# cargo-mutants changelog
## Unreleased
- Fixed support for the Mold linker, or for other options passed via `RUSTFLAGS` or `CARGO_ENCODED_RUSTFLAGS`. (See the instructions in README.md).
- Source trees are walked by following `mod` statements rather than globbing the directory. This is more correct if there are files that are not referenced by `mod` statements. Once attributes on modules are stable in Rust (<https://github.com/rust-lang/rust/issues/54727>) this opens a path to skip mods using attributes.
## 1.1.0
Released 2022-10-30
*Fearless concurrency!*
- cargo-mutants can now run multiple cargo build and test tasks in parallel, to make better use of machine resources and find mutants faster, controlled by `--jobs`.
- The minimum Rust version to build cargo-mutants is now 1.63.0. It can still be used to test code under older toolchains.
## 1.0.3
Released 2022-09-29
- cargo-mutants is now finds no uncaught mutants in itself! Various tests were added and improved, particularly around handling timeouts.
- New: `--re` and `--exclude-re` options to filter by mutant name, including the path. The regexps match against the strings printed by `--list`.
## 1.0.2
Released 2022-09-24
- New: `cargo mutants --completions SHELL` to generate shell completions using `clap_complete`.
- Changed: `carg-mutants` no longer builds in the source directory, and no longer copies the `target/` directory to the scratch directory. Since `cargo-mutants` now sets `RUSTFLAGS` to avoid false failures from warnings, it is unlikely to match the existing build products in the source directory `target/`, and in fact building there is just likely to cause rebuilds in the source. The behavior now is as if `--no-copy-target` was always passed. That option is still accepted, but it has no effect.
- Changed: `cargo-mutants` finds all possible mutations before doing the baseline test, so that you can see earlier how many there will be.
- New: Set `INSTA_UPDATE=no` so that tests that use the [Insta](https://insta.rs/) library don't write updates back into the source directory, and so don't falsely pass.
## 1.0.1
Released 2022-09-12
- Fixed: Don't try to mutate functions within test targets, e.g. within `tests/**/*.rs`.
- New: `missed.txt`, `caught.txt`, `timeout.txt` and `unviable.txt` files are written in to the output directory to make results easier to review later.
- New: `--output` creates the specified directory if it does not exist.
- Internal: Switched from Argh to Clap for command-line parsing. There may be some small changes in CLI behavior and help formatting.
## 1.0.0
Released 2022-08-21
A 1.0 release to celebrate that with the addition of workspace handling, cargo-mutants gives useful results on many Rust projects.
- New: Supports workspaces containing multiple packages. Mutants are generated for all relevant targets in all packages, and mutants are subject to the tests of their own package. `cargo mutants --list-files --json` and `cargo mutants --list --json` now includes package names for each file or mutant.
- Improved: Generate mutations in `cdylib`, `rlib`, and ever other `*lib` target. For example, this correctly exercises Wasm projects.
- Improved: Write `mutants.out/outcomes.json` after the source-tree build and baseline tests so that it can be observed earlier on.
- Improved: `mutants.out/outcomes.json` includes the commands run.
## 0.2.11
Released 2022-08-20
- New `--exclude` command line option to exclude source files from mutants generation, matching a glob.
- New: `CARGO_MUTANTS_MINIMUM_TEST_TIMEOUT` sets a minimum timeout for cargo tests, in seconds. This can be used to allow more time on slow CI builders. If unset the default is still 20s.
- Added: A new `mutants.out/debug.log` with internal debugging information.
- Improved: The time for check, build, and test is now shown separately in progress bars and output, to give a better indication of which is taking more time in the tree under test. Also, times are show in seconds with one decimal place, and they are styled more consistently.
- Improved: More consistent use of 'unviable' and other terms for outcomes in the UI.
## 0.2.10
Released 2022-08-07
cargo-mutants 0.2.10 comes with improved docs, and the new `-C` option can be used to pass options like `--release` or `--all-features` to `cargo`.
