ApiExplorer not handling multiple routes on same action method correctly

[domaindrivendev]

Describe the bug

Given the following action method bound to multiple routes:

[HttpGet]
[Route("foo")]
[Route("bar/{id}")]
public IActionResult Get(int id = 0)

As expected, the ApiExplorer surfaces two ApiDescription instances, one for each route. However, for the first route "foo", the ApiDescription includes the id path parameter, despite the fact that it's not part of the route template. For example, here's the ApiExplorer data (serialized as json):

[
  {
    relativePath: "Test/foo",
    httpMethod: "GET",
    parameters: [
      {
        name: "id",
        source: {
          displayName: "Path",
          id: "Path",
          isGreedy: false,
          isFromRequest: true,
        },
      }
    ],
  },
  {
    relativePath: "Test/bar/{id}",
    httpMethod: "GET",
    parameters: [
      {
        name: "id",
        source: {
          displayName: "Path",
          id: "Path",
          isGreedy: false,
          isFromRequest: true,
        },
      }
    ],
  },
]

To Reproduce

> git clone git@github.com:domaindrivendev/ApiExplorerIssue.git
> cd ApiExplorerIssue
> dotnet run

Then navigate to "http://localhost:5000/apidescriptions" to see the ApiExplorer data

Further technical details

• ASP.NET Core version: 3.1

[domaindrivendev]

Here's the corresponding downstream issue that was originally created in Swashbuckle.AspNetCore:
domaindrivendev/Swashbuckle.AspNetCore#1834

[domaindrivendev]

In the meantime, if you're really stuck you could wire up an IOperationFilter (see readme) that detects this anomaly and corrects it by removing the parameter from the operation.parameters collection.

[frankracis-work]

I had the filter look at ApiDescription.ParamaterDescriptions, and if In==Path and !IsRequired, removed it from the operation.Parameters list. I don't know that this will work for every case, but it was enough for my routes.

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