patch 8.2.2955: Vim9: using filter in compiled command does not work

Problem:    Vim9: using filter in compiled command does not work.
Solution:   Generate EXEC including the command modifier.

src/ex_cmds.c

@@ -5277,6 +5277,16 @@ ex_drop(exarg_T *eap)
  */
     char_u *
 skip_vimgrep_pat(char_u *p, char_u **s, int *flags)
+{
+    return skip_vimgrep_pat_ext(p, s, flags, NULL, NULL);
+}
+
+/*
+ * As skip_vimgrep_pat() and store the character overwritten by NUL in "cp"
+ * and the pointer to it in "nulp".
+ */
+    char_u *
+skip_vimgrep_pat_ext(char_u *p, char_u **s, int *flags, char_u **nulp, int *cp)
 {
     int		c;
 
@@ -5287,8 +5297,15 @@ skip_vimgrep_pat(char_u *p, char_u **s, int *flags)
 	    *s = p;
 	p = skiptowhite(p);
 	if (s != NULL && *p != NUL)
+	{
+	    if (nulp != NULL)
+	    {
+		*nulp = p;
+		*cp = *p;
+	    }
 	    *p++ = NUL;
 	}
+    }
     else
     {
 	// ":vimgrep /pattern/[g][j] fname"
@@ -5301,7 +5318,14 @@ skip_vimgrep_pat(char_u *p, char_u **s, int *flags)
 
 	// Truncate the pattern.
 	if (s != NULL)
+	{
+	    if (nulp != NULL)
+	    {
+		*nulp = p;
+		*cp = *p;
+	    }
 	    *p = NUL;
+	}
 	++p;
 
 	// Find the flags

src/ex_docmd.c

@@ -2882,6 +2882,8 @@ parse_command_modifiers(
 	    case 'f':	// only accept ":filter {pat} cmd"
 			{
 			    char_u  *reg_pat;
+			    char_u  *nulp = NULL;
+			    int	    c = 0;
 
 			    if (!checkforcmd_noparen(&p, "filter", 4)
 						|| *p == NUL || ends_excmd(*p))
@@ -2902,7 +2904,8 @@ parse_command_modifiers(
 				p = skip_vimgrep_pat(p, NULL, NULL);
 			    else
 				// NOTE: This puts a NUL after the pattern.
-				p = skip_vimgrep_pat(p, &reg_pat, NULL);
+				p = skip_vimgrep_pat_ext(p, &reg_pat, NULL,
+								    &nulp, &c);
 			    if (p == NULL || *p == NUL)
 				break;
 			    if (!skip_only)
@@ -2911,6 +2914,9 @@ parse_command_modifiers(
 						vim_regcomp(reg_pat, RE_MAGIC);
 				if (cmod->cmod_filter_regmatch.regprog == NULL)
 				    break;
+				// restore the character overwritten by NUL
+				if (nulp != NULL)
+				    *nulp = c;
 			    }
 			    eap->cmd = p;
 			    continue;

src/proto/ex_cmds.pro

@@ -39,5 +39,6 @@ int prepare_tagpreview(int undo_sync, int use_previewpopup, use_popup_T use_popu
 void ex_smile(exarg_T *eap);
 void ex_drop(exarg_T *eap);
 char_u *skip_vimgrep_pat(char_u *p, char_u **s, int *flags);
+char_u *skip_vimgrep_pat_ext(char_u *p, char_u **s, int *flags, char_u **nulp, int *cp);
 void ex_oldfiles(exarg_T *eap);
 /* vim: set ft=c : */

src/testdir/test_vim9_cmd.vim

@@ -534,6 +534,14 @@ def Test_command_modifier_filter()
     assert_equal(execute('filter /piyo/ registers abc'), expected)
   END
   CheckDefAndScriptSuccess(lines)
+
+  # also do this compiled
+  lines =<< trim END
+      @a = 'very specific z3d37dh234 string'
+      filter z3d37dh234 registers
+      assert_match('very specific z3d37dh234 string', Screenline(&lines))
+  END
+  CheckDefAndScriptSuccess(lines)
 enddef
 
 def Test_win_command_modifiers()

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2955,
 /**/
     2954,
 /**/

src/vim9compile.c

@@ -8543,6 +8543,23 @@ compile_exec(char_u *line, exarg_T *eap, cctx_T *cctx)
     if (cctx->ctx_skip == SKIP_YES)
 	goto theend;
 
+    // If there was a prececing command modifier, drop it and include it in the
+    // EXEC command.
+    if (cctx->ctx_has_cmdmod)
+    {
+	garray_T	*instr = &cctx->ctx_instr;
+	isn_T		*isn = ((isn_T *)instr->ga_data) + instr->ga_len - 1;
+
+	if (isn->isn_type == ISN_CMDMOD)
+	{
+	    vim_regfree(isn->isn_arg.cmdmod.cf_cmdmod
+					       ->cmod_filter_regmatch.regprog);
+	    vim_free(isn->isn_arg.cmdmod.cf_cmdmod);
+	    --instr->ga_len;
+	    cctx->ctx_has_cmdmod = FALSE;
+	}
+    }
+
     if (eap->cmdidx >= 0 && eap->cmdidx < CMD_SIZE)
     {
 	long	argt = eap->argt;