Rollup merge of rust-lang#113518 - jyn514:streaming-failures, r=cuviper

bootstrap/libtest: print test name eagerly on failure even with `verbose-tests=false` / `--quiet`

Previously, libtest would wait until all tests finished running to print the progress, which made it
annoying to run many tests at once (since you don't know which have failed). Change it to print the
names as soon as they fail.

This makes it much easier to know which test failed without having to wait for compiletest to completely finish running. Before:
```
Testing stage0 compiletest suite=ui mode=ui (x86_64-unknown-linux-gnu)

running 15274 tests
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii    88/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   176/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   264/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   352/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   440/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   528/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiFFiiiiiii
...
```

After:
```
Testing stage0 compiletest suite=ui mode=ui (x86_64-unknown-linux-gnu)

running 15274 tests
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii    88/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   176/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   264/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   352/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   440/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii   528/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii
[ui] tests/ui/associated-type-bounds/implied-in-supertrait.rs ... F

[ui] tests/ui/associated-type-bounds/return-type-notation/basic.rs#next_with ... F
iiiiiiiiiiiii
...
```

This serves a similar use case to the existing RUSTC_TEST_FAIL_FAST, but is on by default and as a result much more discoverable. We should consider unifying RUSTC_TEST_FAIL_FAST with the `--no-fail-fast` flag in the future for consistency and discoverability.

Author: matthiaskrgr

test/src/formatters/terse.rs

@@ -23,6 +23,7 @@ pub(crate) struct TerseFormatter<T> {
     max_name_len: usize,
 
     test_count: usize,
+    test_column: usize,
     total_test_count: usize,
 }
 
@@ -39,6 +40,7 @@ impl<T: Write> TerseFormatter<T> {
             max_name_len,
             is_multithreaded,
             test_count: 0,
+            test_column: 0,
             total_test_count: 0, // initialized later, when write_run_start is called
         }
     }
@@ -47,8 +49,20 @@ impl<T: Write> TerseFormatter<T> {
         self.write_short_result(".", term::color::GREEN)
     }
 
-    pub fn write_failed(&mut self) -> io::Result<()> {
-        self.write_short_result("F", term::color::RED)
+    pub fn write_failed(&mut self, name: &str) -> io::Result<()> {
+        // Put failed tests on their own line and include the test name, so that it's faster
+        // to see which test failed without having to wait for them all to run.
+
+        // normally, we write the progress unconditionally, even if the previous line was cut short.
+        // but if this is the very first column, no short results will have been printed and we'll end up with *only* the progress on the line.
+        // avoid this.
+        if self.test_column != 0 {
+            self.write_progress()?;
+        }
+        self.test_count += 1;
+        self.write_plain(format!("{name} --- "))?;
+        self.write_pretty("FAILED", term::color::RED)?;
+        self.write_plain("\n")
     }
 
     pub fn write_ignored(&mut self) -> io::Result<()> {
@@ -65,15 +79,22 @@ impl<T: Write> TerseFormatter<T> {
         color: term::color::Color,
     ) -> io::Result<()> {
         self.write_pretty(result, color)?;
-        if self.test_count % QUIET_MODE_MAX_COLUMN == QUIET_MODE_MAX_COLUMN - 1 {
+        self.test_count += 1;
+        self.test_column += 1;
+        if self.test_column % QUIET_MODE_MAX_COLUMN == QUIET_MODE_MAX_COLUMN - 1 {
             // We insert a new line regularly in order to flush the
             // screen when dealing with line-buffered output (e.g., piping to
             // `stamp` in the rust CI).
-            let out = format!(" {}/{}\n", self.test_count + 1, self.total_test_count);
-            self.write_plain(out)?;
+            self.write_progress()?;
         }
 
-        self.test_count += 1;
+        Ok(())
+    }
+
+    fn write_progress(&mut self) -> io::Result<()> {
+        let out = format!(" {}/{}\n", self.test_count, self.total_test_count);
+        self.write_plain(out)?;
+        self.test_column = 0;
         Ok(())
     }
 
@@ -213,7 +234,7 @@ impl<T: Write> OutputFormatter for TerseFormatter<T> {
         match *result {
             TestResult::TrOk => self.write_ok(),
             TestResult::TrFailed | TestResult::TrFailedMsg(_) | TestResult::TrTimedFail => {
-                self.write_failed()
+                self.write_failed(desc.name.as_slice())
             }
             TestResult::TrIgnored => self.write_ignored(),
             TestResult::TrBench(ref bs) => {