test: Add test codebase for shell completions

Cargo.toml

@@ -36,7 +36,9 @@ cargo-util = { version = "0.2.14", path = "crates/cargo-util" }
 cargo-util-schemas = { version = "0.6.0", path = "crates/cargo-util-schemas" }
 cargo_metadata = "0.18.1"
 clap = "4.5.11"
+clap_complete = { version = "4.5.24", features = ["unstable-dynamic"] }
 color-print = "0.3.6"
+completest-pty = "0.5.3"
 core-foundation = { version = "0.10.0", features = ["mac_os_10_7_support"] }
 crates-io = { version = "0.40.4", path = "crates/crates-io" }
 criterion = { version = "0.5.1", features = ["html_reports"] }
@@ -153,6 +155,7 @@ cargo-platform.workspace = true
 cargo-util-schemas.workspace = true
 cargo-util.workspace = true
 clap = { workspace = true, features = ["wrap_help"] }
+clap_complete.workspace = true
 color-print.workspace = true
 crates-io.workspace = true
 curl = { workspace = true, features = ["http2"] }
@@ -239,6 +242,7 @@ features = [
 [dev-dependencies]
 annotate-snippets = { workspace = true, features = ["testing-colors"] }
 cargo-test-support.workspace = true
+completest-pty.workspace = true
 gix = { workspace = true, features = ["revision"] }
 same-file.workspace = true
 snapbox.workspace = true

tests/testsuite/main.rs

@@ -166,6 +166,7 @@ mod rustflags;
 mod rustup;
 mod script;
 mod search;
+mod shell_completions;
 mod shell_quoting;
 mod source_replacement;
 mod ssh;

tests/testsuite/shell_completions.rs

@@ -0,0 +1,56 @@
+use completest_pty::Runtime;
+
+fn complete(input: &str, shell: &str) -> String {
+    let shell = shell.into();
+
+    // Load the runtime
+    let mut runtime = match shell {
+        "bash" => load_runtime::<completest_pty::BashRuntimeBuilder>("bash"),
+        "elvish" => load_runtime::<completest_pty::ElvishRuntimeBuilder>("elvish"),
+        "fish" => load_runtime::<completest_pty::FishRuntimeBuilder>("fish"),
+        "zsh" => load_runtime::<completest_pty::ZshRuntimeBuilder>("zsh"),
+        _ => panic!("Unsupported shell: {}", shell),
+    };
+
+    // Exec the completion
+    let term = completest_pty::Term::new();
+    let actual = runtime.complete(input, &term).unwrap();
+
+    actual
+}
+
+// Return the scratch directory to keep it not being dropped
+fn load_runtime<R: completest_pty::RuntimeBuilder>(shell: &str) -> Box<dyn completest_pty::Runtime>
+where
+    <R as completest_pty::RuntimeBuilder>::Runtime: 'static,
+{
+    let home = cargo_test_support::paths::home();
+
+    let bin_path = cargo_test_support::cargo_exe();
+    let bin_root = bin_path.parent().unwrap().to_owned();
+
+    let mut runtime = Box::new(R::new(bin_root, home).unwrap());
+
+    match shell {
+        "bash" => runtime
+            .register("", "source <(CARGO_COMPLETE=bash cargo)")
+            .unwrap(),
+        "elvish" => runtime
+            .register("", "eval (E:CARGO_COMPLETE=elvish cargo | slurp)")
+            .unwrap(),
+        "fish" => runtime
+            .register("cargo", "source (CARGO_COMPLETE=fish cargo | psub)")
+            .unwrap(),
+        "zsh" => runtime
+            .register(
+                "cargo",
+                "#compdef cargo
+source <(CARGO_COMPLETE=zsh cargo)",
+            )
+            .unwrap(),
+        _ => panic!("Unsupported shell: {}", shell),
+    }
+
+    runtime
+}
+