Support custom LSP notifications

Allow to send custom notification mesages, that expect no response from
the server.

3 files changed, 74 insertions, 32 deletions

diff --git a/autoload/ale/lsp_linter.vim b/autoload/ale/lsp_linter.vim
index 60a93504..190a16b4 100644
--- a/autoload/ale/lsp_linter.vim
+++ b/autoload/ale/lsp_linter.vim
@@ -8,8 +8,8 @@ if !has_key(s:, 'lsp_linter_map')
     let s:lsp_linter_map = {}
 endif
 
-" A Dictionary to track one-shot callbacks for custom LSP requests
-let s:custom_callbacks_map = get(s:, 'custom_callbacks_map', {})
+" A Dictionary to track one-shot handlers for custom LSP requests
+let s:custom_handlers_map = get(s:, 'custom_handlers_map', {})
 
 " Check if diagnostics for a particular linter should be ignored.
 function! s:ShouldIgnore(buffer, linter_name) abort
@@ -410,7 +410,7 @@ endfunction
 " Clear LSP linter data for the linting engine.
 function! ale#lsp_linter#ClearLSPData() abort
     let s:lsp_linter_map = {}
-    let s:custom_callbacks_map = {}
+    let s:custom_handlers_map = {}
 endfunction
 
 " Just for tests.
@@ -420,24 +420,25 @@ endfunction
 
 function! s:HandleLSPResponseToCustomRequests(conn_id, response) abort
     if has_key(a:response, 'id')
-    \&& has_key(s:custom_callbacks_map, a:response.id)
-        let l:Callback = remove(s:custom_callbacks_map, a:response.id)
-        call l:Callback(a:response)
+    \&& has_key(s:custom_handlers_map, a:response.id)
+        let l:Handler = remove(s:custom_handlers_map, a:response.id)
+        call l:Handler(a:response)
     endif
 endfunction
 
-function! s:OnReadyForCustomRequests(message, Callback, linter, lsp_details) abort
+function! s:OnReadyForCustomRequests(args, linter, lsp_details) abort
     let l:id = a:lsp_details.connection_id
-    let l:Callback = function('s:HandleLSPResponseToCustomRequests')
+    let l:request_id = ale#lsp#Send(l:id, a:args.message)
 
-    call ale#lsp#RegisterCallback(l:id, l:Callback)
-
-    let l:request_id = ale#lsp#Send(l:id, a:message)
-    let s:custom_callbacks_map[l:request_id] = a:Callback
+    if l:request_id > 0 && has_key(a:args, 'handler')
+        let l:Callback = function('s:HandleLSPResponseToCustomRequests')
+        call ale#lsp#RegisterCallback(l:id, l:Callback)
+        let s:custom_handlers_map[l:request_id] = a:args.handler
+    endif
 endfunction
 
 " Send a custom request to an LSP linter.
-function! ale#lsp_linter#SendRequest(buffer, linter_name, method, parameters, Callback) abort
+function! ale#lsp_linter#SendRequest(buffer, linter_name, message, ...) abort
     let l:filetype = ale#linter#ResolveFiletype(getbufvar(a:buffer, '&filetype'))
     let l:linter_list = ale#linter#GetAll(l:filetype)
     let l:linter_list = filter(l:linter_list, {_, v -> v.name is# a:linter_name})
@@ -452,8 +453,14 @@ function! ale#lsp_linter#SendRequest(buffer, linter_name, method, parameters, Ca
         throw 'Linter "' . a:linter_name . '" does not support LSP!'
     endif
 
-    let l:message = [0, a:method, a:parameters]
-    let l:Callback = function('s:OnReadyForCustomRequests', [l:message, a:Callback])
+    let l:is_notification = a:message[0]
+    let l:callback_args = {'message': a:message}
+
+    if !l:is_notification && a:0
+        let l:callback_args.handler = a:1
+    endif
+
+    let l:Callback = function('s:OnReadyForCustomRequests', [l:callback_args])
 
     return ale#lsp_linter#StartLSP(a:buffer, l:linter, l:Callback)
 endfunction
diff --git a/doc/ale.txt b/doc/ale.txt
index f0c0a468..f0820be6 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -3192,18 +3192,30 @@ ale#linter#PreventLoading(filetype)               *ale#linter#PreventLoading()*
   similar to prevent ALE from loading linters.
 
