Auto merge of #14533 - shannmu:_bin_names, r=epage

feat: Add custom completer for completing bin names

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

Add custom completer for `cargo build --bin=<TAB>`

Author: bors

src/cargo/util/command_prelude.rs

@@ -1,6 +1,6 @@
 use crate::core::compiler::{BuildConfig, MessageFormat, TimingOutput};
 use crate::core::resolver::CliFeatures;
-use crate::core::{Edition, Workspace};
+use crate::core::{shell, Edition, Target, TargetKind, Workspace};
 use crate::ops::lockfile::LOCKFILE_NAME;
 use crate::ops::registry::RegistryOrIndex;
 use crate::ops::{CompileFilter, CompileOptions, NewOptions, Packages, VersionControl};
@@ -19,6 +19,7 @@ use cargo_util_schemas::manifest::ProfileName;
 use cargo_util_schemas::manifest::RegistryName;
 use cargo_util_schemas::manifest::StringOrVec;
 use clap::builder::UnknownArgumentValueParser;
+use home::cargo_home_with_cwd;
 use std::ffi::{OsStr, OsString};
 use std::path::Path;
 use std::path::PathBuf;
@@ -173,7 +174,11 @@ pub trait CommandExt: Sized {
     ) -> Self {
         self._arg(flag("lib", lib).help_heading(heading::TARGET_SELECTION))
             ._arg(flag("bins", bins).help_heading(heading::TARGET_SELECTION))
-            ._arg(optional_multi_opt("bin", "NAME", bin).help_heading(heading::TARGET_SELECTION))
+            ._arg(
+                optional_multi_opt("bin", "NAME", bin)
+                    .help_heading(heading::TARGET_SELECTION)
+                    .add(clap_complete::ArgValueCandidates::new(get_bin_candidates)),
+            )
             ._arg(flag("examples", examples).help_heading(heading::TARGET_SELECTION))
             ._arg(
                 optional_multi_opt("example", "NAME", example)
@@ -188,21 +193,27 @@ pub trait CommandExt: Sized {
         example: &'static str,
         examples: &'static str,
     ) -> Self {
-        self._arg(optional_multi_opt("bin", "NAME", bin).help_heading(heading::TARGET_SELECTION))
-            ._arg(flag("bins", bins).help_heading(heading::TARGET_SELECTION))
-            ._arg(
-                optional_multi_opt("example", "NAME", example)
-                    .help_heading(heading::TARGET_SELECTION),
-            )
-            ._arg(flag("examples", examples).help_heading(heading::TARGET_SELECTION))
+        self._arg(
+            optional_multi_opt("bin", "NAME", bin)
+                .help_heading(heading::TARGET_SELECTION)
+                .add(clap_complete::ArgValueCandidates::new(get_bin_candidates)),
+        )
+        ._arg(flag("bins", bins).help_heading(heading::TARGET_SELECTION))
+        ._arg(
+            optional_multi_opt("example", "NAME", example).help_heading(heading::TARGET_SELECTION),
+        )
+        ._arg(flag("examples", examples).help_heading(heading::TARGET_SELECTION))
     }
 
     fn arg_targets_bin_example(self, bin: &'static str, example: &'static str) -> Self {
-        self._arg(optional_multi_opt("bin", "NAME", bin).help_heading(heading::TARGET_SELECTION))
-            ._arg(
-                optional_multi_opt("example", "NAME", example)
-                    .help_heading(heading::TARGET_SELECTION),
-            )
+        self._arg(
+            optional_multi_opt("bin", "NAME", bin)
+                .help_heading(heading::TARGET_SELECTION)
+                .add(clap_complete::ArgValueCandidates::new(get_bin_candidates)),
+        )
+        ._arg(
+            optional_multi_opt("example", "NAME", example).help_heading(heading::TARGET_SELECTION),
+        )
     }
 
     fn arg_features(self) -> Self {
@@ -333,7 +344,10 @@ pub trait CommandExt: Sized {
             .value_name("VCS")
             .value_parser(["git", "hg", "pijul", "fossil", "none"]),
         )
-        ._arg(flag("bin", "Use a binary (application) template [default]"))
+        ._arg(
+            flag("bin", "Use a binary (application) template [default]")
+                .add(clap_complete::ArgValueCandidates::new(get_bin_candidates)),
+        )
         ._arg(flag("lib", "Use a library template"))
         ._arg(
             opt("edition", "Edition to set for the crate generated")
@@ -1027,6 +1041,32 @@ pub fn lockfile_path(
     return Ok(Some(path));
 }
 
+fn get_bin_candidates() -> Vec<clap_complete::CompletionCandidate> {
+    get_targets_from_metadata()
+        .unwrap_or_default()
+        .into_iter()
+        .filter_map(|target| match target.kind() {
+            TargetKind::Bin => Some(clap_complete::CompletionCandidate::new(target.name())),
+            _ => None,
+        })
+        .collect::<Vec<_>>()
+}
+
+fn get_targets_from_metadata() -> CargoResult<Vec<Target>> {
+    let cwd = std::env::current_dir()?;
+    let gctx = GlobalContext::new(shell::Shell::new(), cwd.clone(), cargo_home_with_cwd(&cwd)?);
+    let ws = Workspace::new(&find_root_manifest_for_wd(&cwd)?, &gctx)?;
+
+    let packages = ws.members().collect::<Vec<_>>();
+
+    let targets = packages
+        .into_iter()
+        .flat_map(|pkg| pkg.targets().into_iter().cloned())
+        .collect::<Vec<_>>();
+
+    Ok(targets)
+}
+
 #[track_caller]
 pub fn ignore_unknown<T: Default>(r: Result<T, clap::parser::MatchesError>) -> T {
     match r {