fix(lsp): handle multiline signature help labels #30460

runtime/doc/lsp.txt

@@ -1855,7 +1855,7 @@ signature_help({_}, {result}, {ctx}, {config})
 <
 
     Parameters: ~
-      • {result}  (`lsp.SignatureHelp`) Response from the language server
+      • {result}  (`lsp.SignatureHelp?`) Response from the language server
       • {ctx}     (`lsp.HandlerContext`) Client context
       • {config}  (`table`) Configuration table.
                   • border: (default=nil)
@@ -1973,7 +1973,7 @@ convert_signature_help_to_markdown_lines({signature_help}, {ft}, {triggers})
 
     Return (multiple): ~
         (`string[]?`) table list of lines of converted markdown.
-        (`number[]?`) table of active hl
+        (`Range4?`) table of active hl
 
     See also: ~
       • https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_signatureHelp

runtime/lua/vim/lsp/handlers.lua

@@ -462,6 +462,8 @@ M[ms.textDocument_typeDefinition] = location_handler
 --- @see # https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_implementation
 M[ms.textDocument_implementation] = location_handler
 
+local sig_help_ns = api.nvim_create_namespace('vim_lsp_signature_help')
+
 --- |lsp-handler| for the method "textDocument/signatureHelp".
 ---
 --- The active parameter is highlighted with |hl-LspSignatureActiveParameter|.
@@ -476,7 +478,7 @@ M[ms.textDocument_implementation] = location_handler
 --- ```
 ---
 ---@param _ lsp.ResponseError?
----@param result lsp.SignatureHelp  Response from the language server
+---@param result lsp.SignatureHelp? Response from the language server
 ---@param ctx lsp.HandlerContext Client context
 ---@param config table Configuration table.
 ---     - border:     (default=nil)
@@ -509,10 +511,15 @@ function M.signature_help(_, result, ctx, config)
     return
   end
   local fbuf, fwin = util.open_floating_preview(lines, 'markdown', config)
+  -- Highlight the active parameter.
   if hl then
-    -- Highlight the second line if the signature is wrapped in a Markdown code block.
-    local line = vim.startswith(lines[1], '```') and 1 or 0
-    api.nvim_buf_add_highlight(fbuf, -1, 'LspSignatureActiveParameter', line, unpack(hl))
+    vim.highlight.range(
+      fbuf,
+      sig_help_ns,
+      'LspSignatureActiveParameter',
+      { hl[1], hl[2] },
+      { hl[3], hl[4] }
+    )
   end
   return fbuf, fwin
 end

runtime/lua/vim/lsp/util.lua

@@ -781,24 +781,37 @@ function M.convert_input_to_markdown_lines(input, contents)
   return contents
 end
 
+--- Returns the line/column-based position in `contents` at the given offset.
+---
+---@param offset integer
+---@param contents string[]
+---@return { [1]: integer, [2]: integer }
+local function get_pos_from_offset(offset, contents)
+  local i = 0
+  for l, line in ipairs(contents) do
+    if offset >= i and offset < i + #line then
+      return { l - 1, offset - i + 1 }
+    else
+      i = i + #line + 1
+    end
+  end
+end
+
 --- Converts `textDocument/signatureHelp` response to markdown lines.
 ---
 ---@param signature_help lsp.SignatureHelp Response of `textDocument/SignatureHelp`
 ---@param ft string|nil filetype that will be use as the `lang` for the label markdown code block
 ---@param triggers table|nil list of trigger characters from the lsp server. used to better determine parameter offsets
 ---@return string[]|nil table list of lines of converted markdown.
----@return number[]|nil table of active hl
+---@return Range4|nil table of active hl
 ---@see https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_signatureHelp
 function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers)
-  if not signature_help.signatures then
-    return
-  end
   --The active signature. If omitted or the value lies outside the range of
   --`signatures` the value defaults to zero or is ignored if `signatures.length == 0`.
   --Whenever possible implementors should make an active decision about
   --the active signature and shouldn't rely on a default value.
   local contents = {}
-  local active_hl
+  local active_offset ---@type [integer, integer]|nil
   local active_signature = signature_help.activeSignature or 0
   -- If the activeSignature is not inside the valid range, then clip it.
   -- In 3.15 of the protocol, activeSignature was allowed to be negative
@@ -806,9 +819,6 @@ function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers
     active_signature = 0
   end
   local signature = signature_help.signatures[active_signature + 1]
-  if not signature then
-    return
-  end
   local label = signature.label
   if ft then
     -- wrap inside a code block for proper rendering
@@ -825,6 +835,8 @@ function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers
     M.convert_input_to_markdown_lines(signature.documentation, contents)
   end
   if signature.parameters and #signature.parameters > 0 then
+    -- First check if the signature has an activeParameter. If it doesn't check if the response
+    -- had that property instead. Else just default to 0.
     local active_parameter = (signature.activeParameter or signature_help.activeParameter or 0)
     if active_parameter < 0 then
       active_parameter = 0
@@ -837,7 +849,7 @@ function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers
     end
 
