[Bug] Blob trigger uses incorrect authentication method

[donheerschap]

Expected Behavior

When using identity-based connection settings it should use the managed identity auth method.

Actual Behavior

It tries to use the connection string method and fails because it tries to parse a non-existent setting.

Steps to Reproduce

1. Create identity-based connections in the environment variables, in this case: DATALAKE__queueServiceUri & DATALAKE__blobServiceUri
2. Create a blob trigger using connection="DATALAKE"
3. Create a test blob in the path defined for the blob trigger
4. It will result into erroring parsing the non-existent "DATALAKE" env variable.

If you use the AzureWebJobsStorage__accountname and set connection="AzureWebJobsStorage" without having the AzureWebJobsStorage setting it works, so it's only for custom connections which are documented here

Relevant code being tried

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "python",
    "AzureWebJobsFeatureFlags": "EnableWorkerIndexing",
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "DATALAKE__blobServiceUri": "https://REDACTED.blob.core.windows.net/",
    "DATALAKE__serviceUri": "https://REDACTED.blob.core.windows.net/",
    "DATALAKE__queueServiceUri": "https://REDACTED.queue.core.windows.net/"
  }
}

import logging
import os

import azure.functions as func
from azure.identity import DefaultAzureCredential
from azure.storage.blob import BlobClient
import azurefunctions.extensions.bindings.blob as blob

bp = func.Blueprint()

@bp.function_name(name="process_blob_weather_data")
@bp.blob_trigger(
    arg_name="sourceblob", path="bronze/weatherdata/{name}.json", connection="DATALAKE"
)
def process_blob_weather_data(sourceblob: blob.BlobClient):
    logging.info('Starting to process blob')
    logging.info(
        f"Python blob trigger function processed blob! Perms \n"
        f"Properties: {sourceblob.get_blob_properties()}\n"
        f"Blob content head: {sourceblob.download_blob().read(size=1)}"
    )
    
    logging.info('Blob processed')

Relevant log output

ContextEnabledTask exception was never retrieved
future: <ContextEnabledTask finished name='Task-8' coro=<Dispatcher._dispatch_grpc_request() done, defined at C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11\WINDOWS\X64\azure_functions_worker\dispatcher.py:263> exception=UnboundLocalError("cannot access local variable 'http_v2_enabled' where it is not associated with a value")>
Traceback (most recent call last):
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11\WINDOWS\X64\azure_functions_worker\dispatcher.py", line 565, in _handle__invocation_request  
    args[pb.name] = bindings.from_incoming_proto(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11\WINDOWS\X64\azure_functions_worker\bindings\meta.py", line 183, in from_incoming_proto       
    return deferred_bindings_decode(binding=binding,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11\WINDOWS\X64\azure_functions_worker\bindings\meta.py", line 301, in deferred_bindings_decode  
    deferred_binding_type = binding.decode(datum,
                            ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Source\InSparkSolutions\smallestAzureDataplatform\functions\.venv\Lib\site-packages\azurefunctions\extensions\bindings\blob\blobClientConverter.py", line 43, in decode
    return BlobClient(data=data).get_sdk_type()
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Source\InSparkSolutions\smallestAzureDataplatform\functions\.venv\Lib\site-packages\azurefunctions\extensions\bindings\blob\blobClient.py", line 35, in get_sdk_type
    return BlobClientSdk.from_connection_string(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Source\InSparkSolutions\smallestAzureDataplatform\functions\.venv\Lib\site-packages\azure\storage\blob\_blob_client.py", line 347, in from_connection_string        
    account_url, secondary, credential = parse_connection_str(conn_str, credential, 'blob')
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Source\InSparkSolutions\smallestAzureDataplatform\functions\.venv\Lib\site-packages\azure\storage\blob\_shared\base_client.py", line 368, in parse_connection_str   
    conn_str = conn_str.rstrip(";")
               ^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'rstrip'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11\WINDOWS\X64\azure_functions_worker\dispatcher.py", line 274, in _dispatch_grpc_request       
    resp = await request_handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11\WINDOWS\X64\azure_functions_worker\dispatcher.py", line 655, in _handle__invocation_request  
    if http_v2_enabled:
       ^^^^^^^^^^^^^^^
UnboundLocalError: cannot access local variable 'http_v2_enabled' where it is not associated with a value

requirements.txt file

azure-functions pandas requests azure-identity azure-storage-blob azurefunctions-extensions-bindings-blob

Where are you facing this problem?

Local - Core Tools

Function app name

No response

Additional Information

No response