CARGO-FIX(1)

📦 version 1.83.0, in ubuntu jammy, ubuntu noble

CARGO-FIX 💅✨

okay bestie, welcome to the General Commands Manual page for cargo-fix, and honestly? it's a banger. strap in. 🎀

NAME 🦋

cargo-fix — Automatically fix lint warnings reported by rustc

SYNOPSIS ✨

cargo fix [options]

DESCRIPTION 💖

okay so this Cargo subcommand is literally the friend who takes rustc's suggestions — you know, the diagnostics, the warnings, all of it — and actually applies them to your source code. it exists to automate the stuff rustc was already telling you to fix. no cap. 🔥

when you run cargo fix, under the hood it's running cargo-check(1). any warnings that apply to your crate get fixed automatically (if it's possible, anyway), and every remaining warning gets shown to you once the check process is done. so like, if you want to apply all the fixes to the current package, you run:

cargo fix

which behaves exactly the same as cargo check --all-targets. periodt. 👑

lowkey important: cargo fix can only fix code that gets compiled normally by cargo check. so if some code is conditionally enabled with optional features, you've gotta enable those features for that code to even get analyzed:

cargo fix --features foo

same energy with other cfg expressions, like platform-specific code — you need to pass --target to fix code for that target:

cargo fix --target x86_64-pc-windows-gnu

if you hit any problems with cargo fix, or you just have questions or feature requests, please don't hesitate to file an issue at <https://github.com/rust-lang/cargo>. they want to hear from you fr fr 🫶

Edition migration 🌈

the cargo fix subcommand can also migrate a package from one edition <https://doc.rust-lang.org/edition-guide/editions/transitioning-an-existing-project-to-a-new-edition.html> to the next one. the general procedure is:

  1. Run cargo fix --edition. consider also using the --all-features flag if your project has multiple features. you may also want to run cargo fix --edition multiple times with different --target flags if your project has platform-specific code gated by cfg attributes.
  2. Modify Cargo.toml to set the edition field <https://doc.rust-lang.org/cargo/reference/manifest.html#the-edition-field> to the new edition.
  3. Run your project tests to verify that everything still works. if new warnings show up, you may want to consider running cargo fix again (without the --edition flag) to apply any suggestions the compiler gives you.

and hopefully that's it!! 🎉 just keep in mind the caveats mentioned above — that cargo fix can't update code for inactive features or cfg expressions. also, in some rare cases, the compiler is unable to automatically migrate all code to the new edition, and that may require manual changes after building with the new edition. 💀 (annoying, but survivable.)

✨ OPTIONS ✨

🛠 Fix options 💅

  • --broken-code — fix code even if it already has compiler errors. this is useful if cargo fix fails to apply the changes. it will apply the changes and leave the broken code sitting in the working directory for you to inspect and manually fix. 🙈
  • --edition — apply changes that will update the code to the next edition. heads up: this does not update the edition in the Cargo.toml manifest — you have to update that manually after cargo fix --edition has finished. ✨
  • --edition-idioms — apply suggestions that will update code to the preferred style for the current edition. iconic behavior.
  • --allow-no-vcs — fix code even if a VCS was not detected.
  • --allow-dirty — fix code even if the working directory has changes.
  • --allow-staged — fix code even if the working directory has staged changes.

📦 Package Selection 🎀

by default, when no package selection options are given, the packages selected depend on the selected manifest file (based on the current working directory if --manifest-path is not given). if the manifest is the root of a workspace, then the workspace's default members are selected; otherwise only the package defined by the manifest will be selected.

the default members of a workspace can be set explicitly with the workspace.default-members key in the root manifest. if this is not set, a virtual workspace will include all workspace members (equivalent to passing --workspace), and a non-virtual workspace will include only the root crate itself.

  • -p *spec*…, --package *spec*… — fix only the specified packages. see cargo-pkgid(1) for the SPEC format. this flag may be specified multiple times and supports common Unix glob patterns like *, ? and []. however, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each pattern. 🐚
  • --workspace — fix all members in the workspace.
  • --all — deprecated alias for --workspace. (old news bestie, it still works but like… use --workspace.)
  • --exclude *SPEC*… — exclude the specified packages. must be used in conjunction with the --workspace flag. this flag may be specified multiple times and supports common Unix glob patterns like *, ? and []. however, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each pattern.

🎯 Target Selection 🦋

when no target selection options are given, cargo fix will fix all targets (--all-targets implied). binaries are skipped if they have required-features that are missing.

passing target selection flags will fix only the specified targets.

note that --bin, --example, --test and --bench flags also support common Unix glob patterns like *, ? and []. however, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each glob pattern. 💖

