vim-patch:9.0.0379: cleaning up after writefile() is a hassle

Problem:    Cleaning up after writefile() is a hassle.
Solution:   Add the 'D' flag to defer deleting the written file.  Very useful
            in tests.

806a273f3c

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/eval/funcs.c

@@ -9296,6 +9296,7 @@ static void f_writefile(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   bool binary = false;
   bool append = false;
+  bool defer = false;
   bool do_fsync = !!p_fs;
   bool mkdir_p = false;
   if (argvars[2].v_type != VAR_UNKNOWN) {
@@ -9309,6 +9310,8 @@ static void f_writefile(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
         binary = true; break;
       case 'a':
         append = true; break;
+      case 'D':
+        defer = true; break;
       case 's':
         do_fsync = true; break;
       case 'S':
@@ -9328,6 +9331,12 @@ static void f_writefile(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   if (fname == NULL) {
     return;
   }
+
+  if (defer && get_current_funccal() == NULL) {
+    semsg(_(e_str_not_inside_function), "defer");
+    return;
+  }
+
   FileDescriptor fp;
   int error;
   if (*fname == NUL) {
@@ -9336,9 +9345,17 @@ static void f_writefile(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
                                 ((append ? kFileAppend : kFileTruncate)
                                  | (mkdir_p ? kFileMkDir : kFileCreate)
                                  | kFileCreate), 0666)) != 0) {
-    semsg(_("E482: Can't open file %s for writing: %s"),
-          fname, os_strerror(error));
+    semsg(_("E482: Can't open file %s for writing: %s"), fname, os_strerror(error));
   } else {
+    if (defer) {
+      typval_T tv = {
+        .v_type = VAR_STRING,
+        .v_lock = VAR_UNLOCKED,
+        .vval.v_string = xstrdup(fname),
+      };
+      add_defer("delete", 1, &tv);
+    }
+
     bool write_ok;
     if (argvars[0].v_type == VAR_BLOB) {
       write_ok = write_blob(&fp, argvars[0].vval.v_blob);

src/nvim/eval/userfunc.c

@@ -478,6 +478,7 @@ void emsg_funcname(const char *errmsg, const char *name)
 
 /// Get function arguments at "*arg" and advance it.
 /// Return them in "*argvars[MAX_FUNC_ARGS + 1]" and the count in "argcount".
+/// On failure FAIL is returned but the "argvars[argcount]" are still set.
 static int get_func_arguments(char **arg, evalarg_T *const evalarg, int partial_argc,
                               typval_T *argvars, int *argcount)
 {
@@ -3119,16 +3120,28 @@ static int ex_defer_inner(char *name, char **arg, evalarg_T *const evalarg)
 {
   typval_T argvars[MAX_FUNC_ARGS + 1];  // vars for arguments
   int argcount = 0;  // number of arguments found
-  int ret = FAIL;
 
   if (current_funccal == NULL) {
     semsg(_(e_str_not_inside_function), "defer");
     return FAIL;
   }
   if (get_func_arguments(arg, evalarg, false, argvars, &argcount) == FAIL) {
-    goto theend;
+    while (--argcount >= 0) {
+      tv_clear(&argvars[argcount]);
+    }
+    return FAIL;
   }
+  add_defer(name, argcount, argvars);
+  return OK;
+}
+
+/// Add a deferred call for "name" with arguments "argvars[argcount]".
+/// Consumes "argvars[]".
+/// Caller must check that current_funccal is not NULL.
+void add_defer(char *name, int argcount_arg, typval_T *argvars)
+{
   char *saved_name = xstrdup(name);
+  int argcount = argcount_arg;
 
   if (current_funccal->fc_defer.ga_itemsize == 0) {
     ga_init(&current_funccal->fc_defer, sizeof(defer_T), 10);
@@ -3140,13 +3153,6 @@ static int ex_defer_inner(char *name, char **arg, evalarg_T *const evalarg)
     argcount--;
     dr->dr_argvars[argcount] = argvars[argcount];
   }
-  ret = OK;
-
-theend:
-  while (--argcount >= 0) {
-    tv_clear(&argvars[argcount]);
-  }
-  return ret;
 }
 
 /// Invoked after a function has finished: invoke ":defer" functions.