feat(cli): warn when removing the last/host target for a toolchain

Cargo.toml

@@ -94,6 +94,7 @@ wait-timeout = "0.2"
 walkdir = { workspace = true, optional = true }
 xz2 = "0.1.3"
 zstd = "0.13"
+itertools = "0.12.0"
 
 [target."cfg(windows)".dependencies]
 cc = "1"

src/cli/rustup_mode.rs

@@ -10,6 +10,7 @@ use clap::{
  Arg, ArgAction, ArgGroup, ArgMatches, Command, ValueEnum,
 };
 use clap_complete::Shell;
+use itertools::Itertools;
 
 use crate::{
  cli::{
@@ -1334,11 +1335,22 @@ fn target_remove(cfg: &Cfg, m: &ArgMatches) -> Result<utils::ExitCode> {
  let distributable = DistributableToolchain::try_from(&toolchain)?;
 
  for target in m.get_many::<String>("target").unwrap() {
- let new_component = Component::new(
- "rust-std".to_string(),
- Some(TargetTriple::new(target)),
- false,
- );
+ let target = TargetTriple::new(target);
+ let default_target = cfg.get_default_host_triple().ok();
+ if default_target.as_ref() == Some(&target) {
+ warn!("after removing the default host target, proc-macros and build scripts might no longer build");
+ }
+ let at_most_one_target = distributable.components().ok().and_then(|cs| {
+ // Every component target that is not `None` (wildcard).
+ let targets = cs
+ .iter()
+ .filter_map(|c| c.installed.then(|| c.component.target.clone()).flatten());
+ targets.unique().at_most_one().ok()
+ });
+ if at_most_one_target.is_some() {
+ warn!("after removing the last target, no build targets will be available");
+ }
+ let new_component = Component::new("rust-std".to_string(), Some(target), false);
  distributable.remove_component(new_component)?;
  }
 

tests/suite/cli_v2.rs

@@ -952,9 +952,31 @@ fn remove_target_again() {
 #[test]
 fn remove_target_host() {
  setup(&|config| {
- let trip = this_host_triple();
+ let host = this_host_triple();
  config.expect_ok(&["rustup", "default", "nightly"]);
- config.expect_ok(&["rustup", "target", "remove", &trip]);
+ config.expect_ok(&["rustup", "target", "add", clitools::CROSS_ARCH1]);
+ config.expect_stderr_ok(
+ &["rustup", "target", "remove", &host], 
+ "after removing the default host target, proc-macros and build scripts might no longer build",
+ );
+ let path = format!("toolchains/nightly-{host}/lib/rustlib/{host}/lib/libstd.rlib");
+ assert!(!config.rustupdir.has(path));
+ let path = format!("toolchains/nightly-{host}/lib/rustlib/{host}/lib");
+ assert!(!config.rustupdir.has(path));
+ let path = format!("toolchains/nightly-{host}/lib/rustlib/{host}");
+ assert!(!config.rustupdir.has(path));
+ });
+}
+
+#[test]
+fn remove_target_last() {
+ setup(&|config| {
+ let host = this_host_triple();
+ config.expect_ok(&["rustup", "default", "nightly"]);
+ config.expect_stderr_ok(
+ &["rustup", "target", "remove", &host],
+ "after removing the last target, no build targets will be available",
+ );
  });
 }