Monorepos

Affected detection

In a large repo you don’t want to run everything on every change. yatr affected <git-ref> lists the tasks touched by changes since a ref — a task is affected when one of its sources/watch globs matches a changed file, and the result propagates to everything that (transitively) depends on it.

yatr affected main                     # what would I need to run for this branch?
yatr affected HEAD~1 --format json     # machine-readable, for CI
yatr run --affected origin/main test lint build   # run only the affected ones

Caching gives you correctness (unchanged tasks are cache hits); affected detection adds speed at scale by not even considering tasks git says can’t have moved. A task that declares no sources is treated as always affected — declaring sources is what unlocks skipping.

Splitting config across files

Keep task definitions next to the code they build and compose them from a root yatr.toml with include:

# yatr.toml
include = ["frontend/yatr.toml", "backend/yatr.toml"]

[tasks.build-all]
depends = ["fe-build", "be-build"]   # tasks defined in the included files

Includes are resolved relative to the including file and merged recursively (cycles are detected). Tasks and env are composed; the root file’s settings are authoritative. A task defined in two files is an error — names are global.