Configuration

QuickRust never reads Cargo’s configuration (.cargo/config.toml) for its own settings, and Cargo never reads QuickRust’s. qrust policy explain prints every key with its effective value, environment variable and origin; --format json prints the same as JSON.

Sources and precedence

Later sources override earlier ones, key by key:

An empty environment variable counts as unset. A configuration file that does not exist counts as empty.

File format

TOML. output and mode are top-level keys; every other key is name inside the table named by its first part:

mode = "fast"

[cache]
provider = "sccache"
max-size = "40GiB"

[measurement]
report = ".qrust/runs/{session}.json"

Validation

Invalid configuration stops every command except qrust upstream, with exit status 2 and a message that names the key and its source:

• a key that does not exist (unknown configuration key cache.providr in <file>);
• a value outside the key’s type or allowed values (invalid value "maybe" for cache.fail from <file>: expected one of open, closed);
• a value of the wrong TOML type;
• invalid TOML;
• any environment variable whose name starts with QRUST_ and is not a key’s variable or one of QuickRust’s internal variables (Environment): unknown configuration variable QRUST_…``.

Value types

Keys

A key’s environment variable is QRUST_ followed by the key in upper case with . and - replaced by _, except for the keys whose variable is listed otherwise above (QRUST_MODE, QRUST_OUTPUT, QRUST_NESTED, QRUST_REPORT, QRUST_EARLY_CUTOFF, QRUST_CACHE_MAX_SIZE, QRUST_CACHE_MIN_FREE, QRUST_UPDATE_URL, QRUST_TOOLCHAIN_AUTO_UPDATE, QRUST_DIST_SERVER).

A run counts as CI when one of CI, GITHUB_ACTIONS, GITLAB_CI, BUILDKITE, JENKINS_URL, TF_BUILD, TEAMCITY_VERSION is set to a value other than empty, false or 0. CI selects incremental.ci over incremental.local-dev and turns off toolchain.auto-update. An explicit CARGO_INCREMENTAL in the environment always wins over both incremental.* keys.

Toolchain selection

The toolchain of a command is the first of:

qrust toolchain list and qrust doctor show the selected toolchain and what selected it. rustup’s per-directory overrides have no equivalent.

Toolchain names

Anything else is an error before any download. An undated nightly resolves to the newest nightly of the last seven days that has every component and target asked for.

Toolchain files

rust-toolchain.toml, or rust-toolchain (the same TOML, or a single line naming the toolchain). A directory holding both is an error.

[toolchain]
channel = "1.98"                       # or path = "../my-toolchain", never both
components = ["rust-src", "llvm-tools"]
targets = ["wasm32-unknown-unknown"]
profile = "minimal"                    # minimal | default | complete

Any other key or table is an error. The toolchain, its components and targets, and the standard library of every --target a command builds for are installed on first use.

Toolchain profiles

A toolchain installed without a profile gets default.

Files QuickRust reads in a repository