Fix #3247 - Use --always-make for make -n by default

autoload/ale/c.vim

@@ -2,7 +2,9 @@
 " Description: Functions for integrating with C-family linters.
 
 call ale#Set('c_parse_makefile', 0)
+call ale#Set('c_always_make', has('unix') && !has('macunix'))
 call ale#Set('c_parse_compile_commands', 1)
+
 let s:sep = has('win32') ? '\' : '/'
 
 " Set just so tests can override it.
@@ -504,7 +506,10 @@ function! ale#c#GetMakeCommand(buffer) abort
         let l:path = ale#path#FindNearestFile(a:buffer, 'Makefile')
 
         if !empty(l:path)
-            return ale#path#CdString(fnamemodify(l:path, ':h')) . 'make -n'
+            let l:always_make = ale#Var(a:buffer, 'c_always_make')
+
+            return ale#path#CdString(fnamemodify(l:path, ':h'))
+            \   . 'make -n' . (l:always_make ? ' --always-make' : '')
         endif
     endif
 

doc/ale-c.txt

@@ -8,6 +8,17 @@ runs either `clang`, or `gcc`. See |ale-c-cc|.
 ===============================================================================
 Global Options
 
+g:ale_c_always_make                                       *g:ale_c_always_make*
+                                                          *b:ale_c_always_make*
+  Type: |Number|
+  Default: `has('unix') && !has('macunix')`
+
+  If set to `1`, use `--always-make` for `make`, which means that output will
+  always be parsed from `make` dry runs with GNU make. BSD `make` does not
+  support this option, so you probably want to turn this option off when using
+  a BSD variant.
+
+
 g:ale_c_build_dir_names                               *g:ale_c_build_dir_names*
                                                       *b:ale_c_build_dir_names*
 
@@ -58,6 +69,11 @@ g:ale_c_parse_makefile                                 *g:ale_c_parse_makefile*
   set for C or C++ compilers. This can make it easier to determine the correct
   build flags to use for different files.
 
+  NOTE: When using this option on BSD, you may need to set
+  |g:ale_c_always_make| to `0`, and `make -n` will not provide consistent
+  results if binaries have already been built, so use `make clean` when
+  editing your files.
+
   WARNING: Running `make -n` automatically can execute arbitrary code, even
   though it's supposed to be a dry run, so enable this option with care. You
   might prefer to use the buffer-local version of the option instead with

doc/ale-cpp.txt

@@ -10,6 +10,7 @@ Global Options
 
 The following C options also apply to some C++ linters too.
 
+* |g:ale_c_always_make|
 * |g:ale_c_build_dir_names|
 * |g:ale_c_build_dir|
 * |g:ale_c_parse_makefile|

test/test_c_flag_parsing.vader

@@ -1,9 +1,13 @@
 Before:
   Save g:ale_c_parse_makefile
+  Save g:ale_c_always_make
+  Save b:ale_c_always_make
 
   call ale#test#SetDirectory('/testplugin/test')
 
   let g:ale_c_parse_makefile = 1
+  let g:ale_c_always_make = 1
+  let b:ale_c_always_make = 1
 
   function SplitAndParse(path_prefix, command) abort
     let l:args = ale#c#ShellSplit(a:command)
@@ -18,6 +22,22 @@ After:
 
   call ale#test#RestoreDirectory()
 
+Execute(The make command should be correct):
+  call ale#test#SetFilename('test_c_projects/makefile_project/subdir/file.c')
+
+  AssertEqual
+  \ ale#path#CdString(ale#path#Simplify(g:dir. '/test_c_projects/makefile_project'))
+  \   . 'make -n --always-make',
+  \ ale#c#GetMakeCommand(bufnr(''))
+
+  " You should be able to disable --always-make for a buffer.
+  let b:ale_c_always_make = 0
+
+  AssertEqual
+  \ ale#path#CdString(ale#path#Simplify(g:dir. '/test_c_projects/makefile_project'))
+  \   . 'make -n',
+  \ ale#c#GetMakeCommand(bufnr(''))
+
 Execute(The CFlags parser should be able to parse include directives):
   call ale#test#SetFilename('test_c_projects/makefile_project/subdir/file.c')