False Positive for Object Element Dereference

[Kurt-von-Laven]

Actionlint knows about array element dereferences, but not object element dereferences. For example, GitHub Actions supports the syntax ${{ join(needs.*.result, ' ') }} as documented in slack-templates' README despite the fact that needs is not an array. Actionlint 1.6.6 yields an error message of the following form:

[...]/.github/workflows/test.yaml:[row]:[col]: receiver of array element dereference must be type of array but got "{<job_id_1>: {outputs: {}; result: string}; <job_id_2>: {outputs: {}; result: string}}" [expression]
         |
[row] |           results: ${{ join(needs.*.result, ' ') }}

Thank you for creating Actionlint! It's quite nice to have a super easy way to check whether an action has syntax errors without wasting build credits.

[alambike]

We are seeing the same thing here with this expression:

      - name: Check failures
        if: ${{ contains(steps.*.outcome, 'failure') }}

.github/workflows/test.yml:128:26: receiver of array element dereference must be type of array but got "{pre: {outcome: string; outputs: {string => string}; conclusion: string}; pro: {outputs: {string => string}; conclusion: string; outcome: string}; metadata: {outputs: {string => string}; conclusion: string; outcome: string}; des: {conclusion: string; outcome: string; outputs: {string => string}}}" [expression]
    |
128 |         if: ${{ contains(steps.*.outcome, 'failure') }}
    |                          ^~~~~~~~~~~~~~~~

[rhysd]

Thank you for reporting this. It looks a bug of actionlint.

[rhysd]

https://docs.github.com/en/actions/learn-github-actions/expressions#object-filters

The document only mentions arrays as target of object filtering. So I thought the syntax was only for arrays when I implemented the type check. I think it was incorrect.

[Kurt-von-Laven]

Indeed; I noticed this as well when trying to find a link that would prove the syntax was supported and was pleasantly surprised that it was when I first tried it. I filed the issue linked above with GitHub to enhance their documentation accordingly.

[rhysd]

I tried

- run: |
    echo '${{ toJSON(fromJSON(env.JSON).*.foo) }}'
  env:
    JSON: '{"a": {"foo": "from a"}, "b": {"foo": "from b"}}'

and confirmed output

[
  "from a",
  "from b"
]

https://github.com/rhysd/actionlint/runs/4136626284?check_suite_focus=true

[rhysd]

With cabbf84, x.* is deduced to array<any> even if x is an object. This can prevent the false positive reported in this issue.

[rhysd]

The fix was released as v1.6.7

[Kurt-von-Laven]

I can confirm that this fix is working for us. Thank you!