[Bug]: ALS doesn't respect SignatureHelpClientCapabilities activeParameterSupport

[brownts]

Environment

• OS and Version: Linux / Ubuntu 22.04
• IDE Version: Emacs 30
• Ada & SPARK Extension Version: 26.0.202411173

Bug Summary and Reproducer

Bug Summary:

When an LSP client does not support the SignatureInformation.activeParameter (as activeParameterSupported is missing from the SignatureHelpClientCapabilities), then the field should not be provided by the Language Server, and additionally, the SignatureHelp.activeParameter should be set correctly by the Language Server in the textDocument/signatureHelp response.

Steps to reproduce:

Using an LSP client which does not support SignatureInformation.activeParameter, trigger signature help for a subroutine on the second parameter and the Language Server will indicate an index of 0 (i.e., first parameter) for the SignatureHelp.activeParameter field of the textDocument/signatureHelp response.

Expected behavior:

When an LSP client does not support SignatureInformation.activeParameter, the Language Server should indicate the correct parameter index in the SignatureHelp.activeParameter field of the textDocument/signatureHelp response.

Configuration and Logs

[ALS.MAIN] ALS version: 26.0.202411173 () (12:51:38.786)
[ALS.MAIN] Initializing server ... (12:51:38.786)
[ALS.MAIN] GPR PATH:  (12:51:38.786)
[ALS.MAIN] PATH: /home/troy/.cargo/bin:/home/troy/bin:/home/troy/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/lib/jvm/java-10-oracle/bin:/usr/lib/jvm/java-10-oracle/db/bin (12:51:38.786)
[ALS.MAIN] Ada version used for predefined completion: ADA_2020 (12:51:38.793)
[ALS.IN] {"jsonrpc":"2.0","method":"initialize","params":{"processId":734948,"rootPath":"/home/troy/junk/gtkada_24.0.0_80c56171","clientInfo":{"name":"emacs","version":"GNU Emacs 30.0.90 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.33, cairo version 1.16.0)\n of 2024
-09-07"},"rootUri":"file:///home/troy/junk/gtkada_24.0.0_80c56171","capabilities":{"general":{"positionEncodings":["utf-32","utf-16"]},"workspace":{"workspaceEdit":{"documentChanges":true,"resourceOperations":["create","rename","delete"]},"applyEdit":true,"symbol":{"symb
olKind":{"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]}},"executeCommand":{"dynamicRegistration":false},"didChangeWatchedFiles":{"dynamicRegistration":true},"workspaceFolders":true,"configuration":true,"codeLens":{"refreshSupport":true
},"diagnostics":{"refreshSupport":false},"fileOperations":{"didCreate":false,"willCreate":false,"didRename":true,"willRename":true,"didDelete":false,"willDelete":false}},"textDocument":{"declaration":{"dynamicRegistration":true,"linkSupport":true},"definition":{"dynamicR
egistration":true,"linkSupport":true},"references":{"dynamicRegistration":true},"implementation":{"dynamicRegistration":true,"linkSupport":true},"typeDefinition":{"dynamicRegistration":true,"linkSupport":true},"synchronization":{"willSave":true,"didSave":true,"willSaveWa
itUntil":true},"documentSymbol":{"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]},"hierarchicalDocumentSymbolSupport":true},"formatting":{"dynamicRegistration":true},"rangeFormatting":{"dynamicRegistration":true},"onTypeFor
matting":{"dynamicRegistration":true},"rename":{"dynamicRegistration":true,"prepareSupport":true},"codeAction":{"dynamicRegistration":true,"isPreferredSupport":true,"codeActionLiteralSupport":{"codeActionKind":{"valueSet":["","quickfix","refactor","refactor.extract","ref
actor.inline","refactor.rewrite","source","source.organizeImports"]}},"resolveSupport":{"properties":["edit","command"]},"dataSupport":true},"completion":{"completionItem":{"snippetSupport":true,"documentationFormat":["markdown","plaintext"],"resolveAdditionalTextEditsSu
