[python][asyncio] Expose ClientSession extension points (closes OpenAPITools#23830) (OpenAPITools#23847)

* [python][asyncio] Expose ClientSession extension points (closes OpenAPITools#23830)

Mirror the python/httpx template's `_create_pool_manager()` factory and add a
parallel `_create_connector()` so subclasses can customize the
`aiohttp.ClientSession` / `aiohttp.TCPConnector` without overriding `request()`.

Also surface three typed fields on `Configuration` (asyncio block):
  - `trace_configs: list[aiohttp.TraceConfig]` — forwarded to `ClientSession`
    for tracing / instrumentation (OpenTelemetry, etc.). This was the original
    issue request.
  - `tcp_connector_limit_per_host: int` — per-host concurrency cap forwarded
    to `aiohttp.TCPConnector(limit_per_host=...)`.
  - `client_session_kwargs: dict` — merged into `ClientSession(**kwargs)` for
    less common knobs (`json_serialize=orjson.dumps`,
    `cookie_jar=aiohttp.DummyCookieJar()`, `raise_for_status=...`).

All new Configuration fields are read via `getattr(self.configuration, ..., None)`
so older Configuration objects (e.g. produced by an older generator version
and passed manually) remain compatible. The httpx template is left untouched;
only the asyncio side is changed in this PR. No Java code change is needed —
the `{{#asyncio}}` mustache block already gates the new code path.

Closes OpenAPITools#23830

* update python-aiohttp samples

---------

Co-authored-by: liqiankun.1111 <liqiankun.1111@bytedance.com>

Author: qiankunli

modules/openapi-generator/src/main/resources/python/asyncio/rest.mustache

@@ -7,7 +7,7 @@ import io
 import json
 import re
 import ssl
-from typing import Optional, Union
+from typing import Any, Dict, Optional, Union
 
 import aiohttp
 import aiohttp_retry
@@ -49,6 +49,10 @@ class RESTClientObject:
 
     def __init__(self, configuration) -> None:
 
+        # Keep a reference so factory methods (_create_pool_manager / _create_connector)
+        # and subclasses can read extension fields like trace_configs.
+        self.configuration = configuration
+
         # maxsize is number of requests to host that are allowed in parallel
         self.maxsize = configuration.connection_pool_maxsize
 
@@ -92,6 +96,40 @@ class RESTClientObject:
         if self.retry_client is not None:
             await self.retry_client.close()
 
+    def _create_connector(self) -> aiohttp.TCPConnector:
+        """Build the TCPConnector used by the ClientSession.
+
+        Override in a subclass to customize DNS resolver, keepalive, etc.
+        """
+        kwargs: Dict[str, Any] = {
+            "limit": self.maxsize,
+            "ssl": self.ssl_context,
+        }
+        limit_per_host = getattr(self.configuration, "tcp_connector_limit_per_host", None)
+        if limit_per_host is not None:
+            kwargs["limit_per_host"] = limit_per_host
+        return aiohttp.TCPConnector(**kwargs)
+
+    def _create_pool_manager(self) -> aiohttp.ClientSession:
+        """Build the aiohttp.ClientSession used as the connection pool.
+
+        Override in a subclass to fully customize the session (e.g. attach
+        aiohttp.TraceConfig, swap json_serialize, etc.). Typed Configuration
+        fields (trace_configs / client_session_kwargs) are read via getattr
+        so older Configuration objects remain compatible.
+        """
+        kwargs: Dict[str, Any] = {
+            "connector": self._create_connector(),
+            "trust_env": True,
+        }
+        trace_configs = getattr(self.configuration, "trace_configs", None)
+        if trace_configs is not None:
+            kwargs["trace_configs"] = trace_configs
+        extra = getattr(self.configuration, "client_session_kwargs", None)
+        if extra:
+            kwargs.update(extra)
+        return aiohttp.ClientSession(**kwargs)
+
     async def request(
         self,
         method,
@@ -200,10 +238,7 @@ class RESTClientObject:
 
