diff --git a/ale_linters/php/langserver.vim b/ale_linters/php/langserver.vim
new file mode 100644
index 00000000..8dad5ac7
--- /dev/null
+++ b/ale_linters/php/langserver.vim
@@ -0,0 +1,38 @@
+" Author: Eric Stern <eric@ericstern.com>
+" Description: PHP Language server integration for ALE
+
+" This linter is disabled for now.
+finish
+
+call ale#Set('php_langserver_executable', 'php-language-server.php')
+call ale#Set('php_langserver_config_path', '')
+call ale#Set('php_langserver_use_global', 0)
+
+function! ale_linters#php#langserver#GetExecutable(buffer) abort
+    return ale#node#FindExecutable(a:buffer, 'php_langserver', [
+    \   'vendor/bin/php-language-server.php',
+    \])
+endfunction
+
+function! ale_linters#php#langserver#GetCommand(buffer) abort
+    return 'php ' . ale_linters#php#langserver#GetExecutable(a:buffer)
+endfunction
+
+function! ale_linters#php#langserver#GetLanguage(buffer) abort
+    return 'php'
+endfunction
+
+function! ale_linters#php#langserver#GetProjectRoot(buffer) abort
+    let l:git_path = ale#path#FindNearestDirectory(a:buffer, '.git')
+
+    return !empty(l:git_path) ? fnamemodify(l:git_path, ':h') : ''
+endfunction
+
+call ale#linter#Define('php', {
+\   'name': 'langserver',
+\   'lsp': 'stdio',
+\   'executable_callback': 'ale_linters#php#langserver#GetExecutable',
+\   'command_callback': 'ale_linters#php#langserver#GetCommand',
+\   'language_callback': 'ale_linters#php#langserver#GetLanguage',
+\   'project_root_callback': 'ale_linters#php#langserver#GetProjectRoot',
+\})
diff --git a/ale_linters/typescript/tsserver.vim b/ale_linters/typescript/tsserver.vim
index 465e80c7..7a155bd9 100644
--- a/ale_linters/typescript/tsserver.vim
+++ b/ale_linters/typescript/tsserver.vim
@@ -5,6 +5,15 @@ call ale#Set('typescript_tsserver_executable', 'tsserver')
 call ale#Set('typescript_tsserver_config_path', '')
 call ale#Set('typescript_tsserver_use_global', 0)
 
+" These functions need to be defined just to comply with the API for LSP.
+function! ale_linters#typescript#tsserver#GetProjectRoot(buffer) abort
+    return ''
+endfunction
+
+function! ale_linters#typescript#tsserver#GetLanguage(buffer) abort
+    return ''
+endfunction
+
 function! ale_linters#typescript#tsserver#GetExecutable(buffer) abort
     return ale#node#FindExecutable(a:buffer, 'typescript_tsserver', [
     \   'node_modules/.bin/tsserver',
@@ -16,4 +25,6 @@ call ale#linter#Define('typescript', {
 \   'lsp': 'tsserver',
 \   'executable_callback': 'ale_linters#typescript#tsserver#GetExecutable',
 \   'command_callback': 'ale_linters#typescript#tsserver#GetExecutable',
+\   'project_root_callback': 'ale_linters#typescript#tsserver#GetProjectRoot',
+\   'language_callback': 'ale_linters#typescript#tsserver#GetLanguage',
 \})
diff --git a/autoload/ale/completion.vim b/autoload/ale/completion.vim
index 334e2570..214891fb 100644
--- a/autoload/ale/completion.vim
+++ b/autoload/ale/completion.vim
@@ -203,41 +203,29 @@ function! s:HandleTSServerLSPResponse(response) abort
     endif
 endfunction
 
-function! s:GetCompletionsForTSServer(linter) abort
+function! s:GetLSPCompletions(linter) abort
     let l:buffer = bufnr('')
-    let l:executable = ale#linter#GetExecutable(l:buffer, a:linter)
-    let l:command = ale#job#PrepareCommand(
-    \ ale#linter#GetCommand(l:buffer, a:linter),
-    \)
-    let l:id = ale#lsp#StartProgram(
-    \   l:executable,
-    \   l:command,
+    let l:lsp_details = ale#linter#StartLSP(
+    \   l:buffer,
+    \   a:linter,
     \   function('s:HandleTSServerLSPResponse'),
     \)
 
-    if !l:id
-        if g:ale_history_enabled
-            call ale#history#Add(l:buffer, 'failed', l:id, l:command)
-        endif
+    if empty(l:lsp_details)
+        return 0
     endif
 
-    if ale#lsp#OpenTSServerDocumentIfNeeded(l:id, l:buffer)
-        if g:ale_history_enabled
-            call ale#history#Add(l:buffer, 'started', l:id, l:command)
-        endif
-    endif
+    let l:id = l:lsp_details.connection_id
+    let l:command = l:lsp_details.command
+    let l:root = l:lsp_details.project_root
 
-    call ale#lsp#Send(l:id, ale#lsp#tsserver_message#Change(l:buffer))
-
-    let l:request_id = ale#lsp#Send(
-    \   l:id,
-    \   ale#lsp#tsserver_message#Completions(
-    \       l:buffer,
-    \       b:ale_completion_info.line,
-    \       b:ale_completion_info.column,
-    \       b:ale_completion_info.prefix,
-    \   ),
+    let l:message = ale#lsp#tsserver_message#Completions(
+    \   l:buffer,
+    \   b:ale_completion_info.line,
+    \   b:ale_completion_info.column,
+    \   b:ale_completion_info.prefix,
     \)
+    let l:request_id = ale#lsp#Send(l:id, l:message, l:root)
 
     if l:request_id
         let b:ale_completion_info.conn_id = l:id
@@ -268,7 +256,7 @@ function! ale#completion#GetCompletions() abort
 
     for l:linter in ale#linter#Get(&filetype)
         if l:linter.lsp ==# 'tsserver'
-            call s:GetCompletionsForTSServer(l:linter)
+            call s:GetLSPCompletions(l:linter)
         endif
     endfor
 endfunction
diff --git a/autoload/ale/engine.vim b/autoload/ale/engine.vim
index 60cdf489..1ffdf443 100644
--- a/autoload/ale/engine.vim
+++ b/autoload/ale/engine.vim
@@ -31,13 +31,15 @@ endfunction
 
