feat: Add native completions with CompleteEnv and under the nightly…

… features

src/bin/cargo/main.rs

@@ -1,5 +1,6 @@
 #![allow(clippy::self_named_module_files)] // false positive in `commands/build.rs`
 
+use cargo::core::features;
 use cargo::core::shell::Shell;
 use cargo::util::network::http::http_handle;
 use cargo::util::network::http::needs_custom_http_transport;
@@ -28,6 +29,13 @@ fn main() {
         }
     };
 
+    let nightly_features_allowed = matches!(&*features::channel(), "nightly" | "dev");
+    if nightly_features_allowed {
+        clap_complete::CompleteEnv::with_factory(|| cli::cli(&mut gctx))
+            .var("CARGO_COMPLETE")
+            .complete();
+    }
+
     let result = if let Some(lock_addr) = cargo::ops::fix_get_proxy_lock_addr() {
         cargo::ops::fix_exec_rustc(&gctx, &lock_addr).map_err(|e| CliError::from(e))
     } else {

src/doc/src/reference/unstable.md

@@ -116,6 +116,7 @@ Each new feature described below should explain how to use it.
     * [gitoxide](#gitoxide) --- Use `gitoxide` instead of `git2` for a set of operations.
     * [script](#script) --- Enable support for single-file `.rs` packages.
     * [lockfile-path](#lockfile-path) --- Allows to specify a path to lockfile other than the default path `<workspace_root>/Cargo.lock`.
+    * [native-completions](#native-completion) --- Move cargo shell completions to native completions
 