         # https pool manager
         if self.pool_manager is None:
-            self.pool_manager = aiohttp.ClientSession(
-                connector=aiohttp.TCPConnector(limit=self.maxsize, ssl=self.ssl_context),
-                trust_env=True,
-            )
+            self.pool_manager = self._create_pool_manager()
         pool_manager = self.pool_manager
 
         if self._effective_retry_options is not None and method in ALLOW_RETRY_METHODS:

modules/openapi-generator/src/main/resources/python/configuration.mustache

@@ -1,6 +1,7 @@
 {{>partial_header}}
 
 {{#asyncio}}
+import aiohttp
 import aiohttp_retry
 {{/asyncio}}
 {{#async}}
@@ -192,6 +193,13 @@ class Configuration:
       in PEM format.
 {{#asyncio}}
     :param retries: int | aiohttp_retry.RetryOptionsBase - Retry configuration.
+    :param trace_configs: list of aiohttp.TraceConfig instances forwarded to
+      aiohttp.ClientSession for tracing/instrumentation (e.g. OpenTelemetry).
+    :param tcp_connector_limit_per_host: Per-host concurrency cap forwarded to
+      aiohttp.TCPConnector(limit_per_host=...). None leaves aiohttp's default (0 = unlimited).
+    :param client_session_kwargs: Extra keyword arguments merged into
+      aiohttp.ClientSession(**kwargs) (e.g. json_serialize=orjson.dumps,
+      cookie_jar=aiohttp.DummyCookieJar()).
 {{/asyncio}}
 {{#httpx}}
     :param retries: int - Retry configuration.
@@ -320,6 +328,9 @@ conf = {{{packageName}}}.Configuration(
         ssl_ca_cert: Optional[str]=None,
 {{#asyncio}}
         retries: Optional[Union[int, aiohttp_retry.RetryOptionsBase]] = None,
+        trace_configs: Optional[List[aiohttp.TraceConfig]] = None,
+        tcp_connector_limit_per_host: Optional[int] = None,
+        client_session_kwargs: Optional[Dict[str, Any]] = None,
 {{/asyncio}}
 {{#httpx}}
         retries: Optional[int] = None,
@@ -470,6 +481,17 @@ conf = {{{packageName}}}.Configuration(
         self.retries = retries
         """Retry configuration
         """
+{{#asyncio}}
+        self.trace_configs = trace_configs
+        """aiohttp.TraceConfig list forwarded to ClientSession for tracing.
+        """
+        self.tcp_connector_limit_per_host = tcp_connector_limit_per_host
+        """Per-host concurrency cap forwarded to TCPConnector.
+        """
+        self.client_session_kwargs = client_session_kwargs
+        """Extra kwargs merged into aiohttp.ClientSession(**kwargs).
+        """
+{{/asyncio}}
         # Enable client side validation
         self.client_side_validation = client_side_validation
 