  • --lib — fix the package's library.
  • --bin *name*… — fix the specified binary. this flag may be specified multiple times and supports common Unix glob patterns.
  • --bins — fix all binary targets.
  • --example *name*… — fix the specified example. this flag may be specified multiple times and supports common Unix glob patterns.
  • --examples — fix all example targets.
  • --test *name*… — fix the specified integration test. this flag may be specified multiple times and supports common Unix glob patterns.
  • --tests — fix all targets in test mode that have the test = true manifest flag set. by default this includes the library and binaries built as unittests, and integration tests. be aware that this will also build any required dependencies, so the lib target may be built twice (once as a unittest, and once as a dependency for binaries, integration tests, etc.). targets may be enabled or disabled by setting the test flag in the manifest settings for the target. 😭
  • --bench *name*… — fix the specified benchmark. this flag may be specified multiple times and supports common Unix glob patterns.
  • --benches — fix all targets in benchmark mode that have the bench = true manifest flag set. by default this includes the library and binaries built as benchmarks, and bench targets. be aware that this will also build any required dependencies, so the lib target may be built twice (once as a benchmark, and once as a dependency for binaries, benchmarks, etc.). targets may be enabled or disabled by setting the bench flag in the manifest settings for the target.
  • --all-targets — fix all targets. this is equivalent to specifying --lib --bins --tests --benches --examples.

🌸 Feature Selection 🌈

the feature flags let you control which features are enabled. when no feature options are given, the default feature is activated for every selected package.

see the features documentation <https://doc.rust-lang.org/cargo/reference/features.html#command-line-feature-options> for more details.

  • -F features, --features features — space or comma separated list of features to activate. features of workspace members may be enabled with package-name/feature-name syntax. this flag may be specified multiple times, which enables all specified features.
  • --all-features — activate all available features of all selected packages.
  • --no-default-features — do not activate the default feature of the selected packages.

🔥 Compilation Options ⭐

  • --target triple — fix for the given architecture. the default is the host architecture. the general format of the triple is <arch><sub>-<vendor>-<sys>-<abi>. run rustc --print target-list for a list of supported targets. this flag may be specified multiple times.

this may also be specified with the build.target config value <https://doc.rust-lang.org/cargo/reference/config.html>.

note that specifying this flag makes Cargo run in a different mode where the target artifacts are placed in a separate directory. see the build cache <https://doc.rust-lang.org/cargo/reference/build-cache.html> documentation for more details. 🗂️

  • -r, --release — fix optimized artifacts with the release profile. see also the --profile option for choosing a specific profile by name.
  • --profile name — fix with the given profile.

as a special case, specifying the test profile will also enable checking in test mode, which will enable checking tests and enable the test cfg option. see rustc tests <https://doc.rust-lang.org/rustc/tests/index.html> for more detail.

see the reference <https://doc.rust-lang.org/cargo/reference/profiles.html> for more details on profiles.

  • --timings=fmts — output information about how long each compilation takes, and track concurrency information over time. accepts an optional comma-separated list of output formats; --timings without an argument will default to --timings=html. specifying an output format (rather than the default) is unstable and requires -Zunstable-options. valid output formats:
    • html (unstable, requires -Zunstable-options): write a human-readable file cargo-timing.html to the target/cargo-timings directory with a report of the compilation. also write a report to the same directory with a timestamp in the filename if you want to look at older runs. HTML output is suitable for human consumption only, and does not provide machine-readable timing data.
    • json (unstable, requires -Zunstable-options): emit machine-readable JSON information about timing information.

💜 Output Options 🫶

  • --target-dir directory — directory for all generated artifacts and intermediate files. may also be specified with the CARGO_TARGET_DIR environment variable, or the build.target-dir config value <https://doc.rust-lang.org/cargo/reference/config.html>. defaults to target in the root of the workspace.

✨ Display Options ✨

  • -v, --verbose — bestie wants the verbose output okay 💬 use it twice for "very verbose" mode, which spills the extra tea like dependency warnings and build script output. You can also set this with the term.verbose config value (https://doc.rust-lang.org/cargo/reference/config.html).
  • -q, --quiet — shhh 🤫 no cargo log messages. Also settable via the term.quiet config value (https://doc.rust-lang.org/cargo/reference/config.html).
  • --color when — controls when colored output shows up. Valid values, no cap:
    • auto (default): it auto-detects whether your terminal can do color, lowkey smart 💅
    • always: colors. always. periodt 🌈
    • never: no colors, ever, muted mode 🎀

Also settable with the term.color config value (https://doc.rust-lang.org/cargo/reference/config.html).

  • --message-format fmt — the output format for diagnostic messages. Can be given multiple times and it's a bunch of comma-separated values. Valid values:
    • human (default): displays in a human-readable text format. Conflicts with short and json.
    • short: emits shorter, human-readable text messages. Conflicts with human and json.
    • json: emits JSON messages to stdout. Peep the reference (https://doc.rust-lang.org/cargo/reference/external-tools.html#json-messages) for more deets. Conflicts with human and short.
    • json-diagnostic-short: makes sure the rendered field of JSON messages contains the "short" rendering from rustc. Cannot be used with human or short.
    • json-diagnostic-rendered-ansi: makes sure the rendered field of JSON messages contains embedded ANSI color codes so it respects rustc's default color scheme. Cannot be used with human or short.
    • json-render-diagnostics: tells Cargo to not include rustc diagnostics in the JSON messages it prints, and instead have Cargo itself render the JSON diagnostics coming from rustc. Cargo's own JSON diagnostics and others coming from rustc are still emitted. Cannot be used with human or short.

