Add a `lsp_config_callback` linter option

This is the callback-based variant of the existing `lsp_config` linter
option. It serves the same purpose but can be used when more complicated
processing is needed.

`lsp_config` and `lsp_config_callback` are mutually exclusive options;
if both an given, a linter preprocessing error will be raised.

The runtime logic has been wrapped in `ale#lsp_linter#GetConfig` for
convenience, similar to `ale#lsp_linter#GetOptions`.

This also adds documentation and an `AssertLSPConfig` test function for
completeness.

autoload/ale/assert.vim

@@ -85,6 +85,14 @@ function! ale#assert#LSPOptions(expected_options) abort
     AssertEqual a:expected_options, l:initialization_options
 endfunction
 
+function! ale#assert#LSPConfig(expected_config) abort
+    let l:buffer = bufnr('')
+    let l:linter = s:GetLinter()
+    let l:config = ale#lsp_linter#GetConfig(l:buffer, l:linter)
+
+    AssertEqual a:expected_config, l:config
+endfunction
+
 function! ale#assert#LSPLanguage(expected_language) abort
     let l:buffer = bufnr('')
     let l:linter = s:GetLinter()
@@ -147,6 +155,7 @@ function! ale#assert#SetUpLinterTest(filetype, name) abort
     command! -nargs=+ AssertLinter :call ale#assert#Linter(<args>)
     command! -nargs=0 AssertLinterNotExecuted :call ale#assert#LinterNotExecuted()
     command! -nargs=+ AssertLSPOptions :call ale#assert#LSPOptions(<args>)
+    command! -nargs=+ AssertLSPConfig :call ale#assert#LSPConfig(<args>)
     command! -nargs=+ AssertLSPLanguage :call ale#assert#LSPLanguage(<args>)
     command! -nargs=+ AssertLSPProject :call ale#assert#LSPProject(<args>)
     command! -nargs=+ AssertLSPAddress :call ale#assert#LSPAddress(<args>)
@@ -172,6 +181,10 @@ function! ale#assert#TearDownLinterTest() abort
         delcommand AssertLSPOptions
     endif
 
+    if exists(':AssertLSPConfig')
+        delcommand AssertLSPConfig
+    endif
+
     if exists(':AssertLSPLanguage')
         delcommand AssertLSPLanguage
     endif

autoload/ale/linter.vim

@@ -257,7 +257,17 @@ function! ale#linter#PreProcess(filetype, linter) abort
             let l:obj.initialization_options = a:linter.initialization_options
         endif
 
-        if has_key(a:linter, 'lsp_config')
+        if has_key(a:linter, 'lsp_config_callback')
+            if has_key(a:linter, 'lsp_config')
+                throw 'Only one of `lsp_config` or `lsp_config_callback` should be set'
+            endif
+
+            let l:obj.lsp_config_callback = a:linter.lsp_config_callback
+
+            if !s:IsCallback(l:obj.lsp_config_callback)
+                throw '`lsp_config_callback` must be a callback if defined'
+            endif
+        elseif has_key(a:linter, 'lsp_config')
             if type(a:linter.lsp_config) isnot v:t_dict
                 throw '`lsp_config` must be a Dictionary'
             endif

autoload/ale/lsp_linter.vim

@@ -140,6 +140,18 @@ function! ale#lsp_linter#GetOptions(buffer, linter) abort
     return l:initialization_options
 endfunction
 
+function! ale#lsp_linter#GetConfig(buffer, linter) abort
+    let l:config = {}
+
+    if has_key(a:linter, 'lsp_config_callback')
+        let l:config = ale#util#GetFunction(a:linter.lsp_config_callback)(a:buffer)
+    elseif has_key(a:linter, 'lsp_config')
+        let l:config = a:linter.lsp_config
+    endif
+
+    return l:config
+endfunction
+
 " Given a buffer, an LSP linter, start up an LSP linter and get ready to
 " receive messages for the document.
 function! ale#lsp_linter#StartLSP(buffer, linter) abort
@@ -188,14 +200,16 @@ function! ale#lsp_linter#StartLSP(buffer, linter) abort
         call ale#lsp#MarkConnectionAsTsserver(l:conn_id)
     endif
 
-    let l:language_id = ale#util#GetFunction(a:linter.language_callback)(a:buffer)
+    let l:config = ale#lsp_linter#GetConfig(a:buffer, a:linter)
 
-    if !empty(get(a:linter, 'lsp_config'))
+    if !empty(l:config)
         " set LSP configuration options (workspace/didChangeConfiguration)
-        let l:config_message = ale#lsp#message#DidChangeConfiguration(a:buffer, a:linter.lsp_config)
+        let l:config_message = ale#lsp#message#DidChangeConfiguration(a:buffer, l:config)
         call ale#lsp#Send(l:conn_id, l:config_message)
     endif
 
+    let l:language_id = ale#util#GetFunction(a:linter.language_callback)(a:buffer)
+
     let l:details = {
     \   'buffer': a:buffer,
     \   'connection_id': l:conn_id,

doc/ale-development.txt

@@ -306,6 +306,7 @@ given the above setup are as follows.
 `AssertLinterNotExecuted`          - Check that linters will not be executed.
 `AssertLSPLanguage language`       - Check the language given to an LSP server.
 `AssertLSPOptions options_dict`    - Check the options given to an LSP server.
+`AssertLSPConfig config_dict`      - Check the config given to an LSP server.
 `AssertLSPProject project_root`    - Check the root given to an LSP server.
 `AssertLSPAddress address`         - Check the address to an LSP server.
 

doc/ale.txt

@@ -2666,6 +2666,9 @@ ale#linter#Define(filetype, linter)                       *ale#linter#Define()*
                          `initialization_options_callback` may be defined to
                          pass initialization options to the LSP.
 
