Add multiple language server association with syntax elements

.github/workflows/unitests.yml

@@ -12,23 +12,26 @@ jobs:
     steps:
       - name: Install packages
         run: |
-          sudo apt update
+          sudo apt-get update
           # install clangd language server
-          sudo apt install -y clangd-15
+          sudo apt-get install -y clangd-15
           # install nodejs
-          sudo apt install -y curl
+          sudo apt-get install -y curl
           curl -fsSL https://deb.nodesource.com/setup_18.x | sudo bash -
-          sudo apt install -y nodejs
+          sudo apt-get install -y nodejs
           # install the typescript language server
           sudo npm install -g typescript-language-server typescript
           # install the golang language server
-          sudo apt install -y golang
-          sudo apt install -y gopls
+          sudo apt-get install -y golang
+          sudo apt-get install -y gopls
           # install the rust language server
-          sudo apt install -y cargo rust-src
+          sudo apt-get install -y cargo rust-src
           mkdir -p ~/.local/bin
           curl -L https://github.com/rust-lang/rust-analyzer/releases/latest/download/rust-analyzer-x86_64-unknown-linux-gnu.gz | gunzip -c - > ~/.local/bin/rust-analyzer
           chmod +x ~/.local/bin/rust-analyzer
+          # install markdown language server
+          curl -L https://github.com/artempyanykh/marksman/releases/latest/download/marksman-linux-x64 -o ~/.local/bin/marksman
+          chmod +x ~/.local/bin/marksman
       - name: Setup Vim
         uses: rhysd/action-setup-vim@v1
         id: vim

autoload/lsp/buffer.vim

@@ -106,6 +106,12 @@ export def BufLspServerGet(bnr: number, feature: string = null_string): dict<any
     endif
   endfor
 
+  # The LSP is explicitly associated to a specific syntax name within the syntax stack
+  var selectedLsp = SelectLSPBySyntaxNames(possibleLSPs)
+  if (!selectedLsp->empty())
+    return selectedLsp
+  endif
+
   # Return the first LSP server that supports "feature" and doesn't have it
   # disabled
   for lspserver in possibleLSPs
@@ -191,4 +197,47 @@ export def CurbufGetServerChecked(feature: string = null_string): dict<any>
   return lspserver
 enddef
 
+# Returns the selected LSP based on the syntax names stacked under the
+# current cursor position
+def SelectLSPBySyntaxNames(possibleLSPs: list<dict<any>>): dict<any>
+  var synnameStack = util.ListSynstackNamesAtPoint(line('.'), col('.'))->reverse()
+
+  if synnameStack->empty()
+    return {}
+  endif
+
+  # Initialize variables for tracking the selected LSP and the index of the
+  # matched word
+  # The syntax word statck is revesed so the word at a lower index is deeper
+  # in the syntax stack : use it in priority
+  var synWordIdx = 1000
+  var selected = {}
+
+  for server in possibleLSPs
+    if server.syntaxAssociatedLSP->empty()
+      continue
+    endif
+
+    # Loop through each syntax name in the stack
+    for idx in range(len(synnameStack))
+      # Skip this syntax name if it's not in the list of associated syntax
+      # names for this LSP
+      if server.syntaxAssociatedLSP->index(synnameStack[idx]) < 0
+        continue
+      endif
+
+      # Update the selected LSP and the index of the matched word if the
+      # syntax name has higher priority
+      if idx < synWordIdx
+        selected = server
+        synWordIdx = idx
+	# Break out of the loop once the LSP has been selected
+        break
+      endif
+    endfor
+  endfor
+
+  return selected
+enddef
+
 # vim: tabstop=8 shiftwidth=2 softtabstop=2

autoload/lsp/lsp.vim

@@ -693,6 +693,11 @@ export def AddServer(serverList: list<dict<any>>)
       server.runUnlessSearch = []
     endif
 
+    if !server->has_key('syntaxAssociatedLSP') ||
+	server.syntaxAssociatedLSP->type() != v:t_list
+      server.syntaxAssociatedLSP = []
+    endif
+
     var lspserver: dict<any> = lserver.NewLspServer(server)
 
     var ftypes = server.filetype

autoload/lsp/lspserver.vim

@@ -1892,7 +1892,8 @@ export def NewLspServer(serverParams: dict<any>): dict<any>
     typeHierPopup: -1,
     workspaceConfig: serverParams.workspaceConfig->deepcopy(),
     workspaceSymbolPopup: -1,
-    workspaceSymbolQuery: ''
+    workspaceSymbolQuery: '',
+    syntaxAssociatedLSP: serverParams.syntaxAssociatedLSP->deepcopy(),
   }
   lspserver.logfile = $'lsp-{lspserver.name}.log'
   lspserver.errfile = $'lsp-{lspserver.name}.err'

autoload/lsp/util.vim

@@ -361,4 +361,8 @@ export def FindNearestRootDir(startDir: string, files: list<any>): string
   return sortedList[0]
 enddef
 