🌸 Manifest Options 🌸

  • --manifest-path path — the path to the Cargo.toml file. By default Cargo goes looking for Cargo.toml in the current directory or any parent directory 🕵️♀️
  • --ignore-rust-version — ignores the rust-version specification in packages. yeah we're pretending that's not there 🙈
  • --locked — asserts that the exact same dependencies and versions are used as when the existing Cargo.lock file was originally generated. Cargo will exit with an error when either of these scenarios comes up:
    • The lock file is missing. 😭
    • Cargo attempted to change the lock file because of a different dependency resolution.

It may be used in environments where you want deterministic builds, like in CI pipelines. consistency queen 👑

  • --offline — prevents Cargo from accessing the network for any reason. Without this flag, Cargo stops with an error if it needs the network and the network isn't available. With this flag, Cargo will attempt to proceed without the network if it can.
Beware bestie — this may result in different dependency resolution than online mode. Cargo will restrict itself to crates that are downloaded locally, even if there might be a newer version as indicated in the local copy of the index. Check out the cargo-fetch(1) command to download dependencies before going offline 💾

Also settable with the net.offline config value (https://doc.rust-lang.org/cargo/reference/config.html).

  • --frozen — equivalent to specifying both --locked and --offline at the same time. two-for-one, iconic 🫶
  • --lockfile-path PATH — changes the path of the lockfile from the default (<workspace_root>/Cargo.lock) to PATH. PATH must end with Cargo.lock (e.g. --lockfile-path /tmp/temporary-lockfile/Cargo.lock). Note that providing --lockfile-path will ignore the existing lockfile at the default path, and instead will either use the lockfile from PATH, or write a new lockfile into the provided PATH if it doesn't exist. This flag can be used to run most commands in read-only directories, writing the lockfile into the provided PATH.
This option is only available on the nightly channel (https://doc.rust-lang.org/book/appendix-07-nightly-rust.html) and requires the -Z unstable-options flag to enable (see #14421, https://github.com/rust-lang/cargo/issues/14421). nightlies only, you've been warned 💀

💜 Common Options 💜

  • +toolchain — if Cargo was installed with rustup, and the first argument to cargo begins with +, it gets interpreted as a rustup toolchain name (like +stable or +nightly). See the rustup documentation (https://rust-lang.github.io/rustup/overrides.html) for more info on how toolchain overrides work.
  • --config KEY=VALUE or PATH — overrides a Cargo configuration value. The argument should be in TOML syntax of KEY=VALUE, or given as a path to an extra configuration file. This flag may be specified multiple times. See the command-line overrides section (https://doc.rust-lang.org/cargo/reference/config.html#command-line-overrides) for more info.
  • -C PATH — changes the current working directory before executing any specified operations. This affects stuff like where cargo looks by default for the project manifest (Cargo.toml), and also the directories searched for discovering .cargo/config.toml, for example. This option must appear before the command name, like:
cargo -C path/to/my-project build
This option is only available on the nightly channel (https://doc.rust-lang.org/book/appendix-07-nightly-rust.html) and requires the -Z unstable-options flag to enable (see #10098, https://github.com/rust-lang/cargo/issues/10098). ✨
  • -h, --help — prints help information 🫶
  • -Z flag — unstable (nightly-only) flags for Cargo. Run cargo -Z help for the details.

🦋 Miscellaneous Options 🦋

  • -j N, --jobs N — number of parallel jobs to run. Also settable with the build.jobs config value (https://doc.rust-lang.org/cargo/reference/config.html). Defaults to the number of logical CPUs. If negative, it sets the max number of parallel jobs to the number of logical CPUs plus the provided value. If a string default is provided, it sets the value back to defaults. Should not be 0 — do not do that 🚫
  • --keep-going — builds as many crates in the dependency graph as possible, rather than aborting the build on the first one that fails to build.

For example, if the current package depends on dependencies fails and works, one of which fails to build, cargo fix -j1 may or may not build the one that succeeds (depending on which one of the two builds Cargo picked to run first), whereas cargo fix -j1 --keep-going would definitely run both builds, even if the one run first fails. resilience slay 💪

🌈 ENVIRONMENT 🌈

See the reference (https://doc.rust-lang.org/cargo/reference/environment-variables.html) for the deets on environment variables that Cargo reads. iykyk 📖

⭐ EXIT STATUS ⭐

  • 0: Cargo succeeded. 🎉
  • 101: Cargo failed to complete. 😭

🎀 EXAMPLES 🎀

  1. Apply compiler suggestions to the local package:
cargo fix
  1. Update a package to prepare it for the next edition:
cargo fix --edition
  1. Apply suggested idioms for the current edition:
cargo fix --edition-idioms

👑 SEE ALSO 👑

cargo(1), cargo-check(1)

and that's the whole page bestie, you ate 💅✨ This lil gem lives in the Cargo manual as CARGO-FIX(1), and yeah the footer carries the source/version + date stamp — consider it your timestamped receipt that you read the entire thing. go forth and cargo fix responsibly 🫶🌸

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