search

facebookincubator / buck2-change-detector

Given a Buck2 built project and a set of changes (e.g. from source control) compute the targets that may have changed. Sometimes known as a target determinator, useful for optimizing a CI system.
Apache License 2.0
28 stars 4 forks source link

`btd` outputs text rather than (no) targets when no targets are impacted #2

Closed cbarrete closed 4 months ago

cbarrete commented 4 months ago

When a change causes no targets to require a rebuild, the output of btd is not a valid list of targets:

> supertd btd --cells cells.json --changes changes.txt --base base.jsonl --diff diff.jsonl
2024-02-27T21:53:31.074644Z  INFO Starting reading cells at 0.000s
2024-02-27T21:53:31.074679Z  INFO Starting reading changes at 0.000s
2024-02-27T21:53:31.074692Z  INFO Starting reading base at 0.000s
2024-02-27T21:53:31.094598Z  INFO Starting validating universe at 0.020s
2024-02-27T21:53:31.094620Z  INFO Starting reading diff at 0.020s
2024-02-27T21:53:31.101620Z  INFO Starting immediate changes at 0.027s
2024-02-27T21:53:31.103091Z  INFO Starting error validation at 0.028s
2024-02-27T21:53:31.103140Z  INFO Starting recursive changes at 0.028s
2024-02-27T21:53:31.103149Z  INFO Starting printing changes at 0.029s
Level 0
2024-02-27T21:53:31.103162Z  INFO Starting finish with 0 immediate changes, 0 total changes at 0.029s

where Level 0 is written to stdout and the rest to stderr. This is a (minor) inconvenience because we cannot directly pass that output to buck2 build/buck2 test as suggested in the README. Is this expected behavior? If so, can we expect that output to be stable (because right now I explicitly check against Level 0 to check if targets need to be run or not, which seems fragile)?

cbarrete commented 4 months ago

I misdiagnosed this one, Level X is always in the output, so the correct approach is to use one of the JSON output flags and parse that instead.

It would be nice to have a way to dump just the targets to stdout, but it's workable for now.

ndmitchell commented 4 months ago

Yep, I would encourage anyone who wants to consume the output to use the JSON - sooner or later the distance tends to come into play and I don't want people parsing that from stdout. But I'm not averse to a --quiet option which just prints the targets that have changed and no levels or anything.