From 45851ef31e3542df3fe924b2417a209ef4fe9d13 Mon Sep 17 00:00:00 2001
From: heisen-li <liziqiang5@huawei.com>
Date: Sun, 28 Apr 2024 17:03:01 +0800
Subject: [PATCH] fix(alias): Aliases without subcommands should not panic

---
 src/bin/cargo/cli.rs                  |  8 +++++++-
 tests/testsuite/cargo_alias_config.rs | 24 ++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/bin/cargo/cli.rs b/src/bin/cargo/cli.rs
index f4f04bb4f5e..de1653e39ad 100644
--- a/src/bin/cargo/cli.rs
+++ b/src/bin/cargo/cli.rs
@@ -356,7 +356,13 @@ For more information, see issue #12207 <https://github.com/rust-lang/cargo/issue
                 let global_args = GlobalArgs::new(sub_args);
                 let new_args = cli(gctx).no_binary_name(true).try_get_matches_from(alias)?;
 
-                let new_cmd = new_args.subcommand_name().expect("subcommand is required");
+                let Some(new_cmd) = new_args.subcommand_name() else {
+                    return Err(anyhow!(
+                        "subcommand is required, add a subcommand to the command alias `alias.{cmd}`"
+                    )
+                        .into());
+                };
+
                 already_expanded.push(cmd.to_string());
                 if already_expanded.contains(&new_cmd.to_string()) {
                     // Crash if the aliases are corecursive / unresolvable
diff --git a/tests/testsuite/cargo_alias_config.rs b/tests/testsuite/cargo_alias_config.rs
index 82b19254c0a..4ea188a8810 100644
--- a/tests/testsuite/cargo_alias_config.rs
+++ b/tests/testsuite/cargo_alias_config.rs
@@ -463,3 +463,27 @@ fn empty_alias() {
         )
         .run();
 }
+
+#[cargo_test]
+fn alias_no_subcommand() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            ".cargo/config.toml",
+            r#"
+               [alias]
+               a = "--locked"
+            "#,
+        )
+        .build();
+
+    p.cargo("a")
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] subcommand is required, add a subcommand to the command alias `alias.a`
+",
+        )
+        .run();
+}