 function! ale#engine#InitBufferInfo(buffer) abort
     if !has_key(g:ale_buffer_info, a:buffer)
-        " job_list will hold the list of jobs
+        " job_list will hold the list of job IDs
+        " active_linter_list will hold the list of active linter names
         " loclist holds the loclist items after all jobs have completed.
         " temporary_file_list holds temporary files to be cleaned up
         " temporary_directory_list holds temporary directories to be cleaned up
         " history holds a list of previously run commands for this buffer
         let g:ale_buffer_info[a:buffer] = {
         \   'job_list': [],
+        \   'active_linter_list': [],
         \   'loclist': [],
         \   'temporary_file_list': [],
         \   'temporary_directory_list': [],
@@ -114,6 +116,16 @@ function! s:GatherOutput(job_id, line) abort
 endfunction
 
 function! s:HandleLoclist(linter_name, buffer, loclist) abort
+    let l:buffer_info = get(g:ale_buffer_info, a:buffer, {})
+
+    if empty(l:buffer_info)
+        return
+    endif
+
+    " Remove this linter from the list of active linters.
+    " This may have already been done when the job exits.
+    call filter(l:buffer_info.active_linter_list, 'v:val !=# a:linter_name')
+
     " Make some adjustments to the loclists to fix common problems, and also
     " to set default values for loclist items.
     let l:linter_loclist = ale#engine#FixLocList(a:buffer, a:linter_name, a:loclist)
@@ -154,6 +166,7 @@ function! s:HandleExit(job_id, exit_code) abort
     call ale#job#Stop(a:job_id)
     call remove(s:job_info_map, a:job_id)
     call filter(g:ale_buffer_info[l:buffer].job_list, 'v:val !=# a:job_id')
+    call filter(g:ale_buffer_info[l:buffer].active_linter_list, 'v:val !=# l:linter.name')
 
     " Stop here if we land in the handle for a job completing if we're in
     " a sandbox.
@@ -180,29 +193,32 @@ function! s:HandleExit(job_id, exit_code) abort
     call s:HandleLoclist(l:linter.name, l:buffer, l:loclist)
 endfunction
 
-function! s:HandleLSPResponse(response) abort
-    let l:is_diag_response = get(a:response, 'type', '') ==# 'event'
-    \   && get(a:response, 'event', '') ==# 'semanticDiag'
+function! s:HandleLSPDiagnostics(response) abort
+    let l:filename = ale#path#FromURI(a:response.params.uri)
+    let l:buffer = bufnr(l:filename)
+    let l:loclist = ale#lsp#response#ReadDiagnostics(a:response)
 
-    if !l:is_diag_response
-        return
-    endif
+    call s:HandleLoclist('langserver', l:buffer, l:loclist)
+endfunction
 
+function! s:HandleTSServerDiagnostics(response) abort
     let l:buffer = bufnr(a:response.body.file)
-
-    let l:info = get(g:ale_buffer_info, l:buffer, {})
-
-    if empty(l:info)
-        return
-    endif
-
-    let l:info.waiting_for_tsserver = 0
-
     let l:loclist = ale#lsp#response#ReadTSServerDiagnostics(a:response)
 
     call s:HandleLoclist('tsserver', l:buffer, l:loclist)
 endfunction
 
+function! s:HandleLSPResponse(response) abort
+    let l:method = get(a:response, 'method', '')
+
+    if l:method ==# 'textDocument/publishDiagnostics'
+        call s:HandleLSPDiagnostics(a:response)
+    elseif get(a:response, 'type', '') ==# 'event'
+    \&& get(a:response, 'event', '') ==# 'semanticDiag'
+        call s:HandleTSServerDiagnostics(a:response)
+    endif
+endfunction
+
 function! ale#engine#SetResults(buffer, loclist) abort
     let l:linting_is_done = !ale#engine#IsCheckingBuffer(a:buffer)
 
@@ -430,6 +446,7 @@ function! s:RunJob(options) abort
     if l:job_id
         " Add the job to the list of jobs, so we can track them.
         call add(g:ale_buffer_info[l:buffer].job_list, l:job_id)
+        call add(g:ale_buffer_info[l:buffer].active_linter_list, l:linter.name)
 
         let l:status = 'started'
         " Store the ID for the job in the map to read back again.
@@ -555,41 +572,27 @@ function! s:StopCurrentJobs(buffer, include_lint_file_jobs) abort
     let l:info.job_list = l:new_job_list
 endfunction
 
-function! s:CheckWithTSServer(buffer, linter, executable) abort
-    let l:info = g:ale_buffer_info[a:buffer]
-
-    let l:command = ale#job#PrepareCommand(
-    \ ale#linter#GetCommand(a:buffer, a:linter),
-    \)
-    let l:id = ale#lsp#StartProgram(
-    \   a:executable,
-    \   l:command,
+function! s:CheckWithLSP(buffer, linter) abort
+    let l:lsp_details = ale#linter#StartLSP(
+    \   a:buffer,
+    \   a:linter,
     \   function('s:HandleLSPResponse'),
     \)
 
-    if !l:id
-        if g:ale_history_enabled
-            call ale#history#Add(a:buffer, 'failed', l:id, l:command)
-        endif
-
+    if empty(l:lsp_details)
         return 0
     endif
 
-    if ale#lsp#OpenTSServerDocumentIfNeeded(l:id, a:buffer)
-        if g:ale_history_enabled
-            call ale#history#Add(a:buffer, 'started', l:id, l:command)
-        endif
-    endif
+    let l:id = l:lsp_details.connection_id
+    let l:root = l:lsp_details.project_root
 
