Auto merge of #14548 - shannmu:_cargo_test_names, r=epage

feat: Add custom completer for completing test names

### What does this PR try to resolve?
Tracking issue #14520

Add custom completer for `cargo test --test <TAB>`

src/cargo/util/command_prelude.rs

@@ -156,7 +156,11 @@ pub trait CommandExt: Sized {
  ) -> Self {
  self.arg_targets_lib_bin_example(lib, bin, bins, example, examples)
  ._arg(flag("tests", tests).help_heading(heading::TARGET_SELECTION))
- ._arg(optional_multi_opt("test", "NAME", test).help_heading(heading::TARGET_SELECTION))
+ ._arg(
+ optional_multi_opt("test", "NAME", test)
+ .help_heading(heading::TARGET_SELECTION)
+ .add(clap_complete::ArgValueCandidates::new(get_test_candidates)),
+ )
  ._arg(flag("benches", benches).help_heading(heading::TARGET_SELECTION))
  ._arg(
  optional_multi_opt("bench", "NAME", bench).help_heading(heading::TARGET_SELECTION),
@@ -1042,6 +1046,17 @@ pub fn lockfile_path(
  return Ok(Some(path));
 }
 
+fn get_test_candidates() -> Vec<clap_complete::CompletionCandidate> {
+ get_targets_from_metadata()
+ .unwrap_or_default()
+ .into_iter()
+ .filter_map(|target| match target.kind() {
+ TargetKind::Test => Some(clap_complete::CompletionCandidate::new(target.name())),
+ _ => None,
+ })
+ .collect::<Vec<_>>()
+}
+
 fn get_bin_candidates() -> Vec<clap_complete::CompletionCandidate> {
  get_targets_from_metadata()
  .unwrap_or_default()