textDocument/documentSymbol does not respect client capabilities

[bstaletic]

Seems like the response to textDocument/documentSymbol is always hierarchical and that Omnisharp is not taking into account textDocument.documentSymbol.hierarchicalDocumentSymbolSupport client capability.

Here are the messages exchanged between my client and this server:

https://gist.github.com/bstaletic/e47462e95dcc4294048cd3ecefd3c9b6

And here's the same thing, but without O#, publishDiagnostics and logMessage:

2024-08-17 21:26:13,983 - DEBUG - TX: Sending message: b'Content-Length: 2101\r\n\r\n{"id":1,"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{"textDocument":{"codeAction":{"codeActionLiteralSupport":{"codeActionKind":{"valueSet":["","quickfix","refactor","refactor.extract","refactor.inline","refactor.rewrite","source","source.organizeImports","source.fixAll"]}},"dataSupport":true,"resolveSupport":{"properties":["edit","command"]}},"completion":{"completionItem":{"documentationFormat":["plaintext","markdown"],"resolveSupport":{"properties":["documentation","detail"]}},"completionItemKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]}},"documentSymbol":{"hierarchicalDocumentSymbolSupport":false,"labelSupport":false,"symbolKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]}},"hover":{"contentFormat":["plaintext","markdown"]},"inlay_hint":{},"semanticTokens":{"augmentSyntaxTokens":true,"formats":["relative"],"requests":{"full":{"delta":false},"range":true},"tokenModifiers":[],"tokenTypes":["namespace","type","class","enum","interface","struct","typeParameter","parameter","variable","property","enumMember","event","function","method","member","macro","keyword","modifier","comment","string","number","regexp","operator"]},"signatureHelp":{"signatureInformation":{"documentationFormat":["plaintext","markdown"],"parameterInformation":{"labelOffsetSupport":true}}},"synchronization":{"didSave":true}},"workspace":{"applyEdit":true,"didChangeWatchedFiles":{"dynamicRegistration":true},"symbol":{"symbolKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]}},"workspaceEdit":{"documentChanges":true},"workspaceFolders":true}},"initializationOptions":{},"processId":13056,"rootPath":"/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/tests/cs/testdata/testy","rootUri":"file:///home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/tests/cs/testdata/testy","workspaceFolders":[{"name":"testy","uri":"file:///home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/tests/cs/testdata/testy"}]}}'
2024-08-17 21:26:21,052 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":1,"result":{"capabilities":{"textDocumentSync":{"openClose":true,"change":1,"save":{"includeText":true}},"hoverProvider":{},"completionProvider":{"resolveProvider":true,"triggerCharacters":["."," "]},"signatureHelpProvider":{"triggerCharacters":["(",",","<","{","["]},"definitionProvider":{},"referencesProvider":{},"documentHighlightProvider":{},"documentSymbolProvider":{},"workspaceSymbolProvider":{},"codeActionProvider":{"codeActionKinds":["source.organizeImports","refactor","refactor.extract","refactor.inline"],"resolveProvider":true},"codeLensProvider":{"resolveProvider":true},"documentFormattingProvider":{},"documentRangeFormattingProvider":{},"documentOnTypeFormattingProvider":{"firstTriggerCharacter":"}","moreTriggerCharacter":[";","\\n"]},"renameProvider":{},"experimental":{},"typeDefinitionProvider":{},"implementationProvider":{},"semanticTokensProvider":{"legend":{"tokenTypes":["comment","excludedCode","identifier","keyword","controlKeyword","number","operator","operatorOverloaded","macro","string","whiteSpace","text","staticSymbol","preprocessorText","punctuation","verbatimStringLiteral","stringEscapeCharacter","class","delegateName","enum","interface","moduleName","struct","typeParameter","fieldName","enumMember","constantName","variable","parameter","method","extensionMethodName","property","event","namespace","label","xmlDocCommentAttributeName","xmlDocCommentAttributeQuotes","xmlDocCommentAttributeValue","xmlDocCommentCDataSection","xmlDocCommentComment","xmlDocCommentDelimiter","xmlDocCommentEntityReference","xmlDocCommentName","xmlDocCommentProcessingInstruction","xmlDocCommentText","xmlLiteralAttributeName","xmlLiteralAttributeQuotes","xmlLiteralAttributeValue","xmlLiteralCDataSection","xmlLiteralComment","xmlLiteralDelimiter","xmlLiteralEmbeddedExpression","xmlLiteralEntityReference","xmlLiteralName","xmlLiteralProcessingInstruction","xmlLiteralText","regexComment","regexCharacterClass","regexAnchor","regexQuantifier","regexGrouping","regexAlternation","regexText","regexSelfEscapedCharacter","regexOtherEscape"],"tokenModifiers":["static"]},"range":true,"full":{}},"foldingRangeProvider":{},"inlayHintProvider":{"resolveProvider":true},"workspace":{"workspaceFolders":{"supported":true,"changeNotifications":true},"fileOperations":{}}},"serverInfo":{"name":"OmniSharp","version":"1.39.12"}}}'
2024-08-17 21:26:21,055 - DEBUG - TX: Sending notification: b'Content-Length: 52\r\n\r\n{"jsonrpc":"2.0","method":"initialized","params":{}}'
2024-08-17 21:26:21,055 - DEBUG - TX: Sending notification: b'Content-Length: 86\r\n\r\n{"jsonrpc":"2.0","method":"workspace/didChangeConfiguration","params":{"settings":{}}}'
2024-08-17 21:26:21,057 - DEBUG - TX: Sending notification: b'Content-Length: 409\r\n\r\n{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"languageId":"cs","text":"using System;\\n\\nnamespace testy\\n{\\n\\tclass MainClass\\n\\t{\\n\\t\\tpublic static void Main (string[] args)\\n\\t\\t{\\n\\t\\t\\tint \\u4e5d = 9;\\n\\t\\t\\tConsole.\\n\\t\\t}\\n\\t}\\n}\\n","uri":"file:///home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/tests/cs/testdata/testy/Program.cs","version":1}}}'
2024-08-17 21:26:21,162 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":1,"method":"client/registerCapability","params":{"registrations":[{"id":"169f6065-a2f8-4f79-9958-fb30b0fcb862","method":"workspace/didChangeWatchedFiles","registerOptions":{"watchers":[{"globPattern":"**/*.*","kind":7}]}}]}}'
2024-08-17 21:26:21,164 - DEBUG - TX: Sending response: b'Content-Length: 38\r\n\r\n{"id":1,"jsonrpc":"2.0","result":null}'
2024-08-17 21:26:21,165 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":2,"method":"client/registerCapability","params":{"registrations":[{"id":"169f6065-a2f8-4f79-9958-fb30b0fcb862","method":"workspace/didChangeWatchedFiles","registerOptions":{"watchers":[{"globPattern":"**/*.*","kind":7}]}}]}}'
2024-08-17 21:26:21,174 - DEBUG - TX: Sending response: b'Content-Length: 38\r\n\r\n{"id":2,"jsonrpc":"2.0","result":null}'
2024-08-17 21:26:30,425 - DEBUG - TX: Sending message: b'Content-Length: 216\r\n\r\n{"id":2,"jsonrpc":"2.0","method":"textDocument/documentSymbol","params":{"textDocument":{"uri":"file:///home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/tests/cs/testdata/testy/Program.cs"}}}'
2024-08-17 21:26:30,525 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":2,"result":[{"name":"testy","kind":3,"range":{"start":{"line":2,"character":0},"end":{"line":12,"character":1}},"selectionRange":{"start":{"line":2,"character":10},"end":{"line":2,"character":15}},"children":[{"name":"MainClass","kind":5,"range":{"start":{"line":4,"character":1},"end":{"line":11,"character":2}},"selectionRange":{"start":{"line":4,"character":7},"end":{"line":4,"character":16}},"children":[{"name":"Main","kind":6,"range":{"start":{"line":6,"character":2},"end":{"line":10,"character":3}},"selectionRange":{"start":{"line":6,"character":21},"end":{"line":6,"character":25}},"children":[]}]}]}]}'