-    call ale#lsp#Send(l:id, ale#lsp#tsserver_message#Change(a:buffer))
-
-    let l:request_id = ale#lsp#Send(
-    \   l:id,
-    \   ale#lsp#tsserver_message#Geterr(a:buffer),
-    \)
+    let l:change_message = a:linter.lsp ==# 'tsserver'
+    \   ? ale#lsp#tsserver_message#Geterr(a:buffer)
+    \   : ale#lsp#message#DidChange(a:buffer)
+    let l:request_id = ale#lsp#Send(l:id, l:change_message, l:root)
 
     if l:request_id != 0
-        let l:info.waiting_for_tsserver = 1
+        call add(g:ale_buffer_info[a:buffer].active_linter_list, a:linter.name)
     endif
 
     return l:request_id != 0
@@ -614,15 +617,12 @@ endfunction
 "
 " Returns 1 if the linter was successfully run.
 function! s:RunLinter(buffer, linter) abort
-    if empty(a:linter.lsp) || a:linter.lsp ==# 'tsserver'
+    if !empty(a:linter.lsp) || a:linter.lsp ==# 'tsserver'
+        return s:CheckWithLSP(a:buffer, a:linter)
+    else
         let l:executable = ale#linter#GetExecutable(a:buffer, a:linter)
 
-        " Run this program if it can be executed.
         if s:IsExecutable(l:executable)
-            if a:linter.lsp ==# 'tsserver'
-                return s:CheckWithTSServer(a:buffer, a:linter, l:executable)
-            endif
-
             return s:InvokeChain(a:buffer, a:linter, 0, [])
         endif
     endif
diff --git a/autoload/ale/job.vim b/autoload/ale/job.vim
index 93f28824..63e42f7b 100644
--- a/autoload/ale/job.vim
+++ b/autoload/ale/job.vim
@@ -199,6 +199,10 @@ function! ale#job#Start(command, options) abort
     let l:job_info = copy(a:options)
     let l:job_options = {}
 
+    if exists('*ch_logfile')
+        call ch_logfile(expand('~/channel.log'), 'a')
+    endif
+
     if has('nvim')
         if has_key(a:options, 'out_cb')
             let l:job_options.on_stdout = function('s:NeoVimCallback')
diff --git a/autoload/ale/linter.vim b/autoload/ale/linter.vim
index 1c99a0cc..0af42af9 100644
--- a/autoload/ale/linter.vim
+++ b/autoload/ale/linter.vim
@@ -62,6 +62,7 @@ function! ale#linter#PreProcess(linter) abort
     let l:needs_address = l:obj.lsp ==# 'socket'
     let l:needs_executable = l:obj.lsp !=# 'socket'
     let l:needs_command = l:obj.lsp !=# 'socket'
+    let l:needs_lsp_details = !empty(l:obj.lsp)
 
     if empty(l:obj.lsp)
         let l:obj.callback = get(a:linter, 'callback')
@@ -176,6 +177,20 @@ function! ale#linter#PreProcess(linter) abort
         throw '`address_callback` must be defined for getting the LSP address'
     endif
 
+    if l:needs_lsp_details
+        let l:obj.language_callback = get(a:linter, 'language_callback')
+
+        if !s:IsCallback(l:obj.language_callback)
+            throw '`language_callback` must be a callback for LSP linters'
+        endif
+
+        let l:obj.project_root_callback = get(a:linter, 'project_root_callback')
+
+        if !s:IsCallback(l:obj.project_root_callback)
+            throw '`project_root_callback` must be a callback for LSP linters'
+        endif
+    endif
+
     let l:obj.output_stream = get(a:linter, 'output_stream', 'stdout')
 
     if type(l:obj.output_stream) != type('')
@@ -346,3 +361,72 @@ function! ale#linter#GetCommand(buffer, linter) abort
     \   ? ale#util#GetFunction(a:linter.command_callback)(a:buffer)
     \   : a:linter.command
 endfunction
+
+" Given a buffer and linter, get the address for connecting to the server.
+function! ale#linter#GetAddress(buffer, linter) abort
+    return has_key(a:linter, 'address_callback')
+    \   ? ale#util#GetFunction(a:linter.address_callback)(a:buffer)
+    \   : a:linter.address
+endfunction
+
+" Given a buffer, an LSP linter, and a callback to register for handling
+" messages, start up an LSP linter and get ready to receive errors or
+" completions.
+function! ale#linter#StartLSP(buffer, linter, callback) abort
+    let l:command = ''
+    let l:address = ''
+    let l:root = ale#util#GetFunction(a:linter.project_root_callback)(a:buffer)
+
+    if a:linter.lsp ==# 'socket'
+        let l:address = ale#linter#GetAddress(a:buffer, a:linter)
+        let l:conn_id = ale#lsp#ConnectToAddress(
+        \   l:address,
+        \   l:root,
+        \   a:callback,
+        \)
+    else
+        let l:executable = ale#linter#GetExecutable(a:buffer, a:linter)
+
+        if !executable(l:executable)
+            return {}
+        endif
+
+        let l:command = ale#job#PrepareCommand(
+        \   ale#linter#GetCommand(a:buffer, a:linter),
+        \)
+        let l:conn_id = ale#lsp#StartProgram(
+        \   l:executable,
+        \   l:command,
+        \   l:root,
+        \   a:callback,
+        \)
+    endif
+
+    let l:language_id = ale#util#GetFunction(a:linter.language_callback)(a:buffer)
+
+    if !l:conn_id
+        if g:ale_history_enabled && !empty(l:command)
+            call ale#history#Add(a:buffer, 'failed', l:conn_id, l:command)
+        endif
+
+        return {}
+    endif
+
+    if ale#lsp#OpenDocumentIfNeeded(l:conn_id, a:buffer, l:root, l:language_id)
+        if g:ale_history_enabled && !empty(l:command)
+            call ale#history#Add(a:buffer, 'started', l:conn_id, l:command)
+        endif
+    endif
+
+    " The change message needs to be sent for tsserver before doing anything.
+    if a:linter.lsp ==# 'tsserver'
+        call ale#lsp#Send(l:conn_id, ale#lsp#tsserver_message#Change(a:buffer))
+    endif
+
+    return {
+    \   'connection_id': l:conn_id,
+    \   'command': l:command,
+    \   'project_root': l:root,
+    \   'language_id': l:language_id,
+    \}
+endfunction
diff --git a/autoload/ale/lsp.vim b/autoload/ale/lsp.vim
index 083a27ec..2c9b2990 100644
--- a/autoload/ale/lsp.vim
+++ b/autoload/ale/lsp.vim
@@ -11,10 +11,13 @@ function! s:NewConnection() abort
     " data: The message data received so far.
     " executable: An executable only set for program connections.
     " open_documents: A list of buffers we told the server we opened.
+    " callback_list: A list of callbacks for handling LSP responses.
     let l:conn = {
     \   'id': '',
     \   'data': '',
+    \   'projects': {},
     \   'open_documents': [],
+    \   'callback_list': [],
     \}
 
     call add(s:connections, l:conn)
@@ -141,6 +144,35 @@ function! ale#lsp#ReadMessageData(data) abort
     return [l:remainder, l:response_list]
 endfunction
 
