QuickRust documentation

How to review and apply QuickRust’s recommendations

This guide shows you how to see what QuickRust recommends for a build, preview the change each recommendation implies, and apply or undo it.

In this section

QuickRust never changes your repository on its own. It only writes a file when you apply one specific, previewed change by its id, and only changes to QuickRust’s own configuration can be applied that way.

See the recommendations

qrust analyze recommendations
qrust analyze recommendations --run latest~1
qrust analyze recommendations --format json

Each recommendation has an id, the evidence it rests on, its expected impact, risk and confidence, and how to verify it. When the evidence supports nothing, QuickRust says so:

Recommendations
  None: the recorded evidence supports no recommendation.

Preview the changes

qrust fix --dry-run                    # every recommendation of the latest run
qrust fix --dry-run <REC_ID>           # one recommendation
qrust fix --dry-run <REC_ID> --option keep-incremental   # one of its alternatives
qrust fix --dry-run --run latest~1

For each recommendation the preview shows its class and state and, where a file change goes with it, the remediation id, the file and a unified diff. Nothing is written. A recommendation without a file change gets guidance instead (for example, which cargo::rerun-if-changed lines a build script needs).

The class decides what you can do with it:

  • safe: a change to QuickRust’s own configuration (.qrust/config.toml). It can be applied with qrust fix --apply.
  • review_required: a change to how the project is built (Cargo.toml profiles, dependencies, build scripts). QuickRust only shows it.

Apply a safe change

qrust fix --apply rem-1a2b3c4d5e6f

OK   Applied rem-1a2b3c4d5e6f to .qrust/config.toml; undo with: qrust fix --rollback rem-1a2b3c4d5e6f

QuickRust applies exactly what the preview showed. If the file changed since the preview, it refuses; run qrust fix --dry-run again. If the result is not a valid QuickRust configuration, it restores the file and says why.

Apply a change that needs review

Print only the diffs, read them, and apply them yourself:

qrust fix --dry-run <REC_ID> --patch > change.patch
git apply change.patch

Then verify the change the way the recommendation’s verify: line says, for example with an experiment (see How to measure the effect of a build setting), before you commit it.

Undo an applied change

qrust fix --rollback rem-1a2b3c4d5e6f

This restores the file as it was before (or removes it, if applying created it). If you edited the file after applying, QuickRust refuses to overwrite your edit; undo the change by hand.

If you meant Cargo’s fix

qrust fix is QuickRust’s command. For Cargo’s cargo fix (applying compiler suggestions), run cargo fix, or qrust upstream fix when cargo is not QuickRust.