 
-ale#lsp_linter#SendRequest(buffer, linter_name, method, parameters, Callback)
+ale#lsp_linter#SendRequest(buffer, linter_name, message, [Handler])
                                                  *ale#lsp_linter#SendRequest()*
 
-  Send a custom request to an LSP linter.
+  Send a custom request to an LSP linter. The arguments are defined as
+  follows:
 
-  `buffer` must be a valid buffer number, and `linter_name` is a |String|
-  identifying an LSP linter that is available and enabled for the |filetype|
-  of `buffer`. `method` is a |String| identifying an LSP method supported by
-  `linter`, while `parameters` is a |dictionary| of LSP parameters applicable
-  to `method`. `Callback` is a |Funcref| that is called when a response to the
-  request is received, and takes as unique argument a dictionary representing
-  the response to the request obtained from the server.
+  `buffer`       A valid buffer number.
+
+  `linter_name`  A |String| identifying an LSP linter that is available and
+                 enabled for the |filetype| of `buffer`.
+
+  `message`      A |List| in the form `[is_notification, method, parameters]`,
+                 containing three elements:
+                 `is_notification` - an |Integer| that has value 1 if the
+                   request is a notification, 0 otherwise;
+                 `methdod` - a |String|, identifying an LSP method supported
+                   by `linter`;
+                 `parameters` - a |dictionary| of LSP parameters that are
+                   applicable to `method`.
+
+  `Handler`      Optional argument, meaningful only when `message[0]` is 0.
+                 A |Funcref| that is called when a response to the request is
+                 received, and takes as unique argument a dictionary
+                 representing the response obtained from the server.
 
 
 ale#other_source#ShowResults(buffer, linter_name, loclist)
diff --git a/test/lsp/test_lsp_custom_request.vader b/test/lsp/test_lsp_custom_request.vader
index f50a4cf2..04f044af 100644
--- a/test/lsp/test_lsp_custom_request.vader
+++ b/test/lsp/test_lsp_custom_request.vader
@@ -4,12 +4,12 @@ Before:
   runtime autoload/ale/lsp_linter.vim
 
   let g:address = 'ccls_address'
-  let g:callback_result = 0
   let g:conn_id = -1
   let g:executable = 'ccls'
   let g:executable_or_address = ''
   let g:linter_name = 'ccls'
   let g:magic_number = 42
+  let g:no_result = 0
   let g:message_list = []
   let g:message_id = 1
   let g:method = '$ccls/call'
@@ -30,6 +30,8 @@ Before:
   \   'command': '%e'
   \ }]
 
+  let g:callback_result = g:no_result
+
   " Encode dictionary to jsonrpc
   function! Encode(obj) abort
     let l:body = json_encode(a:obj)
@@ -69,16 +71,15 @@ Before:
   endfunction
 
   " Code for a test case
-  function! TestCase() abort
+  function! TestCase(is_notification) abort
     " Test sending a custom request
     let g:return_value = ale#lsp_linter#SendRequest(
     \  bufnr('%'),
     \  g:linter_name,
-    \  g:method,
-    \  g:parameters,
+    \  [a:is_notification, g:method, g:parameters],
     \  function('Callback'))
 
-    Assert index(g:message_list, [0, g:method, g:parameters]) >= 0
+    Assert index(g:message_list, [a:is_notification, g:method, g:parameters]) >= 0
 
     " Mock an incoming response to the request
     let g:response = Encode({
@@ -89,7 +90,7 @@ Before:
     call ale#lsp#HandleMessage(g:conn_id, g:response)
 
     AssertEqual
-    \ g:magic_number,
+    \ a:is_notification ? g:no_result : g:magic_number,
     \ g:callback_result
   endfunction
 
@@ -101,11 +102,13 @@ After:
   unlet! g:callback_result
   unlet! g:conn_id
   unlet! g:executable
+  unlet! g:is_notification
   unlet! g:linter_name
   unlet! g:magic_number
   unlet! g:message_list
   unlet! g:message_id
   unlet! g:method
+  unlet! g:no_result
   unlet! g:parameters
   unlet! g:project_root
   unlet! g:response
@@ -124,13 +127,33 @@ Execute(Test custom request to server identified by executable):
   let g:executable_or_address = g:executable
   let g:linter_list[0].executable = {b -> g:executable}
   let g:linter_list[0].lsp = 'stdio'
+  let g:is_notification = 0
+
+  call TestCase(g:is_notification)
+
+Given cpp(Empty cpp file):
+Execute(Test custom notification to server identified by executable):
+  let g:executable_or_address = g:executable
+  let g:linter_list[0].executable = {b -> g:executable}
+  let g:linter_list[0].lsp = 'stdio'
+  let g:is_notification = 1
 
-  call TestCase()
+  call TestCase(g:is_notification)
 
 Given cpp(Empty cpp file):
 Execute(Test custom request to server identified by address):
   let g:executable_or_address = g:address
   let g:linter_list[0].address = {b -> g:address}
   let g:linter_list[0].lsp = 'socket'
+  let g:is_notification = 0
+
+  call TestCase(g:is_notification)
+
+Given cpp(Empty cpp file):
+Execute(Test custom notification to server identified by address):
+  let g:executable_or_address = g:address
+  let g:linter_list[0].address = {b -> g:address}
+  let g:linter_list[0].lsp = 'socket'
+  let g:is_notification = 1
 
-  call TestCase()
+  call TestCase(g:is_notification)