feat: Add custom completer for cargo <TAB> to complete aliases defined in config.toml

Author: nooma-42

src/bin/cargo/cli.rs

@@ -691,11 +691,13 @@ See '<cyan,bold>cargo help</> <cyan><<command>></>' for more information on a sp
                 }))
             }).collect()
         })))
-        .add(clap_complete::engine::SubcommandCandidates::new(|| {
-            get_toolchains_from_rustup()
+        .add(clap_complete::engine::SubcommandCandidates::new(move || {
+            let mut candidates = get_toolchains_from_rustup()
                 .into_iter()
                 .map(|t| clap_complete::CompletionCandidate::new(t))
-                .collect()
+                .collect::<Vec<_>>();
+            candidates.extend(crate::util::command_prelude::get_alias_candidates());
+            candidates
         }))
         .subcommands(commands::builtin())
 }

src/bin/cargo/main.rs

@@ -6,7 +6,6 @@ use cargo::util::network::http::http_handle;
 use cargo::util::network::http::needs_custom_http_transport;
 use cargo::util::{self, closest_msg, command_prelude, CargoResult};
 use cargo_util::{ProcessBuilder, ProcessError};
-use cargo_util_schemas::manifest::StringOrVec;
 use std::collections::BTreeMap;
 use std::env;
 use std::ffi::OsStr;
@@ -205,7 +204,7 @@ fn list_commands(gctx: &GlobalContext) -> BTreeMap<String, CommandInfo> {
     }
 
     // Add the user-defined aliases
-    let alias_commands = user_defined_aliases(gctx);
+    let alias_commands = command_prelude::user_defined_aliases(gctx);
     commands.extend(alias_commands);
 
     // `help` is special, so it needs to be inserted separately.
@@ -249,22 +248,6 @@ fn third_party_subcommands(gctx: &GlobalContext) -> BTreeMap<String, CommandInfo
     }
     commands
 }
-
-fn user_defined_aliases(gctx: &GlobalContext) -> BTreeMap<String, CommandInfo> {
-    let mut commands = BTreeMap::new();
-    if let Ok(aliases) = gctx.get::<BTreeMap<String, StringOrVec>>("alias") {
-        for (name, target) in aliases.iter() {
-            commands.insert(
-                name.to_string(),
-                CommandInfo::Alias {
-                    target: target.clone(),
-                },
-            );
-        }
-    }
-    commands
-}
-
 fn find_external_subcommand(gctx: &GlobalContext, cmd: &str) -> Option<PathBuf> {
     let command_exe = format!("cargo-{}{}", cmd, env::consts::EXE_SUFFIX);
     search_directories(gctx)

src/cargo/util/command_prelude.rs

@@ -24,7 +24,7 @@ use cargo_util_schemas::manifest::StringOrVec;
 use clap::builder::UnknownArgumentValueParser;
 use home::cargo_home_with_cwd;
 use semver::Version;
-use std::collections::HashMap;
+use std::collections::{BTreeMap, HashMap};
 use std::ffi::{OsStr, OsString};
 use std::path::Path;
 use std::path::PathBuf;
@@ -1370,6 +1370,50 @@ fn new_gctx_for_completions() -> CargoResult<GlobalContext> {
     Ok(gctx)
 }
 
+pub fn get_alias_candidates() -> Vec<clap_complete::CompletionCandidate> {
+    if let Ok(gctx) = new_gctx_for_completions() {
+        let alias_map = user_defined_aliases(&gctx);
+        return alias_map
+            .iter()
+            .map(|(alias, cmd_info)| {
+                let help_text = match cmd_info {
+                    CommandInfo::Alias { target } => {
+                        let cmd_str = target
+                            .iter()
+                            .map(String::as_str)
+                            .collect::<Vec<_>>()
+                            .join(" ");
+                        format!("alias for {}", cmd_str)
+                    }
+                    CommandInfo::BuiltIn { .. } => {
+                        unreachable!("BuiltIn command shouldn't appear in alias map")
+                    }
+                    CommandInfo::External { .. } => {
+                        unreachable!("External command shouldn't appear in alias map")
+                    }
+                };
+                clap_complete::CompletionCandidate::new(alias.clone()).help(Some(help_text.into()))
+            })
+            .collect();
+    }
+    Vec::new()
+}
+
+pub fn user_defined_aliases(gctx: &GlobalContext) -> BTreeMap<String, CommandInfo> {
+    let mut commands = BTreeMap::new();
+    if let Ok(aliases) = gctx.get::<BTreeMap<String, StringOrVec>>("alias") {
+        for (name, target) in aliases.iter() {
+            commands.insert(
+                name.to_string(),
+                CommandInfo::Alias {
+                    target: target.clone(),
+                },
+            );
+        }
+    }
+    commands
+}
+
 #[track_caller]
 pub fn ignore_unknown<T: Default>(r: Result<T, clap::parser::MatchesError>) -> T {
     match r {