[khayashi4337]

With pythonic_params=True, which the generated python-flask and python-aiohttp servers use, Connexion renames parameters with snake_and_shadow(): snake_case, then a trailing _ if the name is a Python builtin or, since Connexion 2.10, a keyword. The generator named the handler arguments differently. It added a leading _ for its own reserved words and left builtins unchanged. As a result:

• a path parameter id produced def get_thing(id, ...) while Connexion calls get_thing(id_=...), so every request fails with TypeError (500);
• query parameters such as filter, type or format are silently dropped.

Changes

AbstractPythonConnexionServerCodegen.toParamName():

• appends _ to Python builtins (a fixed list of the lowercase dir(builtins) names; it matches Python 3.11 and 3.14 exactly) and to keywords, like Connexion;
• keeps leading underscores (_from stays _from) and passes callback through unchanged, as Connexion does;
• keeps the previous naming for header and cookie parameters. Connexion never passes these to the handler (they are read from the request), so they keep a name such as _json that doesn't shadow modules like json.

python-blueplanet opts out (usesPythonicParams() returns false). Its generated app doesn't set pythonic_params, so Connexion 1.x passes the original names.

The wire names don't change: x-python-connexion-openapi-name restores them in the generated openapi.yaml, now also for parameters defined under components/parameters. The generated controller tests send form data under the wire names too.

A side effect: names that the generator reserved but that are neither builtins nor keywords (date, self, schema, ...) now become date instead of _date, which is what Connexion passes.

Verification

• Python*Test / AbstractPython*Test pass. The new tests cover flask, aiohttp and blueplanet signatures, _from, callback, date/self, a JSON header named json, a $ref parameter, and form keys.
• Generated python-flask and python-aiohttp servers from a spec with path id and query filter, type, format, from, pageSize, plus _from, callback, date, self and a JSON header json. On Connexion 2.14.2, the requests return 200 with every value delivered (id_, filter_, type_, format_, from_, page_size, _from, callback, date, self, _json). With the generator from master, the same GET /probe/abc fails with TypeError: unexpected keyword argument 'id_'.
• bin/generate-samples.sh bin/configs/python*.yaml produces no diff; none of the sample specs use such names.

Known remaining differences / not in this PR

• Names that Connexion's inflection.underscore() and the generator's underscore() still convert differently: acronyms (HTTPId), names with dots or other separators, and names starting with a digit. A spec with both id and id_ can't work either, because Connexion maps both to id_.
• The builtins list follows current Pythons: aiter/anext (3.10+) and breakpoint (3.7+) would still mismatch on older interpreters.
• Pre-existing and unchanged: application/x-www-form-urlencoded request bodies fail on master too (missing 1 required positional argument). Connexion passes the form as a single body argument, while the generated handler expects one argument per field.

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  Regenerated all bin/configs/python*.yaml samples: no diff. Generator options and docs are unchanged.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

cc @cbornet @tomplus @krjakbrjak @fa0311 (Python technical committee)

Parts of this change were drafted with AI coding assistants (Devin, Claude Code, with reviews by Codex and Fable) and reviewed and verified by me.

🤖 Generated with Claude Code

---

Summary by cubic

Fixes generated python-flask and python-aiohttp handlers to name arguments the way Connexion actually passes them (pythonic_params=True). Previously, a path param id became id in the signature while Connexion sent id_, causing a TypeError (500) on every request; query params like filter, type, and format were silently dropped because the handler argument names didn't match.

• Builtins and keywords now get a trailing underscore (id_, filter_, from_), matching Connexion's snake_and_shadow().
• Header and cookie params keep the previous naming, since Connexion reads them from the request and never passes them to the handler.
• Wire names in the generated openapi.yaml are preserved via the existing x-python-connexion-openapi-name extension, now also for parameters under components/parameters.
• Generated controller tests send form data under the wire names.
• python-blueplanet opts out of the new naming because its generated app doesn't set pythonic_params (Connexion 1.x).

^{Written for commit 0090f1f. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 7 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. When an issue isn't valid or won't be fixed in this PR, reply in its thread with the reason and then resolve the thread. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java:58">
P2: The hardcoded builtin list is newer than the supported Python floor: Python 3.5 does not define `aiter`, `anext`, or `breakpoint`, but this generator still emits suffixed handler names that Connexion will not pass. Keep the reserved-name set compatible with the supported interpreter floor or derive it from the same runtime/version constraints as Connexion.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

View guided diff | Re-trigger cubic</sub>

[cubic-dev-ai]

P2: The hardcoded builtin list is newer than the supported Python floor: Python 3.5 does not define aiter, anext, or breakpoint, but this generator still emits suffixed handler names that Connexion will not pass. Keep the reserved-name set compatible with the supported interpreter floor or derive it from the same runtime/version constraints as Connexion.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. When an issue isn't valid or won't be fixed in this PR, reply in its thread with the reason and then resolve the thread. At modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java, line 58:

<comment>The hardcoded builtin list is newer than the supported Python floor: Python 3.5 does not define `aiter`, `anext`, or `breakpoint`, but this generator still emits suffixed handler names that Connexion will not pass. Keep the reserved-name set compatible with the supported interpreter floor or derive it from the same runtime/version constraints as Connexion.</comment>

<file context>
@@ -50,8 +50,22 @@
 public abstract class AbstractPythonConnexionServerCodegen extends AbstractPythonCodegen implements CodegenConfig {
+    protected static final Set<String> PYTHON_BUILTINS = Set.of(
+            "abs", "aiter", "all", "anext", "any", "ascii", "bin", "bool",
+            "breakpoint", "bytearray", "bytes", "callable", "chr", "classmethod",
+            "compile", "complex", "copyright", "credits", "delattr", "dict",
+            "dir", "divmod", "enumerate", "eval", "exec", "exit", "filter",
</file context>

[khayashi4337]

Valid, but I've left the list as is on purpose. Connexion decides at runtime, from the builtins of the Python it's running on, so a fixed list can't match every interpreter: whichever version I pick, some other version disagrees. Tracking the oldest Python would make aiter/anext (3.10+) and breakpoint (3.7+) mismatch on every current interpreter instead.

I followed current Pythons, because the generated servers depend on Connexion >= 2.6, which needs Python >= 3.6. Parameters with these three names are also very unlikely. The PR description already listed aiter/anext as a known difference, and I've added breakpoint there too.