- Added: `--cargo-arg` (or `-C` for short) allows passing arguments to cargo commands (check, build, and test), for example to set `--release` or `--features`.
- Improved: Works properly if run from a subdirectory of a crate, or if `-d` points to a
subdirectory of a crate.
- Improved: Various docs.
- Improved: Relative dependencies within the source tree are left as relative paths, and will be built within the scratch directory. Relative dependencies outside the source tree are still rewritten as absolute paths.
## 0.2.9
Released 2022-07-30
- Faster: `cargo mutants` no longer runs `cargo check` before building, in cases where the build products are wanted or tests will be run. This saves a significant amount of work in build phases; in some trees `cargo mutants` is now 30% faster. (In trees where most of the time is spent running tests the effect will be less.)
- Fixed: Open log files in append mode to fix messages from other processes
occasionally being partly overwritten.
- Improved: `cargo mutants` should now give useful results in packages that use `#![deny(unused)]` or other mechanisms to reject warnings. Mutated functions often ignore some parameters, which would previously be rejected by this configuration without proving anything interesting about test coverage. Now, `--cap-lints=allow` is passed in `RUSTFLAGS` while building mutants, so that they're not falsely rejected and the tests can be exercised.
- Improved: The build dir name includes the root package name.
- Improved: The progress bar shows more information.
- Improved: The final message shows how many mutants were tested and how long it took.
## 0.2.8
Released 2022-07-18
- New: Summarize the overall number of mutants generated, caught, missed, etc, at the end.
- Fixed: Works properly with crates that have relative `path` dependencies in `Cargo.toml` or `.cargo/config.toml`, by rewriting them to absolute paths in the scratch directory.
## 0.2.7
Released 2022-07-11
- New: You can skip functions by adding `#[cfg_attr(test, mutants::skip)`, in which case the `mutants` crate can be only a `dev-dependency`.
- Improved: Don't generate pointless mutations of functions with an empty body (ignoring comments.)
- Improved: Remove extra whitespace from the display of function names and return types: the new formatting is closer to the spacing used in idiomatic Rust.
- Improved: Show the last line of compiler/test output while running builds, so that it's more clear where time is being spent.
- Docs: Instructions on how to check for missed mutants from CI.
## 0.2.6
Released 2022-04-17
- Improved: Find source files by looking at `cargo metadata` output, rather than
assuming they're in `src/**/*.rs`. This makes `cargo mutants` work properly
on trees where it previously failed to find the source.
- New `--version` option.
- New: Write a `lock.json` into the `mutants.out` directory including the start
timestamp, cargo-mutants version, hostname and username. Take a lock on this
file while `cargo mutants` is running, so that it doesn't crash or get
confused if two tasks try to write to the same directory at the same time.
- New: Restored a `--list-files` option.
- Changed: Error if no mutants are generated, which probably indicates a bug
or configuration error(?)
## 0.2.5
Released 2022-04-14
- New `--file` command line option to mutate only functions in source files
matching a glob.
- Improved: Don't attempt to mutate functions called `new` or implementations of
`Default`. cargo-mutants can not yet generate good mutations for these so they
are generally false positives.
- Improved: Better display of `<impl Foo for Bar>::foo` and similar type paths.
- New: `--output` directory to write `mutants.out` somewhere other than the
source directory.
## 0.2.4
Released 2022-03-26
- Fix: Ignore errors setting file mtimes during copies, which can cause failures on
Windows if some files are readonly.
- Fix: Log file names now include only the source file relative path, the line
number, and a counter, so they are shorter, and shouldn't cause problems on
filesystems with length limits.
- Change: version-control directories like `.git` are not copied with the source
tree: they should have no effect on the build, so copying them is just a
waste.
- Changed/improved json logs in `mutants.out`:
- Show durations as fractional seconds.
- Outcomes include a "summary" field.
## 0.2.3
Released 2022-03-23
- Switch from Indicatif to [Nutmeg](https://github.com/sourcefrog/nutmeg) to
draw progress bars and output. This fixes a bug where terminal output
line-wraps badly, and adds a projection for the total estimated time to
completion.
