Close #3600 - Implement pull diagnostics in VimL

Implement pull diagnostics in the VimL implementation so ALE is able
to track when servers are busy checking files. Only servers that
support this feature will return diagnostics these ways.

autoload/ale/lsp.vim

@@ -47,6 +47,7 @@ function! ale#lsp#Register(executable_or_address, project, language, init_option
         \       'definition': 0,
         \       'typeDefinition': 0,
         \       'implementation': 0,
+        \       'pull_model': 0,
         \       'symbol_search': 0,
         \       'code_actions': 0,
         \       'did_save': 0,
@@ -276,6 +277,13 @@ function! ale#lsp#UpdateCapabilities(conn_id, capabilities) abort
         let l:conn.capabilities.implementation = 1
     endif
 
+    " Check if the language server supports pull model diagnostics.
+    if type(get(a:capabilities, 'diagnosticProvider')) is v:t_dict
+        if type(get(a:capabilities.diagnosticProvider, 'interFileDependencies')) is v:t_bool
+            let l:conn.capabilities.pull_model = 1
+        endif
+    endif
+
     if get(a:capabilities, 'workspaceSymbolProvider') is v:true
         let l:conn.capabilities.symbol_search = 1
     endif
@@ -486,6 +494,10 @@ function! s:SendInitMessage(conn) abort
     \                   'dynamicRegistration': v:false,
     \                   'linkSupport': v:false,
     \               },
+    \               'diagnostic': {
+    \                   'dynamicRegistration': v:true,
+    \                   'relatedDocumentSupport': v:true,
+    \               },
     \               'publishDiagnostics': {
     \                   'relatedInformation': v:true,
     \               },

autoload/ale/lsp/message.vim

@@ -200,6 +200,14 @@ function! ale#lsp#message#CodeAction(buffer, line, column, end_line, end_column,
     \}]
 endfunction
 
+function! ale#lsp#message#Diagnostic(buffer) abort
+    return [0, 'textDocument/diagnostic', {
+    \   'textDocument': {
+    \       'uri': ale#util#ToURI(expand('#' . a:buffer . ':p')),
+    \   },
+    \}]
+endfunction
+
 function! ale#lsp#message#ExecuteCommand(command, arguments) abort
     return [0, 'workspace/executeCommand', {
     \   'command': a:command,

autoload/ale/lsp/response.vim

@@ -21,11 +21,11 @@ let s:SEVERITY_WARNING = 2
 let s:SEVERITY_INFORMATION = 3
 let s:SEVERITY_HINT = 4
 
-" Parse the message for textDocument/publishDiagnostics
-function! ale#lsp#response#ReadDiagnostics(response) abort
+" Convert Diagnostic[] data from a language server to an ALE loclist.
+function! ale#lsp#response#ReadDiagnostics(diagnostics) abort
     let l:loclist = []
 
-    for l:diagnostic in a:response.params.diagnostics
+    for l:diagnostic in a:diagnostics
         let l:severity = get(l:diagnostic, 'severity', 0)
         let l:loclist_item = {
         \   'text': substitute(l:diagnostic.message, '\(\r\n\|\n\|\r\)', ' ', 'g'),

autoload/ale/lsp_linter.vim

@@ -23,6 +23,26 @@ function! ale#lsp_linter#SetLSPLinterMap(replacement_map) abort
     let s:lsp_linter_map = a:replacement_map
 endfunction
 
+" A map for tracking URIs for diagnostic request IDs
+if !has_key(s:, 'diagnostic_uri_map')
+    let s:diagnostic_uri_map = {}
+endif
+
+" For internal use only.
+function! ale#lsp_linter#ClearDiagnosticURIMap() abort
+    let s:diagnostic_uri_map = {}
+endfunction
+
+" For internal use only.
+function! ale#lsp_linter#GetDiagnosticURIMap() abort
+    return s:diagnostic_uri_map
+endfunction
+
+" Just for tests.
+function! ale#lsp_linter#SetDiagnosticURIMap(replacement_map) abort
+    let s:diagnostic_uri_map = a:replacement_map
+endfunction
+
 " Get all enabled LSP linters.
 " This list still includes linters ignored with `ale_linters_ignore`.
 "
@@ -77,14 +97,17 @@ function! s:ShouldIgnoreDiagnostics(buffer, linter) abort
     return 0
 endfunction
 