+                         An optional `lsp_config` or `lsp_config_callback` may
+                         be defined to pass configuration settings to the LSP.
+
   `address_callback`       A |String| or |Funcref| for a callback function
                          accepting a buffer number. A |String| should be
                          returned with an address to connect to.
@@ -2726,6 +2729,16 @@ ale#linter#Define(filetype, linter)                       *ale#linter#Define()*
                          This can be used in place of `initialization_options`
                          when more complicated processing is needed.
 
+  `lsp_config`           A |Dictionary| of configuration settings for LSPs.
+                         This will be fed (as JSON) to the LSP in the
+                         workspace/didChangeConfiguration command.
+
+  `lsp_config_callback`  A |String| or |Funcref| for a callback function
+                         accepting a buffer number. A |Dictionary| should be
+                         returned for configuration settings to pass the LSP.
+                         This can be used in place of `lsp_config` when more
+                         complicated processing is needed.
+
   Only one of `command`, `command_callback`, or `command_chain` should be
   specified. `command_callback` is generally recommended when a command string
   needs to be generated dynamically, or any global options are used.

test/command_callback/test_elixir_ls_command_callbacks.vader

@@ -26,4 +26,5 @@ Execute(should set correct LSP values):
 
   AssertLSPLanguage 'elixir'
   AssertLSPOptions {}
+  AssertLSPConfig {}
   AssertLSPProject ale#path#Simplify(g:dir . '/mix_paths/wrapped_project')

test/command_callback/test_golangserver_command_callback.vader

@@ -56,7 +56,7 @@ Execute(should set go-langserver for go app1):
   call ale#test#SetFilename('go_paths/go1/prj1/file.go')
 
   AssertLSPLanguage 'go'
-  AssertLSPOptions {}
+  AssertLSPConfig {}
   AssertLSPProject ale#path#Simplify(g:dir . '/go_paths/go1')
 
 Execute(should set go-langserver for go app2):
@@ -64,4 +64,5 @@ Execute(should set go-langserver for go app2):
 
   AssertLSPLanguage 'go'
   AssertLSPOptions {}
+  AssertLSPConfig {}
   AssertLSPProject ale#path#Simplify(g:dir . '/go_paths/go2')

test/command_callback/test_scala_sbtserver.vader

@@ -9,11 +9,13 @@ Execute(should set sbtserver for sbt project with build.sbt):
   call ale#test#SetFilename('../scala_fixtures/valid_sbt_project/Main.scala')
   AssertLSPLanguage 'scala'
   AssertLSPOptions {}
+  AssertLSPConfig {}
   AssertLSPProject ale#path#Simplify(g:dir . 'command_callback/../scala_fixtures/valid_sbt_project')
   AssertLSPAddress '127.0.0.1:4273'
 Execute(should not set sbtserver for sbt project without build.sbt):
   call ale#test#SetFilename('../scala_fixtures/invalid_sbt_project/Main.scala')
   AssertLSPLanguage 'scala'
   AssertLSPOptions {}
+  AssertLSPConfig {}
   AssertLSPProject ''
   AssertLSPAddress '127.0.0.1:4273'

test/test_linter_defintion_processing.vader

@@ -501,6 +501,31 @@ Execute(PreProcess should throw when initialization_options_callback is not a ca
   \})
   AssertEqual '`initialization_options_callback` must be a callback if defined', g:vader_exception
 
+Execute(PreProcess should complain about using lsp_config and lsp_config_callback together):
+  let g:linter = {
+  \ 'name': 'x',
+  \ 'lsp': 'socket',
+  \ 'address_callback': 'X',
+  \ 'language': 'x',
+  \ 'project_root_callback': 'x',
+  \ 'lsp_config': 'x',
+  \ 'lsp_config_callback': 'x',
+  \}
+
+  AssertThrows call ale#linter#PreProcess('testft', g:linter)
+  AssertEqual 'Only one of `lsp_config` or `lsp_config_callback` should be set', g:vader_exception
+
+Execute(PreProcess should throw when lsp_config_callback is not a callback):
+  AssertThrows call ale#linter#PreProcess('testft', {
+  \ 'name': 'foo',
+  \ 'lsp': 'socket',
+  \ 'address_callback': 'X',
+  \ 'language': 'x',
+  \ 'project_root_callback': 'x',
+  \ 'lsp_config_callback': {},
+  \})
+  AssertEqual '`lsp_config_callback` must be a callback if defined', g:vader_exception
+
 Execute(PreProcess should accept LSP configuration options via lsp_config):
   let g:ale_lsp_configuration = {
   \ 'foo': 'bar'
@@ -517,7 +542,6 @@ Execute(PreProcess should accept LSP configuration options via lsp_config):
 
   AssertEqual {'foo': 'bar'}, ale#linter#PreProcess('testft', g:linter).lsp_config
 
-
 Execute(PreProcess should throw when lsp_config is not a Dictionary):
   AssertThrows call ale#linter#PreProcess('testft', {
   \ 'name': 'foo',
@@ -528,4 +552,3 @@ Execute(PreProcess should throw when lsp_config is not a Dictionary):
   \ 'lsp_config': 'x',
   \})
   AssertEqual '`lsp_config` must be a Dictionary', g:vader_exception
-