Close #2281 - Separate cwd commands from commands

Working directories are now set seperately from the commands so they
can later be swapped out when running linters over projects is
supported, and also better support filename mapping for running linters
on other machines in future.

autoload/ale/command.vim

@@ -7,6 +7,9 @@ if !exists('s:buffer_data')
     let s:buffer_data = {}
 endif
 
+" The regular expression used for formatting filenames with modifiers.
+let s:path_format_regex = '\v\%s(%(:h|:t|:r|:e)*)'
+
 " Used to get the data in tests.
 function! ale#command#GetData() abort
     return deepcopy(s:buffer_data)
@@ -26,6 +29,19 @@ function! ale#command#InitData(buffer) abort
     endif
 endfunction
 
+" Set the cwd for commands that are about to run.
+" Used internally.
+function! ale#command#SetCwd(buffer, cwd) abort
+    call ale#command#InitData(a:buffer)
+    let s:buffer_data[a:buffer].cwd = a:cwd
+endfunction
+
+function! ale#command#ResetCwd(buffer) abort
+    if has_key(s:buffer_data, a:buffer)
+        let s:buffer_data[a:buffer].cwd = v:null
+    endif
+endfunction
+
 function! ale#command#ManageFile(buffer, file) abort
     call ale#command#InitData(a:buffer)
     call add(s:buffer_data[a:buffer].file_list, a:file)
@@ -151,6 +167,24 @@ function! s:FormatFilename(filename, mappings, modifiers) abort
     return ale#Escape(l:filename)
 endfunction
 
+" Produce a command prefix to check to a particular directory for a command.
+" %s format markers with filename-modifiers can be used as the directory, and
+" will be returned verbatim for formatting in paths relative to files.
+function! ale#command#CdString(directory) abort
+    let l:match = matchstrpos(a:directory, s:path_format_regex)
+    " Do not escape the directory here if it's a valid format string.
+    " This allows us to use sequences like %s:h, %s:h:h, etc.
+    let l:directory = l:match[1:] == [0, len(a:directory)]
+    \   ? a:directory
+    \   : ale#Escape(a:directory)
+
+    if has('win32')
+        return 'cd /d ' . l:directory . ' && '
+    endif
+
+    return 'cd ' . l:directory . ' && '
+endfunction
+
 " Given a command string, replace every...
 " %s -> with the current filename
 " %t -> with the name of an unused file in a temporary directory
@@ -161,11 +195,16 @@ function! ale#command#FormatCommand(
 \   command,
 \   pipe_file_if_needed,
 \   input,
+\   cwd,
 \   mappings,
 \) abort
     let l:temporary_file = ''
     let l:command = a:command
 
+    if !empty(a:cwd)
+        let l:command = ale#command#CdString(a:cwd) . l:command
+    endif
+
     " First replace all uses of %%, used for literal percent characters,
     " with an ugly string.
     let l:command = substitute(l:command, '%%', '<<PERCENTS>>', 'g')
@@ -181,7 +220,7 @@ function! ale#command#FormatCommand(
         let l:filename = fnamemodify(bufname(a:buffer), ':p')
         let l:command = substitute(
         \   l:command,
-        \   '\v\%s(%(:h|:t|:r|:e)*)',
+        \   s:path_format_regex,
         \   '\=s:FormatFilename(l:filename, a:mappings, submatch(1))',
         \   'g'
         \)
@@ -279,9 +318,16 @@ function! s:ExitCallback(buffer, line_list, Callback, data) abort
     let l:result = a:data.result
     let l:result.value = l:value
 
-    if get(l:result, 'result_callback', v:null) isnot v:null
-        call call(l:result.result_callback, [l:value])
-    endif
+    " Set the default cwd for this buffer in this call stack.
+    call ale#command#SetCwd(a:buffer, l:result.cwd)
+
+    try
+        if get(l:result, 'result_callback', v:null) isnot v:null
+            call call(l:result.result_callback, [l:value])
+        endif
+    finally
+        call ale#command#ResetCwd(a:buffer)
+    endtry
 endfunction
 
 function! ale#command#Run(buffer, command, Callback, ...) abort
@@ -293,6 +339,13 @@ function! ale#command#Run(buffer, command, Callback, ...) abort
 
     let l:output_stream = get(l:options, 'output_stream', 'stdout')
     let l:line_list = []
+    let l:cwd = get(l:options, 'cwd', v:null)
+
+    if l:cwd is v:null
+        " Default the working directory to whatever it was for the last
+        " command run in the chain.
+        let l:cwd = get(get(s:buffer_data, a:buffer, {}), 'cwd', v:null)
+    endif
 
     let [l:temporary_file, l:command, l:file_created] = ale#command#FormatCommand(
     \   a:buffer,
@@ -300,6 +353,7 @@ function! ale#command#Run(buffer, command, Callback, ...) abort
     \   a:command,
     \   get(l:options, 'read_buffer', 0),
     \   get(l:options, 'input', v:null),
+    \   l:cwd,
     \   get(l:options, 'filename_mappings', []),
     \)
     let l:command = ale#job#PrepareCommand(a:buffer, l:command)
@@ -366,10 +420,14 @@ function! ale#command#Run(buffer, command, Callback, ...) abort
     " The `_deferred_job_id` is used for both checking the type of object, and
     " for checking the job ID and status.
     "
+    " The cwd is kept and used as the default value for the next command in
+    " the chain.
+    "
     " The original command here is used in tests.
     let l:result = {
     \   '_deferred_job_id': l:job_id,
     \   'executable': get(l:options, 'executable', ''),
+    \   'cwd': l:cwd,
     \   'command': a:command,
     \}