pport":true,"insertReplaceSupport":true,"deprecatedSupport":true,"resolveSupport":{"properties":["documentation","detail","additionalTextEdits","command","insertTextFormat","insertTextMode"]},"insertTextModeSupport":{"valueSet":[1,2]}},"contextSupport":true,"dynamicRegis
tration":true},"signatureHelp":{"signatureInformation":{"parameterInformation":{"labelOffsetSupport":true}},"dynamicRegistration":true},"documentLink":{"dynamicRegistration":true,"tooltipSupport":true},"hover":{"contentFormat":["markdown","plaintext"],"dynamicRegistratio
n":true},"foldingRange":{"dynamicRegistration":true},"selectionRange":{"dynamicRegistration":true},"callHierarchy":{"dynamicRegistration":false},"typeHierarchy":{"dynamicRegistration":true},"publishDiagnostics":{"relatedInformation":true,"tagSupport":{"valueSet":[1,2]},"
versionSupport":true},"diagnostic":{"dynamicRegistration":false,"relatedDocumentSupport":false},"linkedEditingRange":{"dynamicRegistration":true}},"window":{"workDoneProgress":true,"showDocument":{"support":true}}},"initializationOptions":{"projectFile":"src/gtkada.gpr",
"defaultCharset":"UTF-8"},"workDoneToken":"1"},"id":8} (12:51:38.811)
[ALS.OUT] {"jsonrpc":"2.0","id":8,"result":{"capabilities":{"textDocumentSync":2,"completionProvider":{"triggerCharacters":[".",",","'","("],"resolveProvider":true},"hoverProvider":true,"signatureHelpProvider":{"triggerCharacters":[",","("],"retriggerCharacters":["\b"]},
"declarationProvider":true,"definitionProvider":true,"typeDefinitionProvider":true,"implementationProvider":true,"referencesProvider":true,"documentHighlightProvider":true,"documentSymbolProvider":true,"codeActionProvider":{"workDoneProgress":false,"codeActionKinds":["qu
ickfix","refactor.rewrite"],"resolveProvider":false},"workspaceSymbolProvider":true,"documentFormattingProvider":true,"documentRangeFormattingProvider":true,"documentOnTypeFormattingProvider":{"firstTriggerCharacter":"\n"},"renameProvider":{"prepareProvider":true},"foldi
ngRangeProvider":true,"executeCommandProvider":{"commands":["als-other-file","als-suspend-execution","als-reload-project","als-open-project-file","als-open-log-file","als-show-dependencies","als-source-dirs","als-executables","als-mains","als-project-file","als-object-di
r","als-named-parameters","als-auto-import","als-suppress-separate","als-refactor-extract-subprogram","als-refactor-introduce-parameter","als-refactor-pull_up_declaration","als-refactor-replace-type","als-refactor-sort_dependencies","als-refactor-add-parameters","als-ref
actor-remove-parameters","als-refactor-move-parameter","als-refactor-change-parameter-mode","als-refactor-change_parameters_type","als-refactor-change_parameters_default_value"]},"callHierarchyProvider":true,"semanticTokensProvider":{"legend":{"tokenTypes":[],"tokenModif
iers":[]},"range":true,"full":true},"typeHierarchyProvider":true,"workspace":{},"alsReferenceKinds":["reference","access","write","call","dispatching call","parent","child","overriding"]}}} (12:51:39.139)
[ALS.OUT] {"jsonrpc":"2.0","method":"window/logMessage","params":{"type":4,"message":"Log directory is /home/troy/.als/ada_ls_log.2024-12-16T125138.log"}} (12:51:39.139)
[ALS.IN] {"jsonrpc":"2.0","method":"initialized","params":{}} (12:51:39.219)

...

[ALS.IN] {"jsonrpc":"2.0","method":"textDocument/signatureHelp","params":{"textDocument":{"uri":"file:///home/troy/junk/gtkada_24.0.0_80c56171/src/glib.adb"},"position":{"line":102,"character":38}},"id":74} (12:52:03.045)
[ALS.OUT] {"jsonrpc":"2.0","id":74,"result":{"signatures":[{"label":"function Internal (Name : String; Thing : String) return GType","documentation":"","parameters":[{"label":"Name"},{"label":"Thing"}],"activeParameter":1}],"activeSignature":0,"activeParameter":0}} (12:52:03.047)

Other VS Code Extensions

No response

Additional context

No response

[eliericha]

Hello @brownts ,

Thank you for reporting this, we will look into it.