Fix #1176 - Add an option for caching failing executable checks

autoload/ale/engine.vim

@@ -32,16 +32,20 @@ function! ale#engine#IsExecutable(buffer, executable) abort
         return 0
     endif
 
-    if has_key(s:executable_cache_map, a:executable)
-        return 1
+    " Check for a cached executable() check.
+    let l:result = get(s:executable_cache_map, a:executable, v:null)
+
+    if l:result isnot v:null
+        return l:result
     endif
 
-    let l:result = 0
+    " Check if the file is executable, and convert -1 to 1.
+    let l:result = executable(a:executable) isnot 0
 
-    if executable(a:executable)
-        let s:executable_cache_map[a:executable] = 1
-
-        let l:result = 1
+    " Cache the executable check if we found it, or if the option to cache
+    " failing checks is on.
+    if l:result || g:ale_cache_executable_check_failures
+        let s:executable_cache_map[a:executable] = l:result
     endif
 
     if g:ale_history_enabled

doc/ale.txt

@@ -605,6 +605,19 @@ g:airline#extensions#ale#enabled             *g:airline#extensions#ale#enabled*
   |airline#extensions#ale#warning_symbol|.
 
 
+g:ale_cache_executable_check_failures   *g:ale_cache_executable_check_failures*
+
+  Type: |Number|
+  Default: `0`
+
+  When set to `1`, ALE will cache failing executable checks for linters. By
+  default, only executable checks which succeed will be cached.
+
+  When this option is set to `1`, Vim will have to be restarted after new
+  executables are installed for ALE to be able to run linters for those
+  executables.
+
+
 g:ale_change_sign_column_color                 *g:ale_change_sign_column_color*
 
   Type: |Number|

plugin/ale.vim

@@ -188,6 +188,10 @@ let g:ale_history_enabled = get(g:, 'ale_history_enabled', 1)
 " A flag for storing the full output of commands in the history.
 let g:ale_history_log_output = get(g:, 'ale_history_log_output', 1)
 
+" A flag for caching failed executable checks.
+" This is off by default, because it will cause problems.
+call ale#Set('cache_executable_check_failures', 0)
+
 " A dictionary mapping regular expression patterns to arbitrary buffer
 " variables to be set. Useful for configuration ALE based on filename
 " patterns.

test/test_ale_info.vader

@@ -2,9 +2,13 @@ Before:
   Save g:ale_warn_about_trailing_whitespace
   Save g:ale_linters
   Save g:ale_fixers
+  Save g:ale_lint_on_text_changed
+  Save g:ale_cache_executable_check_failures
 
   unlet! b:ale_history
 
+  let g:ale_lint_on_text_changed = 'always'
+  let g:ale_cache_executable_check_failures = 0
   let g:ale_warn_about_trailing_whitespace = 1
 
   let g:testlinter1 = {'name': 'testlinter1', 'executable': 'testlinter1', 'command': 'testlinter1', 'callback': 'testCB1', 'output_stream': 'stdout'}
@@ -355,6 +359,31 @@ Execute (ALEInfo command history should print command output if logging is on):
 Execute (ALEInfo should include executable checks in the history):
   call ale#linter#Define('testft', g:testlinter1)
   call ale#engine#IsExecutable(bufnr(''), has('win32') ? 'cmd' : 'echo')
+  call ale#engine#IsExecutable(bufnr(''), has('win32') ? 'cmd' : 'echo')
+  call ale#engine#IsExecutable(bufnr(''), 'TheresNoWayThisIsExecutable')
+  call ale#engine#IsExecutable(bufnr(''), 'TheresNoWayThisIsExecutable')
+
+  call CheckInfo([
+  \   ' Current Filetype: testft.testft2',
+  \   'Available Linters: [''testlinter1'']',
+  \   '  Enabled Linters: [''testlinter1'']',
+  \ ' Linter Variables:',
+  \ '',
+  \] + g:globals_lines + g:command_header + [
+  \ '',
+  \ '(executable check - success) ' . (has('win32') ? 'cmd' : 'echo'),
+  \ '(executable check - failure) TheresNoWayThisIsExecutable',
+  \ '(executable check - failure) TheresNoWayThisIsExecutable',
+  \])
+
+Execute (The option for caching failing executable checks should work):
+  let g:ale_cache_executable_check_failures = 1
+
+  call ale#linter#Define('testft', g:testlinter1)
+
+  call ale#engine#IsExecutable(bufnr(''), has('win32') ? 'cmd' : 'echo')
+  call ale#engine#IsExecutable(bufnr(''), has('win32') ? 'cmd' : 'echo')
+  call ale#engine#IsExecutable(bufnr(''), 'TheresNoWayThisIsExecutable')
   call ale#engine#IsExecutable(bufnr(''), 'TheresNoWayThisIsExecutable')
 
   call CheckInfo([