+function! s:FindProjectWithInitRequestID(conn, init_request_id) abort
+    for l:project_root in keys(a:conn.projects)
+        let l:project = a:conn.projects[l:project_root]
+
+        if l:project.init_request_id == a:init_request_id
+            return l:project
+        endif
+    endfor
+
+    return {}
+endfunction
+
+function! s:HandleInitializeResponse(conn, response) abort
+    let l:request_id = a:response.request_id
+    let l:project = s:FindProjectWithInitRequestID(a:conn, l:request_id)
+
+    if empty(l:project)
+        return
+    endif
+
+    " After the server starts, send messages we had queued previously.
+    for l:message_data in l:project.message_queue
+        call s:SendMessageData(a:conn, l:message_data)
+    endfor
+
+    " Remove the messages now.
+    let a:conn.message_queue = []
+endfunction
+
 function! ale#lsp#HandleMessage(conn, message) abort
     let a:conn.data .= a:message
 
@@ -149,8 +181,13 @@ function! ale#lsp#HandleMessage(conn, message) abort
 
     " Call our callbacks.
     for l:response in l:response_list
-        if has_key(a:conn, 'callback')
-            call ale#util#GetFunction(a:conn.callback)(l:response)
+        if get(l:response, 'method', '') ==# 'initialize'
+            call s:HandleInitializeResponse(a:conn, l:response)
+        else
+            " Call all of the registered handlers with the response.
+            for l:Callback in a:conn.callback_list
+                call ale#util#GetFunction(l:Callback)(l:response)
+            endfor
         endif
     endfor
 endfunction
@@ -169,11 +206,22 @@ function! s:HandleCommandMessage(job_id, message) abort
     call ale#lsp#HandleMessage(l:conn, a:message)
 endfunction
 
+function! s:RegisterProject(conn, project_root) abort
+    if !has_key(a:conn, a:project_root)
+        " Tools without project roots are ready right away, like tsserver.
+        let a:conn.projects[a:project_root] = {
+        \   'initialized': empty(a:project_root),
+        \   'init_messsage_id': 0,
+        \   'message_queue': [],
+        \}
+    endif
+endfunction
+
 " Start a program for LSP servers which run with executables.
 "
 " The job ID will be returned for for the program if it ran, otherwise
 " 0 will be returned.
-function! ale#lsp#StartProgram(executable, command, callback) abort
+function! ale#lsp#StartProgram(executable, command, project_root, callback) abort
     if !executable(a:executable)
         return 0
     endif
@@ -199,13 +247,15 @@ function! ale#lsp#StartProgram(executable, command, callback) abort
     endif
 
     let l:conn.id = l:job_id
-    let l:conn.callback = a:callback
+    " Add the callback to the List if it's not there already.
+    call uniq(sort(add(l:conn.callback_list, a:callback)))
+    call s:RegisterProject(l:conn, a:project_root)
 
     return l:job_id
 endfunction
 
 " Connect to an address and set up a callback for handling responses.
-function! ale#lsp#ConnectToAddress(address, callback) abort
+function! ale#lsp#ConnectToAddress(address, project_root, callback) abort
     let l:conn = s:FindConnection('id', a:address)
     " Get the current connection or a new one.
     let l:conn = !empty(l:conn) ? l:conn : s:NewConnection()
@@ -223,7 +273,22 @@ function! ale#lsp#ConnectToAddress(address, callback) abort
     endif
 
     let l:conn.id = a:address
-    let l:conn.callback = a:callback
+    " Add the callback to the List if it's not there already.
+    call uniq(sort(add(l:conn.callback_list, a:callback)))
+    call s:RegisterProject(l:conn, a:project_root)
+
+    return 1
+endfunction
+
+function! s:SendMessageData(conn, data) abort
+    if has_key(a:conn, 'executable')
+        call ale#job#SendRaw(a:conn.id, a:data)
+    elseif has_key(a:conn, 'channel') && ch_status(a:conn.channnel) ==# 'open'
+        " Send the message to the server
+        call ch_sendraw(a:conn.channel, a:data)
+    else
+        return 0
+    endif
 
     return 1
 endfunction
@@ -234,28 +299,60 @@ endfunction
 " Returns -1 when a message is sent, but no response is expected
 "          0 when the message is not sent and
 "          >= 1 with the message ID when a response is expected.
-function! ale#lsp#Send(conn_id, message) abort
+function! ale#lsp#Send(conn_id, message, ...) abort
+    let l:project_root = get(a:000, 0, '')
+
     let l:conn = s:FindConnection('id', a:conn_id)
+
+    if empty(l:conn)
+        return 0
+    endif
+
+    let l:project = get(l:conn.projects, l:project_root, {})
+
+    if empty(l:project)
+        return 0
+    endif
+
+    " If we haven't initialized the server yet, then send the message for it.
+    if !l:project.initialized
+        " Only send the init message once.
+        if !l:project.init_request_id
+            let [l:init_id, l:init_data] = ale#lsp#CreateMessageData(
+            \   ale#lsp#message#Initialize(l:conn.project_root),
+            \)
+
+            let l:project.init_request_id = l:init_id
+
+            call s:SendMessageData(l:conn, l:init_data)
+        endif
+    endif
+
     let [l:id, l:data] = ale#lsp#CreateMessageData(a:message)
 
