From 2f9c2df10ddd06a6e51d7016ce688ff6f6fde12d Mon Sep 17 00:00:00 2001
From: Nahor <nahor.j+github@gmail.com>
Date: Tue, 31 Mar 2026 18:17:43 -0700
Subject: [PATCH] set: report an error when called with `-a`,`-p` and no `NAME`

Previously executing `set -a` or `set -p` would just list all the
variables, which does not make sense since the user specifically ask
for an action (append/prepend).

Update the help page synopsis

Part of #12603
---
 doc_src/cmds/set.rst  | 17 +++++++++--------
 src/builtins/set.rs   |  4 ++--
 tests/checks/set.fish | 26 ++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/doc_src/cmds/set.rst b/doc_src/cmds/set.rst
index b5ca41c4a..d73f47102 100644
--- a/doc_src/cmds/set.rst
+++ b/doc_src/cmds/set.rst
@@ -6,16 +6,17 @@ Synopsis
 
 .. synopsis::
 
-    set
-    set (-f | --function) (-l | --local) (-g | --global) (-U | --universal) [--no-event]
-    set [-Uflg] NAME [VALUE ...]
-    set [-Uflg] NAME[[INDEX ...]] [VALUE ...]
-    set (-x | --export) (-u | --unexport) [-Uflg] NAME [VALUE ...]
-    set (-a | --append) (-p | --prepend) [-Uflg] NAME VALUE ...
-    set (-e | --erase) [-Uflg] [-xu] [NAME][[INDEX]] ...]
-    set (-q | --query) [-Uflg] [-xu] [NAME][[INDEX]] ...]
+    set [(-f | --function) (-l | --local) (-g | --global) (-U | --universal)]
+        [(-x | --export) (-u | --unexport)]
     set (-S | --show) (-L | --long) [NAME ...]
 
+    set [-Uflg] [-xu] [--no-event] NAME [VALUE ...]
+    set [-Uflg] [--no-event] NAME[[INDEX ...]] [VALUE ...]
+    set (-a | --append) (-p | --prepend) [-Uflg] [--no-event] NAME VALUE ...
+    set (-e | --erase) [-Uflg] [--no-event] NAME[[INDEX]] ...
+
+    set (-q | --query) [-Uflg] [-xu] NAME[[INDEX]] ...
+
 Description
 -----------
 
diff --git a/src/builtins/set.rs b/src/builtins/set.rs
index 5a8910395..f0183defa 100644
--- a/src/builtins/set.rs
+++ b/src/builtins/set.rs
@@ -945,7 +945,7 @@ fn set_internal(
     if argv.is_empty() {
         streams
             .err
-            .appendln(&wgettext_fmt!(BUILTIN_ERR_MIN_ARG_COUNT1, cmd, 1));
+            .appendln(&wgettext_fmt!(BUILTIN_ERR_MIN_ARG_COUNT1, cmd, 1, 0));
         builtin_print_error_trailer(parser, streams.err, cmd);
         return Err(STATUS_INVALID_ARGS);
     }
@@ -1045,7 +1045,7 @@ pub fn set(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> Buil
         list(&opts, parser, streams)
     } else if opts.show {
         show(cmd, parser, streams, args)
-    } else if args.is_empty() {
+    } else if args.is_empty() && !(opts.append || opts.prepend) {
         list(&opts, parser, streams)
     } else {
         set_internal(cmd, &opts, parser, streams, args)
diff --git a/tests/checks/set.fish b/tests/checks/set.fish
index cda623520..25fe71a99 100644
--- a/tests/checks/set.fish
+++ b/tests/checks/set.fish
@@ -625,6 +625,19 @@ set --show var5
 #CHECK: $var5[7]: |x|
 #CHECK: $var5[8]: |0|
 
+set -a
+# CHECKERR: set: expected >= 1 arguments; got 0
+# CHECKERR: {{.*}}checks/set.fish (line {{\d+}}):
+# CHECKERR: set -a
+# CHECKERR: ^
+# CHECKERR: (Type 'help set' for related documentation)
+set -p
+# CHECKERR: set: expected >= 1 arguments; got 0
+# CHECKERR: {{.*}}checks/set.fish (line {{\d+}}):
+# CHECKERR: set -p
+# CHECKERR: ^
+# CHECKERR: (Type 'help set' for related documentation)
+
 # Setting local scope when no local scope of the var uses the closest scope
 set -g var6 ghi jkl
 begin
@@ -676,6 +689,19 @@ env | grep TESTVAR | sort | cat -v
 #CHECK: TESTVAR1=a
 #CHECK: TESTVAR2=a b
 
+set -x | grep TESTVAR | sort | cat -v
+#CHECK: TESTVAR0
+#CHECK: TESTVAR1 a
+#CHECK: TESTVAR2 'a' 'b'
+
+set -u TESTVAR0
+set -u TESTVAR2 a b
+set -u | grep TESTVAR | sort | cat -v
+#CHECK: TESTVAR0
+#CHECK: TESTVAR2 'a' 'b'
+set -x | grep TESTVAR | sort | cat -v
+#CHECK: TESTVAR1 a
+
 # if/for/while scope
 function test_ifforwhile_scope
     if set -l ifvar1 (true && echo val1)