Add ALEGoToImplementation (#4160)

* Add go to implementation

* Add test cases for GoToImplementation

* Add documentation for GoToImplementation

autoload/ale/definition.vim

@@ -121,6 +121,12 @@ function! s:OnReady(line, column, options, capability, linter, lsp_details) abor
             \   a:line,
             \   a:column
             \)
+        elseif a:capability is# 'implementation'
+            let l:message = ale#lsp#tsserver_message#Implementation(
+            \   l:buffer,
+            \   a:line,
+            \   a:column
+            \)
         endif
     else
         " Send a message saying the buffer has changed first, or the
@@ -134,6 +140,8 @@ function! s:OnReady(line, column, options, capability, linter, lsp_details) abor
             let l:message = ale#lsp#message#Definition(l:buffer, a:line, a:column)
         elseif a:capability is# 'typeDefinition'
             let l:message = ale#lsp#message#TypeDefinition(l:buffer, a:line, a:column)
+        elseif a:capability is# 'implementation'
+            let l:message = ale#lsp#message#Implementation(l:buffer, a:line, a:column)
         else
             " XXX: log here?
             return
@@ -175,6 +183,14 @@ function! ale#definition#GoToType(options) abort
     endfor
 endfunction
 
+function! ale#definition#GoToImpl(options) abort
+    for l:linter in ale#linter#Get(&filetype)
+        if !empty(l:linter.lsp)
+            call s:GoToLSPDefinition(l:linter, a:options, 'implementation')
+        endif
+    endfor
+endfunction
+
 function! ale#definition#GoToCommandHandler(command, ...) abort
     let l:options = {}
 
@@ -200,6 +216,8 @@ function! ale#definition#GoToCommandHandler(command, ...) abort
 
     if a:command is# 'type'
         call ale#definition#GoToType(l:options)
+    elseif a:command is# 'implementation'
+        call ale#definition#GoToImpl(l:options)
     else
         call ale#definition#GoTo(l:options)
     endif

autoload/ale/lsp.vim

@@ -44,6 +44,7 @@ function! ale#lsp#Register(executable_or_address, project, init_options) abort
         \       'completion_trigger_characters': [],
         \       'definition': 0,
         \       'typeDefinition': 0,
+        \       'implementation': 0,
         \       'symbol_search': 0,
         \       'code_actions': 0,
         \       'did_save': 0,
@@ -259,6 +260,14 @@ function! s:UpdateCapabilities(conn, capabilities) abort
         let a:conn.capabilities.typeDefinition = 1
     endif
 
+    if get(a:capabilities, 'implementationProvider') is v:true
+        let a:conn.capabilities.implementation = 1
+    endif
+
+    if type(get(a:capabilities, 'implementationProvider')) is v:t_dict
+        let a:conn.capabilities.implementation = 1
+    endif
+
     if get(a:capabilities, 'workspaceSymbolProvider') is v:true
         let a:conn.capabilities.symbol_search = 1
     endif
@@ -379,6 +388,7 @@ function! ale#lsp#MarkConnectionAsTsserver(conn_id) abort
     let l:conn.capabilities.completion_trigger_characters = ['.']
     let l:conn.capabilities.definition = 1
     let l:conn.capabilities.typeDefinition = 1
+    let l:conn.capabilities.implementation = 1
     let l:conn.capabilities.symbol_search = 1
     let l:conn.capabilities.rename = 1
     let l:conn.capabilities.filerename = 1
@@ -438,6 +448,10 @@ function! s:SendInitMessage(conn) abort
     \               'typeDefinition': {
     \                   'dynamicRegistration': v:false,
     \               },
+    \               'implementation': {
+    \                   'dynamicRegistration': v:false,
+    \                   'linkSupport': v:false,
+    \               },
     \               'publishDiagnostics': {
     \                   'relatedInformation': v:true,
     \               },

autoload/ale/lsp/message.vim

@@ -139,6 +139,15 @@ function! ale#lsp#message#TypeDefinition(buffer, line, column) abort
     \}]
 endfunction
 
+function! ale#lsp#message#Implementation(buffer, line, column) abort
+    return [0, 'textDocument/implementation', {
+    \   'textDocument': {
+    \       'uri': ale#util#ToURI(expand('#' . a:buffer . ':p')),
+    \   },
+    \   'position': {'line': a:line - 1, 'character': a:column - 1},
+    \}]
+endfunction
+
 function! ale#lsp#message#References(buffer, line, column) abort
     return [0, 'textDocument/references', {
     \   'textDocument': {

autoload/ale/lsp/tsserver_message.vim

@@ -72,6 +72,14 @@ function! ale#lsp#tsserver_message#TypeDefinition(buffer, line, column) abort
     \}]
 endfunction
 
+function! ale#lsp#tsserver_message#Implementation(buffer, line, column) abort
+    return [0, 'ts@implementation', {
+    \   'line': a:line,
+    \   'offset': a:column,
+    \   'file': expand('#' . a:buffer . ':p'),
+    \}]
+endfunction
+
 function! ale#lsp#tsserver_message#References(buffer, line, column) abort
     return [0, 'ts@references', {
     \   'line': a:line,