-    if has_key(l:conn, 'executable')
-        call ale#job#SendRaw(l:conn.id, l:data)
-    elseif has_key(l:conn, 'channel') && ch_status(l:conn.channnel) ==# 'open'
-        " Send the message to the server
-        call ch_sendraw(l:conn.channel, l:data)
+    if l:project.initialized
+        " Send the message now.
+        call s:SendMessageData(l:conn, l:data)
     else
-        return 0
+        " Add the message we wanted to send to a List to send later.
+        call add(l:project.message_queue, l:data)
     endif
 
     return l:id == 0 ? -1 : l:id
 endfunction
 
-function! ale#lsp#OpenTSServerDocumentIfNeeded(conn_id, buffer) abort
+function! ale#lsp#OpenDocumentIfNeeded(conn_id, buffer, project_root, language_id) abort
     let l:conn = s:FindConnection('id', a:conn_id)
     let l:opened = 0
 
     if !empty(l:conn) && index(l:conn.open_documents, a:buffer) < 0
-        call ale#lsp#Send(a:conn_id, ale#lsp#tsserver_message#Open(a:buffer))
+        if empty(a:language_id)
+            let l:message = ale#lsp#tsserver_message#Open(a:buffer)
+        else
+            let l:message = ale#lsp#message#DidOpen(a:buffer, a:language_id)
+        endif
+
+        call ale#lsp#Send(a:conn_id, l:message, a:project_root)
         call add(l:conn.open_documents, a:buffer)
         let l:opened = 1
     endif
diff --git a/autoload/ale/lsp/message.vim b/autoload/ale/lsp/message.vim
index 937e4f46..7910247d 100644
--- a/autoload/ale/lsp/message.vim
+++ b/autoload/ale/lsp/message.vim
@@ -3,12 +3,32 @@
 "
 " Messages in this movie will be returned in the format
 " [is_notification, method_name, params?]
+let g:ale_lsp_next_version_id = 1
 
-function! ale#lsp#message#Initialize(root_uri) abort
+" The LSP protocols demands that we send every change to a document, including
+" undo, with incrementing version numbers, so we'll just use one incrementing
+" ID for everything.
+function! ale#lsp#message#GetNextVersionID() abort
+    " Use the current ID
+    let l:id = g:ale_lsp_next_version_id
+
+    " Increment the ID variable.
+    let g:ale_lsp_next_version_id += 1
+
+    " When the ID overflows, reset it to 1. By the time we hit the initial ID
+    " again, the messages will be long gone.
+    if g:ale_lsp_next_version_id < 1
+        let g:ale_lsp_next_version_id = 1
+    endif
+
+    return l:id
+endfunction
+
+function! ale#lsp#message#Initialize(root_path) abort
     " TODO: Define needed capabilities.
     return [0, 'initialize', {
     \   'processId': getpid(),
-    \   'rootUri': a:root_uri,
+    \   'rootPath': a:root_path,
     \   'capabilities': {},
     \}]
 endfunction
@@ -25,40 +45,44 @@ function! ale#lsp#message#Exit() abort
     return [1, 'exit']
 endfunction
 
-function! ale#lsp#message#DidOpen(uri, language_id, version, text) abort
+function! ale#lsp#message#DidOpen(buffer, language_id) abort
+    let l:lines = getbufline(a:buffer, 1, '$')
+
     return [1, 'textDocument/didOpen', {
     \   'textDocument': {
-    \       'uri': a:uri,
+    \       'uri': ale#path#ToURI(expand('#' . a:buffer . ':p')),
     \       'languageId': a:language_id,
-    \       'version': a:version,
-    \       'text': a:text,
+    \       'version': ale#lsp#message#GetNextVersionID(),
+    \       'text': join(l:lines, "\n"),
     \   },
     \}]
 endfunction
 
-function! ale#lsp#message#DidChange(uri, version, text) abort
+function! ale#lsp#message#DidChange(buffer) abort
+    let l:lines = getbufline(a:buffer, 1, '$')
+
     " For changes, we simply send the full text of the document to the server.
     return [1, 'textDocument/didChange', {
     \   'textDocument': {
-    \       'uri': a:uri,
-    \       'version': a:version,
+    \       'uri': ale#path#ToURI(expand('#' . a:buffer . ':p')),
+    \       'version': ale#lsp#message#GetNextVersionID(),
     \   },
-    \   'contentChanges': [{'text': a:text}]
+    \   'contentChanges': [{'text': join(l:lines, "\n")}]
     \}]
 endfunction
 
-function! ale#lsp#message#DidSave(uri) abort
+function! ale#lsp#message#DidSave(buffer) abort
     return [1, 'textDocument/didSave', {
     \   'textDocument': {
-    \       'uri': a:uri,
+    \       'uri': ale#path#ToURI(expand('#' . a:buffer . ':p')),
     \   },
     \}]
 endfunction
 
-function! ale#lsp#message#DidClose(uri) abort
+function! ale#lsp#message#DidClose(buffer) abort
     return [1, 'textDocument/didClose', {
     \   'textDocument': {
-    \       'uri': a:uri,
+    \       'uri': ale#path#ToURI(expand('#' . a:buffer . ':p')),
     \   },
     \}]
 endfunction
diff --git a/autoload/ale/lsp/response.vim b/autoload/ale/lsp/response.vim
index a2146f6a..13219ef6 100644
--- a/autoload/ale/lsp/response.vim
+++ b/autoload/ale/lsp/response.vim
@@ -8,11 +8,10 @@ let s:SEVERITY_INFORMATION = 3
 let s:SEVERITY_HINT = 4
 
 " Parse the message for textDocument/publishDiagnostics
-function! ale#lsp#response#ReadDiagnostics(params) abort
-    let l:filename = a:params.uri
+function! ale#lsp#response#ReadDiagnostics(response) abort
     let l:loclist = []
 
-    for l:diagnostic in a:params.diagnostics
+    for l:diagnostic in a:response.params.diagnostics
         let l:severity = get(l:diagnostic, 'severity', 0)
         let l:loclist_item = {
         \   'text': l:diagnostic.message,
@@ -40,7 +39,7 @@ function! ale#lsp#response#ReadDiagnostics(params) abort
         call add(l:loclist, l:loclist_item)
     endfor
 
