Github actions suddenly throwing "no version specified" for reusable workflows that worked yesterday - github

Question

I'm not sure if this is a bug or a breaking change happened as of yesterday, I have a pretty simple setup calling three reusable workflows:
name: pr-checks
on:
pull_request:
branches: "**"
jobs:
lint:
name: Call Lint
uses: ./.github/checks/check-lint.yaml
test:
name: Call Test
uses: ./.github/checks/check-test.yaml
e2e:
name: Call E2E
uses: ./.github/checks/check-e2e.yaml
But this throws
"invalid value workflow reference: no version specified"
as of now, even though identical workflows have worked yesterday.
When reusing workflows like this at the 'job' level - it is not necessary to specify version, in fact, it used to error out if I specified the version.
Screenshots attached as I think this doesn't make much sense.
I did click on 're-run all jobs and it re-ran successfully.
However, without any discenrable difference and after also removing the build step just to be sure there's nothing weird happening there:

Answer 1

As you can see in your 2 screenshots, one is referring to the .github/workflows directory (the one which worked), and the other to the .github/checks directory (the one which didn't).
Short answer: If you change the workflow folder back to workflows instead of checks, it should work as expected.
Long answer: It seems there is a confusion between the syntax of two different concepts:
local actions (using an action in the same repo)
reusable workflows (reusing the same workflow in different workflows)
LOCAL ACTIONS
To access local actions (folders with action.yml file) from your workflow, you need to use the actions/checkout first, to allow it to access the other repository folders and files.
Example:
steps:
- uses: actions/checkout#v3 # Necessary to access local action
- name: Local Action Call
uses: ./.github/actions/local-action #path/to/action
I've made a POC here some time ago if you want to have a look.
REUSABLE WORKFLOWS
Now, if you want to use reusable workflows, the issue is different:
As with other workflow files, you locate reusable workflows in the
.github/workflows directory of a repository. Subdirectories of the
workflows directory are not supported.
GitHub documentation reference
In that case, according to this other section from the documentation:
You reference reusable workflow files using one of the following
syntaxes:
{owner}/{repo}/.github/workflows/{filename}#{ref} for reusable
workflows in public repositories.
./.github/workflows/{filename} for reusable workflows in the same repository.
{ref} can be a SHA, a release tag, or a branch name.
Example:
lint:
name: Call Lint
uses: ./.github/workflows/check-lint.yaml#{SHA/TAG/BRANCH}
or
lint:
name: Call Lint
uses: ./.github/workflows/check-lint.yaml
Here is another POC for the workflow call using this reusable workflow
CONCLUSION
It's like you were trying to call a reusable workflow as if it was a local action, which won't work as reusable workflows need to be located in the .github/workflows directory.
Note that you could eventually add the #branch-name at the end of the workflow call to be sure to use the workflow from the branch you want to test if the reusable workflow is already present on the default branch.