-function! s:HandleLSPDiagnostics(conn_id, response) abort
+" Handle LSP diagnostics for a given URI.
+" The special value 'unchanged' can be used for diagnostics to indicate
+" that diagnostics haven't changed since we last checked.
+function! s:HandleLSPDiagnostics(conn_id, uri, diagnostics) abort
     let l:linter = get(s:lsp_linter_map, a:conn_id)
 
     if empty(l:linter)
         return
     endif
 
-    let l:filename = ale#util#ToResource(a:response.params.uri)
+    let l:filename = ale#util#ToResource(a:uri)
     let l:escaped_name = escape(
     \   fnameescape(l:filename),
     \   has('win32') ? '^' : '^,}]'
@@ -100,9 +123,12 @@ function! s:HandleLSPDiagnostics(conn_id, response) abort
         return
     endif
 
-    let l:loclist = ale#lsp#response#ReadDiagnostics(a:response)
-
-    call ale#engine#HandleLoclist(l:linter.name, l:buffer, l:loclist, 0)
+    if a:diagnostics is# 'unchanged'
+        call ale#engine#MarkLinterInactive(l:info, l:linter)
+    else
+        let l:loclist = ale#lsp#response#ReadDiagnostics(a:diagnostics)
+        call ale#engine#HandleLoclist(l:linter.name, l:buffer, l:loclist, 0)
+    endif
 endfunction
 
 function! s:HandleTSServerDiagnostics(response, error_type) abort
@@ -204,7 +230,17 @@ function! ale#lsp_linter#HandleLSPResponse(conn_id, response) abort
 
         call s:HandleLSPErrorMessage(l:linter, a:response)
     elseif l:method is# 'textDocument/publishDiagnostics'
-        call s:HandleLSPDiagnostics(a:conn_id, a:response)
+        let l:uri = a:response.params.uri
+        let l:diagnostics = a:response.params.diagnostics
+
+        call s:HandleLSPDiagnostics(a:conn_id, l:uri, l:diagnostics)
+    elseif has_key(s:diagnostic_uri_map, get(a:response, 'id'))
+        let l:uri = remove(s:diagnostic_uri_map, a:response.id)
+        let l:diagnostics = a:response.result.kind is# 'unchanged'
+        \   ? 'unchanged'
+        \   : a:response.result.items
+
+        call s:HandleLSPDiagnostics(a:conn_id, l:uri, l:diagnostics)
     elseif l:method is# 'window/showMessage'
         call ale#lsp_window#HandleShowMessage(
         \   s:lsp_linter_map[a:conn_id].name,
@@ -530,6 +566,23 @@ function! s:CheckWithLSP(linter, details) abort
             let l:save_message = ale#lsp#message#DidSave(l:buffer, l:include_text)
             let l:notified = ale#lsp#Send(l:id, l:save_message) != 0
         endif
+
+        let l:diagnostic_request_id = 0
+
+        " If the document is updated and we can pull diagnostics, try to.
+        if ale#lsp#HasCapability(l:id, 'pull_model')
+            let l:diagnostic_message = ale#lsp#message#Diagnostic(l:buffer)
+
+            let l:diagnostic_request_id = ale#lsp#Send(l:id, l:diagnostic_message)
+        endif
+
+        " If we are going to pull diagnostics, then mark the linter as active,
+        " and remember the URI we sent the request for.
+        if l:diagnostic_request_id
+            call ale#engine#MarkLinterActive(l:info, a:linter)
+            let s:diagnostic_uri_map[l:diagnostic_request_id] =
+            \   l:diagnostic_message[2].textDocument.uri
+        endif
     endif
 endfunction