     local parameter = signature.parameters[active_parameter + 1]
-    if parameter then
+    local parameter_label = parameter.label
     --[=[
       --Represents a parameter of a callable-signature. A parameter can
       --have a label and a doc-comment.
@@ -856,11 +868,10 @@ function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers
         documentation?: string | MarkupContent;
       }
       --]=]
-      if parameter.label then
-        if type(parameter.label) == 'table' then
-          active_hl = parameter.label
+    if type(parameter_label) == 'table' then
+      active_offset = parameter_label
     else
-          local offset = 1
+      local offset = 1 ---@type integer|nil
       -- try to set the initial offset to the first found trigger character
       for _, t in ipairs(triggers or {}) do
         local trigger_offset = signature.label:find(t, 1, true)
@@ -874,18 +885,30 @@ function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers
           break
         end
         if p == active_parameter + 1 then
-              active_hl = { offset - 1, offset + #parameter.label - 1 }
+          active_offset = { offset - 1, offset + #parameter_label - 1 }
           break
         end
         offset = offset + #param.label + 1
       end
     end
-      end
     if parameter.documentation then
       M.convert_input_to_markdown_lines(parameter.documentation, contents)
     end
   end
+
+  local active_hl = nil
+  if active_offset then
+    active_hl = {}
+    -- Account for the start of the markdown block.
+    if ft then
+      active_offset[1], active_offset[2] =
+        active_offset[1] + #contents[1], active_offset[2] + #contents[1]
     end
+
+    list_extend(active_hl, get_pos_from_offset(active_offset[1], contents))
+    list_extend(active_hl, get_pos_from_offset(active_offset[2], contents))
+  end
+
   return contents, active_hl
 end
 

test/functional/plugin/lsp_spec.lua

@@ -3519,6 +3519,30 @@ describe('LSP', function()
       local expected = { '```cs', 'TestEntity.TestEntity()', '```', 'some doc' }
       eq(expected, result)
     end)
+
+    it('highlights active parameters in multiline signature labels', function()
+      local _, hl = exec_lua(function()
+        local signature_help = {
+          activeSignature = 0,
+          signatures = {
+            {
+              activeParameter = 1,
+              label = 'fn bar(\n    _: void,\n    _: void,\n) void',
+              parameters = {
+                { label = '_: void' },
+                { label = '_: void' },
+              },
+            },
+          },
+        }
+        return vim.lsp.util.convert_signature_help_to_markdown_lines(signature_help, 'zig', { '(' })
+      end)
+      -- Note that although the higlight positions below are 0-indexed, the 2nd parameter
+      -- corresponds to the 3rd line because the first line is the ``` from the
+      -- Markdown block.
+      local expected = { 3, 4, 3, 11 }
+      eq(expected, hl)
+    end)
   end)
 
   describe('lsp.util.get_effective_tabstop', function()