I would like to be able to validate the workflows (for syntax errors) in CI/CD.
Would act allow this?

You can use dry run mode of act or use https://github.com/rhysd/actionlint

I think --list is better, than dryrun due to open bugs and concerning test coverage in act.

If you mean the basic schema validation I added last year.

Thanks for your input!

I've tried act --list but the command lists the workflows, without doing any validation on them (or so it seems).
I broke the yaml format, I put wrong values for events.. but act is still happy with it :)
act --dryrun also ignores any issues with event names, and other things, it doesn't seem to be doing much validation either - it happily runs with broken schema :)

I need a tool that will validate the github workflows for syntax/schema, so we can catch any issues at pull request time.
Do you know if any official tool from Github, for this purpose? I've spent quite a bit of time searching, but I couldn't find one..

I did try actionlint, but it has some issues (false positives), so I can't really use it as it is now.. Their repository has over 100 issues opened, but I'm not sure how much activity on it ..
I also tried github-workflow-validator, but this one has a long standing issue with glob validation, so that's also a deal breaker :(

I broke the yaml format, I put wrong values for events.. but act is still happy with it :)

To comply with the GitHub Action spec we cannot use the strict schema

• Our source of the schema (The official GitHub Actions Extension) has errors and would reject valid workflows in strict mode re fix: use non strict schema to allow some undefined behavior #2524

If the previous v0.2.74 would report your change as error before execution, then I could create an --validate --strict flag that might do just what you want using the disabled strict validation

Yes, that command will probably do the trick, if implemented.
Thanks for the great feedback!