 ## allow-features
 
@@ -1643,6 +1644,27 @@ Example:
 cargo +nightly metadata --lockfile-path=$LOCKFILES_ROOT/my-project/Cargo.lock -Z unstable-options
 ```
 
+## native-completions
+* Original Issue: [#6645](https://github.com/rust-lang/cargo/issues/6645)
+* Tracking Issue: [#14520](https://github.com/rust-lang/cargo/issues/14520)
+
+This feature moves the handwritten completion scripts to Rust native, making it
+easier for us to add, extend and test new completions. This feature is enabled with the
+nightly channel, without requiring additional `-Z` options.
+
+### How to use native-completions feature:
+- bash:
+  Add `source <(CARGO_COMPLETE=bash cargo)` to your .bashrc.
+
+- zsh:
+  Add `source <(CARGO_COMPLETE=zsh cargo)` to your .zshrc.
+
+- fish:
+  Add `source (CARGO_COMPLETE=fish cargo | psub)` to `$XDG_CONFIG_HOME/fish/completions/cargo.fish`
+
+- elvish:
+  Add `eval (E:CARGO_COMPLETE=elvish cargo | slurp)` to `$XDG_CONFIG_HOME/elvish/rc.elv`
+
 # Stabilized and removed features
 
 ## Compile progress

tests/testsuite/shell_completions/bash.rs

@@ -0,0 +1,24 @@
+use cargo_test_support::cargo_test;
+use snapbox::assert_data_eq;
+
+use crate::shell_completions;
+
+#[cargo_test]
+fn test_register_native_completions() {
+    let input = "cargo \t\t";
+    let expected = snapbox::str![
+        "% 
+--version          --help             check              install            read-manifest      update
+--list             -V                 clean              locate-project     remove             vendor
+--explain          -v                 config             login              report             verify-project
+--verbose          -q                 doc                logout             run                version
+--quiet            -C                 fetch              metadata           rustc              yank
+--color            -Z                 fix                new                rustdoc            
+--locked           -h                 generate-lockfile  owner              search             
+--offline          add                help               package            test               
+--frozen           bench              info               pkgid              tree               
+--config           build              init               publish            uninstall          "
+    ];
+    let actual = shell_completions::common::complete(input, "bash");
+    assert_data_eq!(actual, expected);
+}

tests/testsuite/shell_completions/elvish.rs

@@ -0,0 +1,25 @@
+use cargo_test_support::cargo_test;
+use snapbox::assert_data_eq;
+
+use crate::shell_completions;
+
+#[cargo_test]
+fn test_register_native_completions() {
+    let input = "cargo \t\t";
+    let expected = snapbox::str![
+        "% cargo
+COMPLETING argument  
+--color    --version  check              install         read-manifest  update        
+--config   -C         clean              locate-project  remove         vendor        
+--explain  -V         config             login           report         verify-project
+--frozen   -Z         doc                logout          run            version       
+--help     -h         fetch              metadata        rustc          yank          
+--list     -q         fix                new             rustdoc      
+--locked   -v         generate-lockfile  owner           search       
+--offline  add        help               package         test         
+--quiet    bench      info               pkgid           tree         
+--verbose  build      init               publish         uninstall    "
+    ];
+    let actual = shell_completions::common::complete(input, "elvish");
+    assert_data_eq!(actual, expected);
+}

tests/testsuite/shell_completions/fish.rs

@@ -0,0 +1,69 @@
+use cargo_test_support::cargo_test;
+use snapbox::assert_data_eq;
+
+use crate::shell_completions;
+
+#[cargo_test]
+fn test_register_native_completions() {
+    let input = "cargo \t\t";
+    let expected = snapbox::str![
+        "% cargo
+--version                                                                                  (Print version info and exit)
+--list                                                                                         (List installed commands)
+--explain                                                      (Provide a detailed explanation of a rustc error message)
+--verbose                                                        (Use verbose output (-vv very verbose/build.rs output))
+--quiet                                                                                (Do not print cargo log messages)
+--color                                                                                  (Coloring: auto, always, never)
+--locked                                                                (Assert that `Cargo.lock` will remain unchanged)
+--offline                                                                            (Run without accessing the network)
+--frozen                                                          (Equivalent to specifying both --locked and --offline)
+--config                                                                                (Override a configuration value)
+--help                                                                                                      (Print help)
+-V                                                                                         (Print version info and exit)
+-v                                                               (Use verbose output (-vv very verbose/build.rs output))
+-q                                                                                     (Do not print cargo log messages)
+-C                                                            (Change to DIRECTORY before doing anything (nightly-only))
+-Z                                             (Unstable (nightly-only) flags to Cargo, see 'cargo -Z help' for details)
+-h                                                                                                          (Print help)
+add                                                                     (Add dependencies to a Cargo.toml manifest file)
+bench                                                                        (Execute all benchmarks of a local package)
+build                                                              (Compile a local package and all of its dependencies)
+check                                                     (Check a local package and all of its dependencies for errors)
+clean                                                            (Remove artifacts that cargo has generated in the past)
+config                                                                                    (Inspect configuration values)
+doc                                                                                    (Build a package's documentation)
+fetch                                                                 (Fetch dependencies of a package from the network)
+fix                                                                  (Automatically fix lint warnings reported by rustc)
+generate-lockfile                                                                  (Generate the lockfile for a package)
+help                                                                              (Displays help for a cargo subcommand)
+info                                                               (Display information about a package in the registry)
+init                                                               (Create a new cargo package in an existing directory)
+install                                                                                          (Install a Rust binary)
+locate-project                                             (Print a JSON representation of a Cargo.toml file's location)
+login                                                                                            (Log in to a registry.)
+logout                                                                   (Remove an API token from the registry locally)
+metadata  (Output the resolved dependencies of a package, the concrete used versions including overrides, in machine-r…)
+new                                                                               (Create a new cargo package at <path>)
+owner                                                                     (Manage the owners of a crate on the registry)
+package                                                        (Assemble the local package into a distributable tarball)
+pkgid                                                                    (Print a fully qualified package specification)
+publish                                                                               (Upload a package to the registry)
+read-manifest                                                    (Print a JSON representation of a Cargo.toml manifest.)
+remove                                                             (Remove dependencies from a Cargo.toml manifest file)
+report                                                                   (Generate and display various kinds of reports)
+run                                                                       (Run a binary or example of the local package)
+rustc                                                        (Compile a package, and pass extra options to the compiler)
+rustdoc                                                 (Build a package's documentation, using specified custom flags.)
+search                                                  (Search packages in the registry. Default registry is crates.io)
+test                                      (Execute all unit and integration tests and build examples of a local package)
+tree                                                                (Display a tree visualization of a dependency graph)
+uninstall                                                                                         (Remove a Rust binary)
+update                                                          (Update dependencies as recorded in the local lock file)
+vendor                                                                   (Vendor all dependencies for a project locally)
+verify-project                                                                     (Check correctness of crate manifest)
+version                                                                                       (Show version information)
+yank                                                                              (Remove a pushed crate from the index)"];
+
+    let actual = shell_completions::common::complete(input, "fish");
+    assert_data_eq!(actual, expected);
+}

tests/testsuite/shell_completions/mod.rs

@@ -1,2 +1,6 @@
 pub mod common;
 
+mod bash;
+mod elvish;
+mod fish;
+mod zsh;

tests/testsuite/shell_completions/zsh.rs

@@ -0,0 +1,24 @@
+use cargo_test_support::cargo_test;
+use snapbox::assert_data_eq;
+
+use crate::shell_completions;
+
+#[cargo_test]
+fn test_register_native_completions() {
+    let input = "cargo \t\t";
+    let expected = snapbox::str![
+        "% cargo
+--color            --version          check              install            read-manifest      update
+--config           -C                 clean              locate-project     remove             vendor
+--explain          -V                 config             login              report             verify-project
+--frozen           -Z                 doc                logout             run                version
+--help             -h                 fetch              metadata           rustc              yank
+--list             -q                 fix                new                rustdoc            
+--locked           -v                 generate-lockfile  owner              search             
+--offline          add                help               package            test               
+--quiet            bench              info               pkgid              tree               
+--verbose          build              init               publish            uninstall          "
+    ];
+    let actual = shell_completions::common::complete(input, "zsh");
+    assert_data_eq!(actual, expected);
+}