-    return [l:filename, l:loclist]
+    return l:loclist
 endfunction
 
 function! ale#lsp#response#ReadTSServerDiagnostics(response) abort
diff --git a/autoload/ale/path.vim b/autoload/ale/path.vim
index 9ac3d8f2..c68114ae 100644
--- a/autoload/ale/path.vim
+++ b/autoload/ale/path.vim
@@ -141,3 +141,26 @@ function! ale#path#Upwards(path) abort
 
     return l:path_list
 endfunction
+
+" Convert a filesystem path to a file:// URI
+" relatives paths will not be prefixed with the protocol.
+" For Windows paths, the `:` in C:\ etc. will not be percent-encoded.
+function! ale#path#ToURI(path) abort
+    let l:has_drive_letter = a:path[1:2] ==# ':\'
+
+    return substitute(
+    \   ((l:has_drive_letter || a:path[:0] ==# '/') ? 'file://' : '')
+    \       . (l:has_drive_letter ? '/' . a:path[:2] : '')
+    \       . ale#uri#Encode(l:has_drive_letter ? a:path[3:] : a:path),
+    \   '\\',
+    \   '/',
+    \   'g',
+    \)
+endfunction
+
+function! ale#path#FromURI(uri) abort
+    let l:i = len('file://')
+    let l:encoded_path = a:uri[: l:i - 1] ==# 'file://' ? a:uri[l:i :] : a:uri
+
+    return ale#uri#Decode(l:encoded_path)
+endfunction
diff --git a/autoload/ale/uri.vim b/autoload/ale/uri.vim
new file mode 100644
index 00000000..934637d9
--- /dev/null
+++ b/autoload/ale/uri.vim
@@ -0,0 +1,18 @@
+" This probably doesn't handle Unicode characters well.
+function! ale#uri#Encode(value) abort
+    return substitute(
+    \   a:value,
+    \   '\([^a-zA-Z0-9\\/$\-_.!*''(),]\)',
+    \   '\=printf(''%%%02x'', char2nr(submatch(1)))',
+    \   'g'
+    \)
+endfunction
+
+function! ale#uri#Decode(value) abort
+    return substitute(
+    \   a:value,
+    \   '%\(\x\x\)',
+    \   '\=nr2char(''0x'' . submatch(1))',
+    \   'g'
+    \)
+endfunction
diff --git a/test/lsp/test_lsp_client_messages.vader b/test/lsp/test_lsp_client_messages.vader
index abf733ca..057abad4 100644
--- a/test/lsp/test_lsp_client_messages.vader
+++ b/test/lsp/test_lsp_client_messages.vader
@@ -1,10 +1,13 @@
 Before:
   silent! cd /testplugin/test/lsp
-  let b:dir = getcwd()
+  let g:dir = getcwd()
+  let g:ale_lsp_next_version_id = 1
+
+  call ale#test#SetFilename('foo/bar.ts')
 
 After:
-  silent execute 'cd ' . fnameescape(b:dir)
-  unlet! b:dir
+  silent execute 'cd ' . fnameescape(g:dir)
+  unlet! g:dir
 
 Execute(ale#lsp#message#Initialize() should return correct messages):
   AssertEqual
@@ -13,7 +16,7 @@ Execute(ale#lsp#message#Initialize() should return correct messages):
   \   'initialize',
   \   {
   \    'processId': getpid(),
-  \    'rootUri': '/foo/bar',
+  \    'rootPath': '/foo/bar',
   \    'capabilities': {},
   \   }
   \ ],
@@ -28,36 +31,51 @@ Execute(ale#lsp#message#Shutdown() should return correct messages):
 Execute(ale#lsp#message#Exit() should return correct messages):
   AssertEqual [1, 'exit'], ale#lsp#message#Exit(),
 
+Given typescript(A TypeScript file with 3 lines):
+  foo()
+  bar()
+  baz()
+
 Execute(ale#lsp#message#DidOpen() should return correct messages):
+  let g:ale_lsp_next_version_id = 12
   AssertEqual
   \ [
   \   1,
   \   'textDocument/didOpen',
   \   {
   \     'textDocument': {
-  \         'uri': '/foo/bar',
+  \         'uri': 'file://' . g:dir . '/foo/bar.ts',
   \         'languageId': 'typescript',
-  \         'version': 123,
-  \         'text': 'foobar',
+  \         'version': 12,
+  \         'text': "foo()\nbar()\nbaz()",
   \     },
   \   }
   \ ],
-  \ ale#lsp#message#DidOpen('/foo/bar', 'typescript', 123, 'foobar')
+  \ ale#lsp#message#DidOpen(bufnr(''), 'typescript')
 
 Execute(ale#lsp#message#DidChange() should return correct messages):
+  let g:ale_lsp_next_version_id = 34
+
   AssertEqual
   \ [
   \   1,
   \   'textDocument/didChange',
   \   {
   \     'textDocument': {
-  \         'uri': '/foo/bar',
-  \         'version': 123,
+  \         'uri': 'file://' . g:dir . '/foo/bar.ts',
+  \         'version': 34,
   \     },
-  \     'contentChanges': [{'text': 'foobar'}],
+  \     'contentChanges': [{'text': "foo()\nbar()\nbaz()"}],
   \   }
   \ ],
-  \ ale#lsp#message#DidChange('/foo/bar', 123, 'foobar')
+  \ ale#lsp#message#DidChange(bufnr(''))
+  " The version numbers should increment.
+  AssertEqual
+  \ 35,
+  \ ale#lsp#message#DidChange(bufnr(''))[2].textDocument.version
+  AssertEqual
+  \ 36,
+  \ ale#lsp#message#DidChange(bufnr(''))[2].textDocument.version
 
 Execute(ale#lsp#message#DidSave() should return correct messages):
   AssertEqual
@@ -66,11 +84,11 @@ Execute(ale#lsp#message#DidSave() should return correct messages):
   \   'textDocument/didSave',
   \   {
   \     'textDocument': {
-  \         'uri': '/foo/bar',
+  \         'uri': 'file://' . g:dir . '/foo/bar.ts',
   \     },
   \   }
   \ ],
-  \ ale#lsp#message#DidSave('/foo/bar')
+  \ ale#lsp#message#DidSave(bufnr(''))
 
