16 deletions samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/format_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -56,10 +56,8 @@ def string_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"[a-z]", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"[a-z]", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /[a-z]/i")
return value

Expand All @@ -69,10 +67,8 @@ def string_with_double_quote_pattern_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"this is \"something\"", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"this is \"something\"", s):
raise ValueError(r"must validate the regular expression /this is \"something\"/")
return value

Expand All @@ -82,10 +78,8 @@ def pattern_with_digits_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^\d{10}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^\d{10}$", s):
raise ValueError(r"must validate the regular expression /^\d{10}$/")
return value

Expand All @@ -95,10 +89,8 @@ def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^image_\d{1,3}$", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
return value

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6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/nullable_property.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,8 @@ def name_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[A-Z].*", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[A-Z].*", s):
raise ValueError(r"must validate the regular expression /^[A-Z].*/")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/uuid_with_pattern.py
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Expand Up @@ -37,10 +37,8 @@ def id_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", s):
raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
return value

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24 changes: 8 additions & 16 deletions samples/openapi3/client/petstore/python-httpx/petstore_api/models/format_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -56,10 +56,8 @@ def string_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"[a-z]", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"[a-z]", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /[a-z]/i")
return value

Expand All @@ -69,10 +67,8 @@ def string_with_double_quote_pattern_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"this is \"something\"", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"this is \"something\"", s):
raise ValueError(r"must validate the regular expression /this is \"something\"/")
return value

Expand All @@ -82,10 +78,8 @@ def pattern_with_digits_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^\d{10}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^\d{10}$", s):
raise ValueError(r"must validate the regular expression /^\d{10}$/")
return value

Expand All @@ -95,10 +89,8 @@ def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^image_\d{1,3}$", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python-httpx/petstore_api/models/nullable_property.py
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Expand Up @@ -38,10 +38,8 @@ def name_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[A-Z].*", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)

@cubic-dev-ai cubic-dev-ai Bot Jun 23, 2026

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P2: Non-string conversion branches in pattern validator are dead code for this strict string field

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At samples/openapi3/client/petstore/python-httpx/petstore_api/models/nullable_property.py, line 41:

<comment>Non-string conversion branches in pattern validator are dead code for this strict string field</comment>

<file context>
@@ -38,10 +38,8 @@ def name_validate_regular_expression(cls, value):
-            value = str(value)
-
-        if not re.match(r"^[A-Z].*", value):
+        s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
+        if not re.match(r"^[A-Z].*", s):
             raise ValueError(r"must validate the regular expression /^[A-Z].*/")
</file context>

if not re.match(r"^[A-Z].*", s):
raise ValueError(r"must validate the regular expression /^[A-Z].*/")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python-httpx/petstore_api/models/uuid_with_pattern.py
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Original file line number Diff line number Diff line change
Expand Up @@ -37,10 +37,8 @@ def id_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", s):
raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
return value

Expand Down
24 changes: 8 additions & 16 deletions samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/format_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,10 +57,8 @@ def string_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"[a-z]", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"[a-z]", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /[a-z]/i")
return value

Expand All @@ -70,10 +68,8 @@ def string_with_double_quote_pattern_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"this is \"something\"", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"this is \"something\"", s):
raise ValueError(r"must validate the regular expression /this is \"something\"/")
return value

Expand All @@ -83,10 +79,8 @@ def pattern_with_digits_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^\d{10}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^\d{10}$", s):
raise ValueError(r"must validate the regular expression /^\d{10}$/")
return value

Expand All @@ -96,10 +90,8 @@ def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^image_\d{1,3}$", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/nullable_property.py
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Original file line number Diff line number Diff line change
Expand Up @@ -39,10 +39,8 @@ def name_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[A-Z].*", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[A-Z].*", s):
raise ValueError(r"must validate the regular expression /^[A-Z].*/")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/uuid_with_pattern.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,8 @@ def id_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", s):
raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
return value

Expand Down
24 changes: 8 additions & 16 deletions samples/openapi3/client/petstore/python/petstore_api/models/format_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,10 +57,8 @@ def string_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"[a-z]", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"[a-z]", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /[a-z]/i")
return value

Expand All @@ -70,10 +68,8 @@ def string_with_double_quote_pattern_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"this is \"something\"", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"this is \"something\"", s):
raise ValueError(r"must validate the regular expression /this is \"something\"/")
return value

Expand All @@ -83,10 +79,8 @@ def pattern_with_digits_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^\d{10}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^\d{10}$", s):
raise ValueError(r"must validate the regular expression /^\d{10}$/")
return value

Expand All @@ -96,10 +90,8 @@ def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^image_\d{1,3}$", s ,re.IGNORECASE):
raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python/petstore_api/models/nullable_property.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -39,10 +39,8 @@ def name_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[A-Z].*", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[A-Z].*", s):
raise ValueError(r"must validate the regular expression /^[A-Z].*/")
return value

Expand Down
6 changes: 2 additions & 4 deletions samples/openapi3/client/petstore/python/petstore_api/models/uuid_with_pattern.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,8 @@ def id_validate_regular_expression(cls, value):
if value is None:
return value

if not isinstance(value, str):
value = str(value)

if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
s = value if isinstance(value, str) else value.isoformat() if hasattr(value, "isoformat") else str(value)
if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", s):
raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
return value

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