From efd83d441ba14eaadf5df4c7c29fddebb2a24780 Mon Sep 17 00:00:00 2001
From: Hirohito Higashi <h.east.727@gmail.com>
Date: Fri, 8 Aug 2025 13:25:27 +0200
Subject: [PATCH] patch 9.1.1607: :apple command detected as :append

Problem:  :apple command detected as :append (dai475694450)
Solution: Disallow to define a custom command with lower-case letter,
          correctly detect :insert/:change/:append ex commands
          (Hirohito Higashi).

fixes: #17893
closes: #17930

Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/testdir/test_vimscript.vim | 46 ++++++++++++++++++++++++++++++++++
 src/userfunc.c                 | 20 ++++++---------
 src/version.c                  |  2 ++
 3 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index af78d1c93d..e1b0425ee7 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -6888,6 +6888,52 @@ func Test_script_lines()
     catch
 	call assert_exception('Vim(function):E1145: Missing heredoc end marker: .')
     endtry
+
+    " More test for :append, :change, :insert
+    let cmds = ["append", "change", "insert"]
+    let suffixes = ["", "!", "|", "|xyz", " "]
+
+    for c in cmds
+      " Single character (with some accepted trailing characters)
+      for s in suffixes
+        let cmd = c[:0] .. s
+        let line = ["func LinesCheck()", cmd, "", "endfunc", "call LinesCheck()"]
+        call writefile(line, 'Xfunc', 'D')
+        call assert_fails('source Xfunc', 'E1145: Missing heredoc end marker: .', $'"{cmd}"')
+      endfor
+
+      " Unnecessary arguments
+      let cmd = c[:2] .. " end"
+      let line[1] = cmd
+      call writefile(line, 'Xfunc', 'D')
+      call assert_fails('source Xfunc', 'E488: Trailing characters: end:', $'"{cmd}"')
+
+      " Extra characters at the end (i.e., other commands)
+      let cmd = c .. "x"
+      let line[1] = cmd
+      call writefile(line, 'Xfunc', 'D')
+      call assert_fails('source Xfunc', 'E492: Not an editor command:', $'"{cmd}"')
+    endfor
+
+    let line =<< trim END
+    func AppendCheck()
+      apple
+    endfunc
+    call AppendCheck()
+    END
+    call writefile(line, 'Xfunc', 'D')
+    call assert_fails('source Xfunc', 'E492: Not an editor command:   apple')
+
+    let line =<< trim END
+    func AppendCheck()
+      command! apple :echo "hello apple"
+      apple
+    endfunc
+    call AppendCheck()
+    END
+    call writefile(line, 'Xfunc', 'D')
+    call assert_fails('source Xfunc', 'E183: User defined commands must start with an uppercase letter')
+
 endfunc
 
 "-------------------------------------------------------------------------------
diff --git a/src/userfunc.c b/src/userfunc.c
index dbd6a4ef15..a4d01524ab 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -1282,21 +1282,15 @@ get_function_body(
 	    }
 
 	    // Check for ":append", ":change", ":insert".  Not for :def.
-	    p = skip_range(p, FALSE, NULL);
+	    char_u *tp = p = skip_range(p, FALSE, NULL);
 	    if (!vim9_function
-		&& ((p[0] == 'a' && (!ASCII_ISALPHA(p[1]) || p[1] == 'p'))
-		    || (p[0] == 'c'
-			&& (!ASCII_ISALPHA(p[1]) || (p[1] == 'h'
-				&& (!ASCII_ISALPHA(p[2]) || (p[2] == 'a'
-					&& (STRNCMP(&p[3], "nge", 3) != 0
-					    || !ASCII_ISALPHA(p[6])))))))
-		    || (p[0] == 'i'
-			&& (!ASCII_ISALPHA(p[1]) || (p[1] == 'n'
-				&& (!ASCII_ISALPHA(p[2])
-				    || (p[2] == 's'
-					&& (!ASCII_ISALPHA(p[3])
-						|| p[3] == 'e'))))))))
+		&& (checkforcmd(&p, "append", 1)
+		    || checkforcmd(&p, "change", 1)
+		    || checkforcmd(&p, "insert", 1))
+		    && (*p == '!' || *p == '|' || IS_WHITE_NL_OR_NUL(*p)))
 		skip_until = vim_strnsave((char_u *)".", 1);
+	    else
+		p = tp;
 
 	    // Check for ":python <<EOF", ":tcl <<EOF", etc.
 	    arg = skipwhite(skiptowhite(p));
diff --git a/src/version.c b/src/version.c
index d07747c958..9ba90af671 100644
--- a/src/version.c
+++ b/src/version.c
@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1607,
 /**/
     1606,
 /**/