 Execute(ale#lsp#message#DidClose() should return correct messages):
   AssertEqual
@@ -79,52 +97,41 @@ Execute(ale#lsp#message#DidClose() should return correct messages):
   \   'textDocument/didClose',
   \   {
   \     'textDocument': {
-  \         'uri': '/foo/bar',
+  \         'uri': 'file://' . g:dir . '/foo/bar.ts',
   \     },
   \   }
   \ ],
-  \ ale#lsp#message#DidClose('/foo/bar')
+  \ ale#lsp#message#DidClose(bufnr(''))
 
 Execute(ale#lsp#tsserver_message#Open() should return correct messages):
-  silent! noautocmd file foo.ts
-
   AssertEqual
   \ [
   \   1,
   \   'ts@open',
   \   {
-  \     'file': b:dir . '/foo.ts',
+  \     'file': g:dir . '/foo/bar.ts',
   \   }
   \ ],
   \ ale#lsp#tsserver_message#Open(bufnr(''))
 
 Execute(ale#lsp#tsserver_message#Close() should return correct messages):
-  silent! noautocmd file foo.ts
-
   AssertEqual
   \ [
   \   1,
   \   'ts@close',
   \   {
-  \     'file': b:dir . '/foo.ts',
+  \     'file': g:dir . '/foo/bar.ts',
   \   }
   \ ],
   \ ale#lsp#tsserver_message#Close(bufnr(''))
 
-Given typescript(A TypeScript file with 3 lines):
-  foo()
-  bar()
-  baz()
-
 Execute(ale#lsp#tsserver_message#Change() should return correct messages):
-  silent! noautocmd file foo.ts
-
   AssertEqual
   \ [
   \   1,
   \   'ts@change',
   \   {
-  \     'file': b:dir . '/foo.ts',
+  \     'file': g:dir . '/foo/bar.ts',
   \     'line': 1,
   \     'offset': 1,
   \     'endLine': 1073741824,
@@ -135,27 +142,23 @@ Execute(ale#lsp#tsserver_message#Change() should return correct messages):
   \ ale#lsp#tsserver_message#Change(bufnr(''))
 
 Execute(ale#lsp#tsserver_message#Geterr() should return correct messages):
-  silent! noautocmd file foo.ts
-
   AssertEqual
   \ [
   \   1,
   \   'ts@geterr',
   \   {
-  \     'files': [b:dir . '/foo.ts'],
+  \     'files': [g:dir . '/foo/bar.ts'],
   \   }
   \ ],
   \ ale#lsp#tsserver_message#Geterr(bufnr(''))
 
 Execute(ale#lsp#tsserver_message#Completions() should return correct messages):
-  silent! noautocmd file foo.ts
-
   AssertEqual
   \ [
   \   0,
   \   'ts@completions',
   \   {
-  \     'file': b:dir . '/foo.ts',
+  \     'file': g:dir . '/foo/bar.ts',
   \     'line': 347,
   \     'offset': 12,
   \     'prefix': 'abc',
@@ -164,14 +167,12 @@ Execute(ale#lsp#tsserver_message#Completions() should return correct messages):
   \ ale#lsp#tsserver_message#Completions(bufnr(''), 347, 12, 'abc')
 
 Execute(ale#lsp#tsserver_message#CompletionEntryDetails() should return correct messages):
-  silent! noautocmd file foo.ts
-
   AssertEqual
   \ [
   \   0,
   \   'ts@completionEntryDetails',
   \   {
-  \     'file': b:dir . '/foo.ts',
+  \     'file': g:dir . '/foo/bar.ts',
   \     'line': 347,
   \     'offset': 12,
   \     'entryNames': ['foo', 'bar'],
diff --git a/test/lsp/test_read_lsp_diagnostics.vader b/test/lsp/test_read_lsp_diagnostics.vader
index 63086a7f..3e637418 100644
--- a/test/lsp/test_read_lsp_diagnostics.vader
+++ b/test/lsp/test_read_lsp_diagnostics.vader
@@ -10,7 +10,7 @@ After:
   delfunction Range
 
 Execute(ale#lsp#response#ReadDiagnostics() should handle errors):
-  AssertEqual ['filename.ts', [
+  AssertEqual [
   \   {
   \     'type': 'E',
   \     'text': 'Something went wrong!',
@@ -20,18 +20,18 @@ Execute(ale#lsp#response#ReadDiagnostics() should handle errors):
   \     'end_col': 16,
   \     'nr': 'some-error',
   \   }
-  \ ]],
-  \ ale#lsp#response#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
+  \ ],
+  \ ale#lsp#response#ReadDiagnostics({'params': {'uri': 'filename.ts', 'diagnostics': [
   \   {
   \     'severity': 1,
   \     'range': Range(2, 10, 4, 15),
   \     'code': 'some-error',
   \     'message': 'Something went wrong!',
   \   },
-  \ ]})
+  \ ]}})
 
 Execute(ale#lsp#response#ReadDiagnostics() should handle warnings):
-  AssertEqual ['filename.ts', [
+  AssertEqual [
   \   {
   \     'type': 'W',
   \     'text': 'Something went wrong!',
@@ -41,18 +41,18 @@ Execute(ale#lsp#response#ReadDiagnostics() should handle warnings):
   \     'end_col': 4,
   \     'nr': 'some-warning',
   \   }
-  \ ]],
-  \ ale#lsp#response#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
+  \ ],
+  \ ale#lsp#response#ReadDiagnostics({'params': {'uri': 'filename.ts', 'diagnostics': [
   \   {
   \     'severity': 2,
   \     'range': Range(1, 3, 1, 3),
   \     'code': 'some-warning',
   \     'message': 'Something went wrong!',
   \   },
-  \ ]})
+  \ ]}})
 
 Execute(ale#lsp#response#ReadDiagnostics() should treat messages with missing severity as errors):
-  AssertEqual ['filename.ts', [
+  AssertEqual [
   \   {
   \     'type': 'E',
   \     'text': 'Something went wrong!',
@@ -62,17 +62,17 @@ Execute(ale#lsp#response#ReadDiagnostics() should treat messages with missing se
   \     'end_col': 16,
   \     'nr': 'some-error',
   \   }
-  \ ]],
-  \ ale#lsp#response#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
+  \ ],
+  \ ale#lsp#response#ReadDiagnostics({'params': {'uri': 'filename.ts', 'diagnostics': [
   \   {
   \     'range': Range(2, 10, 4, 15),
   \     'code': 'some-error',
   \     'message': 'Something went wrong!',
   \   },
-  \ ]})
+  \ ]}})
 