- Change: Mutants are now tested in random order by default, so that repeated
runs are more likely to surface interesting new findings early, rather
than repeating previous results. The previous behavior of testing mutants
in the deterministic order they're encountered in the tree can be restored
with `--no-shuffle`.
## 0.2.2
Released 2022-02-16
- The progress bar now shows which mutant is being tested out of how many total.
- The automatic timeout is now set to the minimum of 20 seconds, or 5x the time
of the tests in a baseline tree, to reduce the incidence of false timeouts on
machines with variable throughput.
- Ctrl-c (or `SIGINT`) interrupts the program during copying the tree.
Previously it was not handled until the copy was complete.
- New `--no-copy-target` option.
## 0.2.1
Released 2022-02-10
- Arguments to `cargo test` can be passed on the command line after `--`. This
allows, for example, skipping doctests or setting the number of test threads.
<https://github.com/sourcefrog/cargo-mutants/issues/15>
## 0.2.0
Released 2022-02-06
- A new `--timeout SECS` option to limit the runtime of any `cargo test`
invocation, so that mutations that cause tests to hang don't cause
`cargo mutants` to hang.
A default timeout is set based on the time to run tests in an unmutated tree.
There is no timeout by default on the unmutated tree.
On Unix, the `cargo` subprocesses run in a new process group. As a consequence
ctrl-c is explicitly caught and propagated to the child processes.
- Show a progress bar while looking for mutation opportunities, and show the
total number found.
- Show how many mutation opportunities were found, before testing begins.
- New `--shuffle` option tests mutants in random order.
- By default, the output now only lists mutants that were missed or that timed
out. Mutants that were caught, and mutants that did not build, can be printed
with `--caught` and `--unviable` respectively.
## 0.1.0
Released 2021-11-30
- Logs and other information are written into `mutants.out` in the source
directory, rather than `target/mutants`.
- New `--all-logs` option prints all Cargo output to stdout, which is verbose
but useful for example in CI, by making all the output directly available in
captured stdout.
- The output distinguishes check or build failures (probably due to an unviable
mutant) from test failures (probably due to lacking coverage.)
- A new file `mutants.out/mutants.json` lists all the generated mutants.
- Show function return types in some places, to make it easier to understand
whether the mutants were useful or viable.
- Run `cargo check --tests` and `cargo build --tests` in the source directory to
freshen the build and download any dependencies, before copying it to a
scratch directory.
- New `--check` option runs `cargo check` on generated mutants to see if they
are viable, without actually running the tests. This is useful in tuning
cargo-mutants to generate better mutants.
- New `--no-times` output hides times (and tree sizes) from stdout, mostly to
make the output deterministic and easier to match in tests.
- Mutate methods too!
## 0.0.4
Released 2021-11-10
- Fixed `cargo install cargo-mutants` (sometimes?) failing due to the `derive`
feature not getting set on the `serde` dependency.
- Show progress while copying the tree.
- Respect the `$CARGO` environment variable so that the same toolchain is used
to run tests as was used to invoke `cargo mutants`. Concretely,
`cargo +nightly mutants` should work correctly.
## 0.0.3
Released 2021-11-06
- Skip functions or modules marked `#[test]`, `#[cfg(test)]` or
`#[mutants::skip]`.
- Early steps towards type-guided mutations:
- Generate mutations of `true` and `false` for functions that return `bool`
- Empty and arbitrary strings for functions returning `String`.
- Return `Ok(Default::default())` for functions that return `Result<_, _>`.
- Rename `--list-mutants` to just `--list`.
- New `--list --json`.
- Colored output makes test names and mutations easier to read (for me at
least.)
- Return distinct exit codes for different situations including that uncaught
mutations were found.
## 0.0.2
- Functions that should not be mutated can be marked with `#[mutants::skip]`
from the [`mutants`](https://crates.io/crates/mutants) helper crate.
## 0.0.1
First release.