Add tests for invoking multiple help options at once

Author: jamie-osec

tests/run-make/rustc-help/rmake.rs

@@ -18,4 +18,31 @@ fn main() {
     // Check the diff between `rustc --help` and `rustc --help -v`.
     let help_v_diff = similar::TextDiff::from_lines(&help, &help_v).unified_diff().to_string();
     diff().expected_file("help-v.diff").actual_text("actual", &help_v_diff).run();
+
+    // Check that all help options can be invoked at once
+    let codegen_help = bare_rustc().arg("-Chelp").run().stdout_utf8();
+    let unstable_help = bare_rustc().arg("-Zhelp").run().stdout_utf8();
+    let lints_help = bare_rustc().arg("-Whelp").run().stdout_utf8();
+    let expected_all = format!("{help}{codegen_help}{unstable_help}{lints_help}");
+    let all_help = bare_rustc().args(["--help", "-Chelp", "-Zhelp", "-Whelp"]).run().stdout_utf8();
+    diff()
+        .expected_text(
+            "(rustc --help && rustc -Chelp && rustc -Zhelp && rustc -Whelp)",
+            &expected_all,
+        )
+        .actual_text("(rustc --help -Chelp -Zhelp -Whelp)", &all_help)
+        .run();
+
+    // Check that the ordering of help options is respected
+    // Note that this is except for `-Whelp`, which always comes last
+    let expected_ordered_help = format!("{unstable_help}{codegen_help}{help}{lints_help}");
+    let ordered_help =
+        bare_rustc().args(["-Whelp", "-Zhelp", "-Chelp", "--help"]).run().stdout_utf8();
+    diff()
+        .expected_text(
+            "(rustc -Whelp && rustc -Zhelp && rustc -Chelp && rustc --help)",
+            &expected_ordered_help,
+        )
+        .actual_text("(rustc -Whelp -Zhelp -Chelp --help)", &ordered_help)
+        .run();
 }