Auto merge of #118548 - Enselic:bench-padding, r=thomcc,ChrisDenton

libtest: Fix padding of benchmarks run as tests

### Summary

The first commit adds regression tests for libtest padding.

The second commit fixes padding for benches run as tests and updates the blessed output of the regression tests to make it clear what effect the fix has on padding.

Closes #104092 which is **E-help-wanted** and **regression-from-stable-to-stable**

### More details

Before this fix we applied padding _before_ manually doing what `convert_benchmarks_to_tests()` does which affects padding calculations. Instead use `convert_benchmarks_to_tests()` first if applicable and then apply padding afterwards so it becomes correct.

Benches should only be padded when run as benches to make it easy to compare the benchmark numbers. Not when run as tests.

r? `@ghost` until CI passes.

library/test/src/lib.rs

@@ -298,24 +298,18 @@ where
 
     let mut filtered = FilteredTests { tests: Vec::new(), benches: Vec::new(), next_id: 0 };
 
-    for test in filter_tests(opts, tests) {
+    let mut filtered_tests = filter_tests(opts, tests);
+    if !opts.bench_benchmarks {
+        filtered_tests = convert_benchmarks_to_tests(filtered_tests);
+    }
+
+    for test in filtered_tests {
         let mut desc = test.desc;
         desc.name = desc.name.with_padding(test.testfn.padding());
 
         match test.testfn {
-            DynBenchFn(benchfn) => {
-                if opts.bench_benchmarks {
-                    filtered.add_bench(desc, DynBenchFn(benchfn));
-                } else {
-                    filtered.add_test(desc, DynBenchAsTestFn(benchfn));
-                }
-            }
-            StaticBenchFn(benchfn) => {
-                if opts.bench_benchmarks {
-                    filtered.add_bench(desc, StaticBenchFn(benchfn));
-                } else {
-                    filtered.add_test(desc, StaticBenchAsTestFn(benchfn));
-                }
+            DynBenchFn(_) | StaticBenchFn(_) => {
+                filtered.add_bench(desc, test.testfn);
             }
             testfn => {
                 filtered.add_test(desc, testfn);

tests/run-make/libtest-padding/Makefile

@@ -0,0 +1,14 @@
+# ignore-cross-compile because we run the compiled code
+# needs-unwind because #[bench] and -Cpanic=abort requires -Zpanic-abort-tests
+include ../tools.mk
+
+NORMALIZE=sed 's%[0-9,]\{1,\} ns/iter (+/- [0-9,]\{1,\})%?? ns/iter (+/- ??)%' | sed 's%finished in [0-9\.]\{1,\}%finished in ??%'
+
+all:
+	$(RUSTC) --test tests.rs
+
+	$(call RUN,tests) --test-threads=1 | $(NORMALIZE) > "$(TMPDIR)"/test.stdout
+	$(RUSTC_TEST_OP) "$(TMPDIR)"/test.stdout test.stdout
+
+	$(call RUN,tests) --test-threads=1 --bench | $(NORMALIZE) > "$(TMPDIR)"/bench.stdout
+	$(RUSTC_TEST_OP) "$(TMPDIR)"/bench.stdout bench.stdout

tests/run-make/libtest-padding/bench.stdout

@@ -0,0 +1,9 @@
+
+running 4 tests
+test short_test_name ... ignored
+test this_is_a_really_long_test_name ... ignored
+test short_bench_name                 ... bench:           ?? ns/iter (+/- ??)
+test this_is_a_really_long_bench_name ... bench:           ?? ns/iter (+/- ??)
+
+test result: ok. 0 passed; 0 failed; 2 ignored; 2 measured; 0 filtered out; finished in ??s
+

tests/run-make/libtest-padding/test.stdout

@@ -0,0 +1,9 @@
+
+running 4 tests
+test short_bench_name ... ok
+test short_test_name ... ok
+test this_is_a_really_long_bench_name ... ok
+test this_is_a_really_long_test_name ... ok
+
+test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in ??s
+

tests/run-make/libtest-padding/tests.rs

@@ -0,0 +1,18 @@
+#![feature(test)]
+extern crate test;
+
+#[test]
+fn short_test_name() {}
+
+#[test]
+fn this_is_a_really_long_test_name() {}
+
+#[bench]
+fn short_bench_name(b: &mut test::Bencher) {
+    b.iter(|| 1);
+}
+
+#[bench]
+fn this_is_a_really_long_bench_name(b: &mut test::Bencher) {
+    b.iter(|| 1);
+}