lsp-ui doesn't show pop-up for MarkedString[] by default

[niontrix]

Hey folks!

I have an issue with lsp-ui not showing a pop-up on hover if the LSP sends its response as MarkedString[] instead of MarkedString or just a plain old string.
My example LSP send its hover response like this:

[Trace - 01:04:47 ] Received response 'textDocument/hover - (8)' in 10ms.
Result: {
  "contents": [
    {
      "value": "File: file:///home/someuser/diy-language-server/README.md, Characters: 302",
      "language": "markdown"
    }
  ]
}

Now, I found the variable lsp-ui-doc-include-signature which, when set to t, makes lsp-ui show the pop-up.
My questions now are:
Shouldn't this be the default behavior of lsp-ui? And what does this variable really mean / is used for? Why was it designed that way?

Thanks in advance!

KR, niontrix

Edit: The specific problem I have is with nimlangserver, which always returns its hover responses as MarkedString[] regardless if the symbol being hovered on actually includes further documentation or not. Is this the proper way to do things? I could not find any specific rules in the LSP spec about that.

[niontrix]

I have created a PR that somewhat resolves the issue. 784