 Execute(ale#lsp#response#ReadDiagnostics() should handle messages without codes):
-  AssertEqual ['filename.ts', [
+  AssertEqual [
   \   {
   \     'type': 'E',
   \     'text': 'Something went wrong!',
@@ -81,16 +81,16 @@ Execute(ale#lsp#response#ReadDiagnostics() should handle messages without codes)
   \     'end_lnum': 5,
   \     'end_col': 16,
   \   }
-  \ ]],
-  \ ale#lsp#response#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
+  \ ],
+  \ ale#lsp#response#ReadDiagnostics({'params': {'uri': 'filename.ts', 'diagnostics': [
   \   {
   \     'range': Range(2, 10, 4, 15),
   \     'message': 'Something went wrong!',
   \   },
-  \ ]})
+  \ ]}})
 
 Execute(ale#lsp#response#ReadDiagnostics() should handle multiple messages):
-  AssertEqual ['filename.ts', [
+  AssertEqual [
   \   {
   \     'type': 'E',
   \     'text': 'Something went wrong!',
@@ -107,8 +107,8 @@ Execute(ale#lsp#response#ReadDiagnostics() should handle multiple messages):
   \     'end_lnum': 2,
   \     'end_col': 5,
   \   },
-  \ ]],
-  \ ale#lsp#response#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
+  \ ],
+  \ ale#lsp#response#ReadDiagnostics({'params': {'uri': 'filename.ts', 'diagnostics': [
   \   {
   \     'range': Range(0, 2, 0, 2),
   \     'message': 'Something went wrong!',
@@ -118,7 +118,7 @@ Execute(ale#lsp#response#ReadDiagnostics() should handle multiple messages):
   \     'range': Range(1, 4, 1, 4),
   \     'message': 'A warning',
   \   },
-  \ ]})
+  \ ]}})
 
 Execute(ale#lsp#response#ReadTSServerDiagnostics() should handle tsserver responses):
   AssertEqual [
diff --git a/test/test_linter_defintion_processing.vader b/test/test_linter_defintion_processing.vader
index 572591db..d946a600 100644
--- a/test/test_linter_defintion_processing.vader
+++ b/test/test_linter_defintion_processing.vader
@@ -372,6 +372,8 @@ Execute(PreProcess should accept tsserver LSP configuration):
   \ 'executable': 'x',
   \ 'command': 'x',
   \ 'lsp': 'tsserver',
+  \ 'language_callback': 'x',
+  \ 'project_root_callback': 'x',
   \}
 
   AssertEqual 'tsserver', ale#linter#PreProcess(g:linter).lsp
@@ -392,6 +394,8 @@ Execute(PreProcess should accept stdio LSP configuration):
   \ 'executable': 'x',
   \ 'command': 'x',
   \ 'lsp': 'stdio',
+  \ 'language_callback': 'x',
+  \ 'project_root_callback': 'x',
   \}
 
   AssertEqual 'stdio', ale#linter#PreProcess(g:linter).lsp
@@ -411,6 +415,8 @@ Execute(PreProcess should accept LSP server configurations):
   \ 'name': 'x',
   \ 'lsp': 'socket',
   \ 'address_callback': 'X',
+  \ 'language_callback': 'x',
+  \ 'project_root_callback': 'x',
   \}
 
   AssertEqual 'socket', ale#linter#PreProcess(g:linter).lsp
diff --git a/test/test_path_uri.vader b/test/test_path_uri.vader
new file mode 100644
index 00000000..dbceac3a
--- /dev/null
+++ b/test/test_path_uri.vader
@@ -0,0 +1,16 @@
+Execute(ale#path#ToURI should work for Windows paths):
+  AssertEqual 'file:///C:/foo/bar/baz.tst', ale#path#ToURI('C:\foo\bar\baz.tst')
+  AssertEqual 'foo/bar/baz.tst', ale#path#ToURI('foo\bar\baz.tst')
+
+Execute(ale#path#ToURI should work for Unix paths):
+  AssertEqual 'file:///foo/bar/baz.tst', ale#path#ToURI('/foo/bar/baz.tst')
+  AssertEqual 'foo/bar/baz.tst', ale#path#ToURI('foo/bar/baz.tst')
+
+Execute(ale#path#ToURI should keep safe characters):
+  AssertEqual '//a-zA-Z0-9$-_.!*''(),', ale#path#ToURI('\/a-zA-Z0-9$-_.!*''(),')
+
+Execute(ale#path#ToURI should percent encode unsafe characters):
+  AssertEqual '%20%2b%3a%3f%26%3d', ale#path#ToURI(' +:?&=')
+
+Execute(ale#path#FromURI should decode percent encodings):
+  AssertEqual ' +:?&=', ale#path#FromURI('%20%2b%3a%3f%26%3d')
diff --git a/test/util/test_cd_string_commands.vader b/test/util/test_cd_string_commands.vader
index b0b6c157..f8a97cb8 100644
--- a/test/util/test_cd_string_commands.vader
+++ b/test/util/test_cd_string_commands.vader
@@ -1,8 +1,15 @@
 Before:
   silent! cd /testplugin/test/util
+  let g:dir = getcwd()
+
+After:
+  silent execute 'cd ' . fnameescape(g:dir)
+  unlet! g:dir
 
 Execute(CdString should output the correct command string):
   AssertEqual 'cd ''/foo bar/baz'' && ', ale#path#CdString('/foo bar/baz')
 
 Execute(BufferCdString should output the correct command string):
-  AssertEqual 'cd ' . shellescape(getcwd()) . ' && ', ale#path#BufferCdString(bufnr(''))
+  call ale#test#SetFilename('foo.txt')
+
+  AssertEqual 'cd ' . shellescape(g:dir) . ' && ', ale#path#BufferCdString(bufnr(''))