From 6b862c6f23939ff16342e1b6faba2893c5030a05 Mon Sep 17 00:00:00 2001
From: Yuya Nishihara <yuya@tcha.org>
Date: Sun, 24 Dec 2023 11:49:36 +0900
Subject: [PATCH] cli: don't panic on empty alias substitution

This partially reverts 6c627fb30d76 "cli: default to log when no subcommand is
provided." We could reject an empty alias at all, but we would still need to
ensure that the expanded alias contained a subcommand name.

The help output is a bit odd as the <COMMAND> can be omitted, but I think
that's acceptable. If we do care about that, maybe we can override_usage().
---
 cli/src/cli_util.rs     |  6 +++++-
 cli/tests/test_alias.rs | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/cli/src/cli_util.rs b/cli/src/cli_util.rs
index de87c4dcc..ee2b87c0e 100644
--- a/cli/src/cli_util.rs
+++ b/cli/src/cli_util.rs
@@ -2777,7 +2777,11 @@ pub fn parse_args(
     layered_configs: &mut LayeredConfigs,
 ) -> Result<(ArgMatches, Args), CommandError> {
     handle_early_args(ui, app, string_args, layered_configs)?;
-    let matches = app.clone().try_get_matches_from(string_args)?;
+    let matches = app
+        .clone()
+        .arg_required_else_help(true)
+        .subcommand_required(true)
+        .try_get_matches_from(string_args)?;
 
     let args: Args = Args::from_arg_matches(&matches).unwrap();
     if args.global_args.verbose {
diff --git a/cli/tests/test_alias.rs b/cli/tests/test_alias.rs
index 146739c39..74b727327 100644
--- a/cli/tests/test_alias.rs
+++ b/cli/tests/test_alias.rs
@@ -71,12 +71,40 @@ fn test_alias_bad_name() {
     insta::assert_snapshot!(stderr, @r###"
     error: unrecognized subcommand 'foo.'
 
-    Usage: jj [OPTIONS] [COMMAND]
+    Usage: jj [OPTIONS] <COMMAND>
 
     For more information, try '--help'.
     "###);
 }
 
+#[test]
+fn test_alias_calls_empty_command() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    test_env.add_config(
+        r#"
+    aliases.empty = []
+    aliases.empty_command_with_opts = ["--no-pager"]
+    "#,
+    );
+    let stderr = test_env.jj_cmd_cli_error(&repo_path, &["empty"]);
+    insta::assert_snapshot!(stderr.lines().take(3).join("\n"), @r###"
+    Jujutsu (An experimental VCS)
+
+    Usage: jj [OPTIONS] <COMMAND>
+    "###);
+    let stderr = test_env.jj_cmd_cli_error(&repo_path, &["empty", "--no-pager"]);
+    insta::assert_snapshot!(stderr.lines().next().unwrap_or_default(), @r###"
+    error: 'jj' requires a subcommand but one was not provided
+    "###);
+    let stderr = test_env.jj_cmd_cli_error(&repo_path, &["empty_command_with_opts"]);
+    insta::assert_snapshot!(stderr.lines().next().unwrap_or_default(), @r###"
+    error: 'jj' requires a subcommand but one was not provided
+    "###);
+}
+
 #[test]
 fn test_alias_calls_unknown_command() {
     let test_env = TestEnvironment::default();
@@ -90,7 +118,7 @@ fn test_alias_calls_unknown_command() {
 
       tip: a similar subcommand exists: 'next'
 
-    Usage: jj [OPTIONS] [COMMAND]
+    Usage: jj [OPTIONS] <COMMAND>
 
     For more information, try '--help'.
     "###);
@@ -127,7 +155,7 @@ fn test_alias_calls_help() {
 
     To get started, see the tutorial at https://github.com/martinvonz/jj/blob/main/docs/tutorial.md.
 
-    Usage: jj [OPTIONS] [COMMAND]
+    Usage: jj [OPTIONS] <COMMAND>
     "###);
 }