move check_file_readonly() into /src/os/fs.c and rename it

src/ex_cmds.c

@@ -2496,15 +2496,11 @@ int not_writing(void)
  */
 static int check_readonly(int *forceit, buf_T *buf)
 {
-  struct stat st;
-
   /* Handle a file being readonly when the 'readonly' option is set or when
-   * the file exists and permissions are read-only.
+   * the file exists and permissions are read-only. */
-   * We will send 0777 to check_file_readonly(), as the "perm" variable is
-   * important for device checks but not here. */
   if (!*forceit && (buf->b_p_ro
-                    || (mch_stat((char *)buf->b_ffname, &st) >= 0
+                    || (os_file_exists(buf->b_ffname)
-                        && check_file_readonly(buf->b_ffname, 0777)))) {
+                        && os_file_is_readonly((char *)buf->b_ffname)))) {
     if ((p_confirm || cmdmod.confirm) && buf->b_fname != NULL) {
       char_u buff[DIALOG_MSG_SIZE];
 

src/fileio.c

@@ -71,9 +71,6 @@ static int crypt_seed_len[] = {0, 8};
 #define CRYPT_SALT_LEN_MAX 8
 #define CRYPT_SEED_LEN_MAX 8
 
-/* Is there any system that doesn't have access()? */
-#define USE_MCH_ACCESS
-
 static char_u *next_fenc(char_u **pp);
 static char_u *readfile_charconvert(char_u *fname, char_u *fenc,
                                             int *fdp);
@@ -2443,34 +2440,6 @@ set_file_time (
 }
 #endif /* UNIX */
 
-
-/*
- * Return TRUE if a file appears to be read-only from the file permissions.
- */
-int 
-check_file_readonly (
-    char_u *fname,             /* full path to file */
-    int perm                       /* known permissions on file */
-)
-{
-#ifndef USE_MCH_ACCESS
-  int fd = 0;
-#endif
-
-  return
-#ifdef USE_MCH_ACCESS
-# ifdef UNIX
-    (perm & 0222) == 0 ||
-# endif
-    mch_access((char *)fname, W_OK)
-#else
-    (fd = mch_open((char *)fname, O_RDWR | O_EXTRA, 0)) < 0
-    ? TRUE : (close(fd), FALSE)
-#endif
-  ;
-}
-
-
 /*
  * buf_write() - write to file "fname" lines "start" through "end"
  *
@@ -2887,7 +2856,7 @@ buf_write (
      * Check if the file is really writable (when renaming the file to
      * make a backup we won't discover it later).
      */
-    file_readonly = check_file_readonly(fname, (int)perm);
+    file_readonly = os_file_is_readonly((char *)fname);
 
     if (!forceit && file_readonly) {
       if (vim_strchr(p_cpo, CPO_FWRITE) != NULL) {

src/os/fs.c

@@ -278,3 +278,13 @@ int os_file_exists(const char_u *name)
   }
 }
 
+// return TRUE if a file appears to be read-only from the file permissions.
+int os_file_is_readonly(const char *name)
+{
+  if (mch_access(name, W_OK) == 0) {
+    return FALSE;
+  } else {
+    return TRUE;
+  }
+}
+

src/os/os.h

@@ -68,5 +68,6 @@ int os_get_usernames(garray_T *usernames);
 int os_get_user_name(char *s, size_t len);
 int os_get_uname(uid_t uid, char *s, size_t len);
 char *os_get_user_directory(const char *name);
+int os_file_is_readonly(const char *name);
 
 #endif  // NEOVIM_OS_OS_H

test/unit/os/fs.moon

@@ -19,6 +19,7 @@ int os_can_exe(char_u *name);
 int32_t os_getperm(char_u *name);
 int os_setperm(char_u *name, long perm);
 int os_file_exists(const char_u *name);
+int os_file_is_readonly(char *fname);
 ]]
 
 -- import constants parsed by ffi
@@ -282,6 +283,9 @@ describe 'fs function', ->
     os_setperm = (filename, perm) ->
       fs.os_setperm (to_cstr filename), perm
 
+    os_file_is_readonly = (filename) ->
+      fs.os_file_is_readonly (to_cstr filename)
+
     bit_set = (number, check_bit) ->
       if 0 == (bit.band number, check_bit) then false else true
 
@@ -322,6 +326,20 @@ describe 'fs function', ->
         perm = ffi.C.kS_IXUSR
         eq FAIL, (os_setperm 'non-existing-file', perm)
 
+    describe 'os_file_is_readonly', ->
+      it 'returns TRUE if the file is readonly', ->
+        perm = os_getperm 'unit-test-directory/test.file'
+        perm_orig = perm
+        perm = unset_bit perm, ffi.C.kS_IWUSR
+        perm = unset_bit perm, ffi.C.kS_IWGRP
+        perm = unset_bit perm, ffi.C.kS_IWOTH
+        eq OK, (os_setperm 'unit-test-directory/test.file', perm)
+        eq TRUE, os_file_is_readonly 'unit-test-directory/test.file'
+        eq OK, (os_setperm 'unit-test-directory/test.file', perm_orig)
+
+      it 'returns FALSE if the file is writable', ->
+        eq FALSE, os_file_is_readonly 'unit-test-directory/test.file'
+
   describe 'os_file_exists', ->
     os_file_exists = (filename) ->
       fs.os_file_exists (to_cstr filename)