Rollup merge of #113942 - ehuss:squelch-bad_path_expr_1, r=fee1-dead

Squelch a noisy rustc_expand unittest

The test `rustc_parse::tests::bad_path_expr_1` prints an error message to stderr, circumventing libtest's stderr intercept. This causes noise when running tests, in particular they show up 16 times on the GitHub Actions summary page. The solution here is to not use an error emitter that prints to stderr, and instead check that the correct error is generated.

2 files changed, 57 insertions, 24 deletions

diff --git a/compiler/rustc_expand/src/parse/tests.rs b/compiler/rustc_expand/src/parse/tests.rs
index 8b37728b60f..e133501c5d0 100644
--- a/compiler/rustc_expand/src/parse/tests.rs
+++ b/compiler/rustc_expand/src/parse/tests.rs
@@ -1,4 +1,6 @@
-use crate::tests::{matches_codepattern, string_to_stream, with_error_checking_parse};
+use crate::tests::{
+    matches_codepattern, string_to_stream, with_error_checking_parse, with_expected_parse_error,
+};
 
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token};
@@ -51,11 +53,15 @@ fn string_to_item(source_str: String) -> Option<P<ast::Item>> {
     with_error_checking_parse(source_str, &sess(), |p| p.parse_item(ForceCollect::No))
 }
 
-#[should_panic]
 #[test]
 fn bad_path_expr_1() {
+    // This should trigger error: expected identifier, found keyword `return`
     create_default_session_globals_then(|| {
-        string_to_expr("::abc::def::return".to_string());
+        with_expected_parse_error(
+            "::abc::def::return",
+            "expected identifier, found keyword `return`",
+            |p| p.parse_expr(),
+        );
     })
 }
 
diff --git a/compiler/rustc_expand/src/tests.rs b/compiler/rustc_expand/src/tests.rs
index aec0a1c6d8e..30fa5fea407 100644
--- a/compiler/rustc_expand/src/tests.rs
+++ b/compiler/rustc_expand/src/tests.rs
@@ -22,6 +22,33 @@ fn string_to_parser(ps: &ParseSess, source_str: String) -> Parser<'_> {
     new_parser_from_source_str(ps, PathBuf::from("bogofile").into(), source_str)
 }
 
+fn create_test_handler() -> (Handler, Lrc<SourceMap>, Arc<Mutex<Vec<u8>>>) {
+    let output = Arc::new(Mutex::new(Vec::new()));
+    let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+    let fallback_bundle = rustc_errors::fallback_fluent_bundle(
+        vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+        false,
+    );
+    let emitter = EmitterWriter::new(
+        Box::new(Shared { data: output.clone() }),
+        Some(source_map.clone()),
+        None,
+        fallback_bundle,
+        false,
+        false,
+        false,
+        Some(140),
+        false,
+        false,
+        TerminalUrl::No,
+    );
+    let handler = Handler::with_emitter(Box::new(emitter));
+    (handler, source_map, output)
+}
+
+/// Returns the result of parsing the given string via the given callback.
+///
+/// If there are any errors, this will panic.
 pub(crate) fn with_error_checking_parse<'a, T, F>(s: String, ps: &'a ParseSess, f: F) -> T
 where
     F: FnOnce(&mut Parser<'a>) -> PResult<'a, T>,
@@ -32,6 +59,26 @@ where
     x
 }
 
+/// Verifies that parsing the given string using the given callback will
+/// generate an error that contains the given text.
+pub(crate) fn with_expected_parse_error<T, F>(source_str: &str, expected_output: &str, f: F)
+where
+    F: for<'a> FnOnce(&mut Parser<'a>) -> PResult<'a, T>,
+{
+    let (handler, source_map, output) = create_test_handler();
+    let ps = ParseSess::with_span_handler(handler, source_map);
+    let mut p = string_to_parser(&ps, source_str.to_string());
+    let result = f(&mut p);
+    assert!(result.is_ok());
+
+    let bytes = output.lock().unwrap();
+    let actual_output = str::from_utf8(&bytes).unwrap();
+    println!("expected output:\n------\n{}------", expected_output);
+    println!("actual output:\n------\n{}------", actual_output);
+
+    assert!(actual_output.contains(expected_output))
+}
+
 /// Maps a string to tts, using a made-up filename.
 pub(crate) fn string_to_stream(source_str: String) -> TokenStream {
     let ps = ParseSess::new(
@@ -130,13 +177,7 @@ impl<T: Write> Write for Shared<T> {
 
 fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &str) {
     create_default_session_if_not_set_then(|_| {
-        let output = Arc::new(Mutex::new(Vec::new()));
-
-        let fallback_bundle = rustc_errors::fallback_fluent_bundle(
-            vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
-            false,
-        );
-        let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let (handler, source_map, output) = create_test_handler();
         source_map.new_source_file(Path::new("test.rs").to_owned().into(), file_text.to_owned());
 
         let primary_span = make_span(&file_text, &span_labels[0].start, &span_labels[0].end);
@@ -148,20 +189,6 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
             println!("text: {:?}", source_map.span_to_snippet(span));
         }
 
-        let emitter = EmitterWriter::new(
-            Box::new(Shared { data: output.clone() }),
-            Some(source_map.clone()),
-            None,
-            fallback_bundle,
-            false,
-            false,
-            false,
-            None,
-            false,
-            false,
-            TerminalUrl::No,
-        );
-        let handler = Handler::with_emitter(Box::new(emitter));
         #[allow(rustc::untranslatable_diagnostic)]
         handler.span_err(msp, "foo");