+export def ListSynstackNamesAtPoint(line: number, col: number): list<string>
+  return synstack(line, col)->map((_, v) => v->synIDattr('name'))
+enddef
+
 # vim: tabstop=8 shiftwidth=2 softtabstop=2

doc/lsp.txt

@@ -1900,6 +1900,44 @@ everything else: >
 		},
 	])
 <
+Language servers can also be configured to associate themselves with specific
+syntax elements. If a syntax element is detected at the current location, the
+corresponding language server will take precedence over the standard ordering.
+
+To specify a language server for a particular syntax element, use the
+`syntaxAssociatedLSP` property in the configuration object passed to
+`LspAddServer`. The value of `syntaxAssociatedLSP` should be a string or list
+of strings representing the desired syntax elements.
+>
+	vim9script
+
+	# Add two LSP configurations for handling JavaScript, TypeScript, and
+	# GraphQL files.
+	g:LspAddServer([
+		{
+			# Configuration for Typescript-language-server:
+			# Used for general purposes when working with '.js'
+			# and '.ts' files.
+			filetype: ['javascript', ''typescript'],
+			path: 'typescript-language-server',
+			args: ['--stdio']
+		},
+		{
+			# Configuration for GraphQL-language-server:
+			# Specifically bound to 'graphqlTemplateString' syntax
+			# element. Will handle requests regarding GraphQL
+			# template literals.
+			filetype: ['javascript', ''typescript', 'graphql'],
+			path: 'graphql-lsp',
+			args: ['server', '-m', 'stream'],
+			syntaxAssociatedLSP: ['graphqlTemplateString'],
+		}
+	])
+
+<
+To discover the current syntax stack and determine the appropriate value for
+`syntaxAssociatedLSP`, you can employ `LspUtilGetCurrentSynStack` command. 
+
 ==============================================================================
 17. Language Server Features			*lsp-features*
 

plugin/lsp.vim

@@ -13,6 +13,7 @@ endif
 g:loaded_lsp = true
 
 import '../autoload/lsp/options.vim'
+import '../autoload/lsp/util.vim'
 import autoload '../autoload/lsp/lsp.vim'
 
 # Set LSP plugin options from 'opts'.
@@ -105,6 +106,7 @@ command! -nargs=? -bar LspSymbolSearch lsp.SymbolSearch(<q-args>, <q-mods>)
 command! -nargs=1 -bar -complete=dir LspWorkspaceAddFolder lsp.AddWorkspaceFolder(<q-args>)
 command! -nargs=0 -bar LspWorkspaceListFolders lsp.ListWorkspaceFolders()
 command! -nargs=1 -bar -complete=dir LspWorkspaceRemoveFolder lsp.RemoveWorkspaceFolder(<q-args>)
+command! -nargs=0 -bar LspUtilGetCurrentSynStack echo util.ListSynstackNamesAtPoint(line('.'), col('.'))
 
 # Add the GUI menu entries
 if has('gui_running')

test/run_tests.sh

@@ -10,7 +10,7 @@ fi
 
 VIM_CMD="$VIMPRG -u NONE -U NONE -i NONE --noplugin -N --not-a-term"
 
-TESTS="clangd_tests.vim tsserver_tests.vim gopls_tests.vim not_lspserver_related_tests.vim markdown_tests.vim rust_tests.vim"
+TESTS="clangd_tests.vim tsserver_tests.vim gopls_tests.vim not_lspserver_related_tests.vim markdown_tests.vim rust_tests.vim syntax_stack_lsp_chooser_test.vim"
 
 RunTestsInFile() {
   testfile=$1

test/syntax_stack_lsp_chooser_test.vim

@@ -0,0 +1,68 @@
+vim9script
+
+import '../autoload/lsp/buffer.vim' as buf
+import '../autoload/lsp/util.vim' as util
+
+source common.vim
+
+g:markdown_fenced_languages = ['c']
+
+var lspServers = [
+  {
+    name: 'marksman',
+    filetype: 'markdown',
+    path: (exepath('marksman') ?? expand('~') .. '/.local/bin/marksman'),
+    args: ['server'],
+  },
+  {
+    name: 'clangd',
+    filetype: 'markdown',
+    path: (exepath('clangd-15') ?? exepath('clangd')),
+    args: ['--background-index', '--clang-tidy'],
+    syntaxAssociatedLSP: ['markdownHighlight_c', 'markdownHighlightc'],
+
+  },
+]
+call LspAddServer(lspServers)
+
+def FillDummyFile()
+  :silent edit dummy.md
+  sleep 200m
+  var lines: list<string> =<< trim END
+    # Title
+
+    ```c
+    int f1() {
+      int x;
+      int y;
+      x = 1;
+      y = 2;
+      return x + y;
+    }
+    ```
+  END
+  setline(1, lines)
+enddef
+
+def g:Test_ChoseDefaultLspIfNoSyntaxMatch()
+  FillDummyFile()
+  search('Title')
+  var selected_lsp =  buf.BufLspServerGet(bufnr(), 'hover')
+  assert_true(selected_lsp->has_key('name'))
+  assert_equal(selected_lsp.name, 'marksman')
+enddef
+
+def g:Test_ChooseCorrectLspIfSyntaxMatch()
+  FillDummyFile()
+  search('int')
+  var selected_lsp =  buf.BufLspServerGet(bufnr(), 'hover')
+  assert_true(selected_lsp->has_key('name'))
+  assert_equal(selected_lsp.name, 'clangd')
+enddef
+
+# Only here to because the test runner needs it
+def g:StartLangServer(): bool
+  return true
+enddef
+
+# vim: shiftwidth=2 softtabstop=2 noexpandtab