samples/openapi3/client/petstore/python-aiohttp/petstore_api/configuration.py

@@ -10,6 +10,7 @@
 """  # noqa: E501
 
 
+import aiohttp
 import aiohttp_retry
 import base64
 import copy
@@ -169,6 +170,13 @@ class Configuration:
     :param ssl_ca_cert: str - the path to a file of concatenated CA certificates
       in PEM format.
     :param retries: int | aiohttp_retry.RetryOptionsBase - Retry configuration.
+    :param trace_configs: list of aiohttp.TraceConfig instances forwarded to
+      aiohttp.ClientSession for tracing/instrumentation (e.g. OpenTelemetry).
+    :param tcp_connector_limit_per_host: Per-host concurrency cap forwarded to
+      aiohttp.TCPConnector(limit_per_host=...). None leaves aiohttp's default (0 = unlimited).
+    :param client_session_kwargs: Extra keyword arguments merged into
+      aiohttp.ClientSession(**kwargs) (e.g. json_serialize=orjson.dumps,
+      cookie_jar=aiohttp.DummyCookieJar()).
     :param ca_cert_data: verify the peer using concatenated CA certificate data
       in PEM (str) or DER (bytes) format.
     :param cert_file: the path to a client certificate file, for mTLS.
@@ -279,6 +287,9 @@ def __init__(
         ignore_operation_servers: bool=False,
         ssl_ca_cert: Optional[str]=None,
         retries: Optional[Union[int, aiohttp_retry.RetryOptionsBase]] = None,
+        trace_configs: Optional[List[aiohttp.TraceConfig]] = None,
+        tcp_connector_limit_per_host: Optional[int] = None,
+        client_session_kwargs: Optional[Dict[str, Any]] = None,
         ca_cert_data: Optional[Union[str, bytes]] = None,
         cert_file: Optional[str]=None,
         key_file: Optional[str]=None,
@@ -409,6 +420,15 @@ def __init__(
         self.retries = retries
         """Retry configuration
         """
+        self.trace_configs = trace_configs
+        """aiohttp.TraceConfig list forwarded to ClientSession for tracing.
+        """
+        self.tcp_connector_limit_per_host = tcp_connector_limit_per_host
+        """Per-host concurrency cap forwarded to TCPConnector.
+        """
+        self.client_session_kwargs = client_session_kwargs
+        """Extra kwargs merged into aiohttp.ClientSession(**kwargs).
+        """
         # Enable client side validation
         self.client_side_validation = client_side_validation
 

samples/openapi3/client/petstore/python-aiohttp/petstore_api/rest.py

@@ -16,7 +16,7 @@
 import json
 import re
 import ssl
-from typing import Optional, Union
+from typing import Any, Dict, Optional, Union
 
 import aiohttp
 import aiohttp_retry
@@ -58,6 +58,10 @@ class RESTClientObject:
 
     def __init__(self, configuration) -> None:
 
+        # Keep a reference so factory methods (_create_pool_manager / _create_connector)
+        # and subclasses can read extension fields like trace_configs.
+        self.configuration = configuration
+
         # maxsize is number of requests to host that are allowed in parallel
         self.maxsize = configuration.connection_pool_maxsize
 
@@ -101,6 +105,40 @@ async def close(self) -> None:
         if self.retry_client is not None:
             await self.retry_client.close()
 
+    def _create_connector(self) -> aiohttp.TCPConnector:
+        """Build the TCPConnector used by the ClientSession.
+
+        Override in a subclass to customize DNS resolver, keepalive, etc.
+        """
+        kwargs: Dict[str, Any] = {
+            "limit": self.maxsize,
+            "ssl": self.ssl_context,
+        }
+        limit_per_host = getattr(self.configuration, "tcp_connector_limit_per_host", None)
+        if limit_per_host is not None:
+            kwargs["limit_per_host"] = limit_per_host
+        return aiohttp.TCPConnector(**kwargs)
+
+    def _create_pool_manager(self) -> aiohttp.ClientSession:
+        """Build the aiohttp.ClientSession used as the connection pool.
+
+        Override in a subclass to fully customize the session (e.g. attach
+        aiohttp.TraceConfig, swap json_serialize, etc.). Typed Configuration
+        fields (trace_configs / client_session_kwargs) are read via getattr
+        so older Configuration objects remain compatible.
+        """
+        kwargs: Dict[str, Any] = {
+            "connector": self._create_connector(),
+            "trust_env": True,
+        }
+        trace_configs = getattr(self.configuration, "trace_configs", None)
+        if trace_configs is not None:
+            kwargs["trace_configs"] = trace_configs
+        extra = getattr(self.configuration, "client_session_kwargs", None)
+        if extra:
+            kwargs.update(extra)
+        return aiohttp.ClientSession(**kwargs)
+
     async def request(
         self,
         method,
@@ -209,10 +247,7 @@ async def request(
 
         # https pool manager
         if self.pool_manager is None:
-            self.pool_manager = aiohttp.ClientSession(
-                connector=aiohttp.TCPConnector(limit=self.maxsize, ssl=self.ssl_context),
-                trust_env=True,
-            )
+            self.pool_manager = self._create_pool_manager()
         pool_manager = self.pool_manager
 
         if self._effective_retry_options is not None and method in ALLOW_RETRY_METHODS: