[BUG] Empty query params are discarded #894

Investigative information

• Timestamp: 1632902318
• Function App name:
• Function name(s) (as appropriate):
• Core Tools version: 3.2.0-0 Commit hash: 5ffe001695be89a9b33cb569c875aef15938830b

Repro steps

Provide the steps required to reproduce the problem:

1. Create simple function:
   __init__.py

   import azure.functions
   
   def main(req: azure.functions.HttpRequest):
       return str(req.params)

   function.json

   {
       "scriptFile": "__init__.py",
       "bindings": [
           {
               "authLevel": "anonymous",
               "type": "httpTrigger",
               "direction": "in",
               "name": "req",
               "methods": [
                   "get",
                   "post"
               ]
           },
           {
               "type": "http",
               "direction": "out",
               "name": "$return"
           }
       ]
   }

2. Access function URL with query params ?paramwithvalue=foo&paramwithoutvalue
3. {"paramwithvalue": "foo"} is returned

Expected behavior

I would expect the HttpRequest.params to contain all query params, defaulting to either a value of None or an empty string:

{
    "paramwithvalue": "foo",
    "paramwithoutvalue": ""
}

Actual behavior

The query parameter is silently discarded:

{
    "paramwithvalue": "foo"
}

Known workarounds

The query param can be retrieved via urllib.parse.parse_qs from the HttpRequest.urlobject:

__init__.py

from urllib.parse import parse_qs, urlparse

import azure.functions

def main(req: azure.functions.HttpRequest):
    return str(parse_qs(urlparse(req.url).query, keep_blank_values=True))

This will return the full set of params:

"{'paramwithvalue': ['foo'], 'paramwithoutvalue': ['']}"

Contents of the requirements.txt file:

azure-functions==1.7.2

Related information

This seems to be an underlying issue in the protobuf implementation and was already fixed in Azure/azure-functions-language-worker-protobuf#49

• Add alternative for headers and query for RpcHttp that don't rely on "map" azure-functions-language-worker-protobuf#49
• Add nullable header / query / params for HTTP azure-functions-nodejs-worker#326
• Empty Query Parameters not coming through azure-functions-nodejs-worker#253