As you can see, the client sent "documentSymbol":{"hierarchicalDocumentSymbolSupport":false... in the initialize request.
However, omnisharp has still responded with a hierarchical document symbol:

[
  {
    "name": "testy",
    "kind": 3,
    "range": {
      "start": {
        "line": 2,
        "character": 0
      },
      "end": {
        "line": 12,
        "character": 1
      }
    },
    "selectionRange": {
      "start": {
        "line": 2,
        "character": 10
      },
      "end": {
        "line": 2,
        "character": 15
      }
    },
    "children": [
      {
        "name": "MainClass",
        "kind": 5,
        "range": {
          "start": {
            "line": 4,
            "character": 1
          },
          "end": {
            "line": 11,
            "character": 2
          }
        },
        "selectionRange": {
          "start": {
            "line": 4,
            "character": 7
          },
          "end": {
            "line": 4,
            "character": 16
          }
        },
        "children": [
          {
            "name": "Main",
            "kind": 6,
            "range": {
              "start": {
                "line": 6,
                "character": 2
              },
              "end": {
                "line": 10,
                "character": 3
              }
            },
            "selectionRange": {
              "start": {
                "line": 6,
                "character": 21
              },
              "end": {
                "line": 6,
                "character": 25
              }
            },
            "children": []
          }
        ]
      }
    ]
  }
]

Here's the link to the specification: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_documentSymbol
It says that DocumentSymbol[] is hierarchical, unlike SymbolInfo[].
As for the capability:

	/**
	 * The client supports hierarchical document symbols.
	 */
	hierarchicalDocumentSymbolSupport?: boolean;