doctests: print_merged_doctests_times() crashes JUnit formatter #149436
Description
When unstable --format=junit is used, crates with doctests panic.
Code
/// ``` /// assert_eq!(2 + 2, 4); /// ``` pub fn foo() {}cargo test --doc -- -Z unstable-options --format=junit Meta
rustc --version --verbose:
rustc 1.92.0-nightly (6501e64fc 2025-10-23) binary: rustc commit-hash: 6501e64fcb02d22b49d6e59d10a7692ec8095619 commit-date: 2025-10-23 host: aarch64-apple-darwin release: 1.92.0-nightly LLVM version: 21.1.3 Error output
thread 'main' (59091947) panicked at library/test/src/formatters/junit.rs:22:9: assertion failed: !s.contains('\n') Backtrace
stack backtrace: 0: 0x1117b9284 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::heca2c53e567951af 1: 0x10ebfc128 - core::fmt::write::hfd392e77bbd0a117 2: 0x1117722f4 - std::io::Write::write_fmt::h2e5d5d3b14293b5d 3: 0x1117844a8 - std::sys::backtrace::BacktraceLock::print::haf2c31c8f0b66728 4: 0x11178ad2c - std::panicking::default_hook::{{closure}}::hb6a1626dcc9d638e 5: 0x11178a9cc - std::panicking::default_hook::he558bb5633d06dd3 6: 0x10f7a6c2c - std[31820d8d119d2b1a]::panicking::update_hook::<alloc[c98364d87502df1f]::boxed::Box<rustc_driver_impl[741f0d247cd92ffe]::install_ice_hook::{closure#1}>>::{closure#0} 7: 0x11178b254 - std::panicking::panic_with_hook::h9fbd4402ab35bb12 8: 0x11178aedc - std::panicking::panic_handler::{{closure}}::hdc508ac937b59f80 9: 0x1117845c0 - std::sys::backtrace::__rust_end_short_backtrace::h1152a0393351b73f 10: 0x111768a7c - __rustc[4683036c762297f9]::rust_begin_unwind 11: 0x1144f1d6c - core::panicking::panic_fmt::hd6f40ed356ee47b2 12: 0x1144f1d4c - core::panicking::panic::h2db8414143ce2846 13: 0x102e9e5b4 - <test::formatters::junit::JunitFormatter<T> as test::formatters::OutputFormatter>::write_merged_doctests_times::ha74d38c005789c1e 14: 0x102eb526c - test::print_merged_doctests_times::hdcdf0fdad92fc855 15: 0x102d665e0 - rustdoc[fc49a747f52601b2]::doctest::run_tests 16: 0x102d62720 - rustdoc[fc49a747f52601b2]::doctest::run 17: 0x102ca505c - rustdoc[fc49a747f52601b2]::main_args 18: 0x102ca0a74 - rustdoc[fc49a747f52601b2]::main 19: 0x102e86fc4 - std[31820d8d119d2b1a]::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()> 20: 0x102e86fdc - std[31820d8d119d2b1a]::rt::lang_start::<()>::{closure#0} 21: 0x1117750fc - std::rt::lang_start_internal::h8bc1be803cf24ab7 22: 0x102e8703c - _main