Check Outputted List is Empty? #27085

merlinstardust · 2021-06-14T14:06:20Z

merlinstardust
Jun 14, 2021

Anyone know how I can check if an outputted list is empty in GitHub Actions?

I’m using dorny/paths-filter, specifically the use change detection to configure matrix job example under conditional execution .

I was thinking of something like if: join(steps.filter.outputs.packages) and compare the joined result to an empty list, but I’m not sure if that would work or if there is a better way with some kind of hidden .length value

Answered by Simran-B

Jun 14, 2021

GitHub Actions expressions are fairly limited and I haven’t seen a length function to this day.

However, in this case you can simply compare the output, which is a JSON string, to the JSON string for an empty array:

...
  build:
    needs: changes
    if: needs.changes.outputs.packages != '[]'
...

View full answer

Simran-B · 2021-06-14T16:37:10Z

Simran-B
Jun 14, 2021

GitHub Actions expressions are fairly limited and I haven’t seen a length function to this day.

However, in this case you can simply compare the output, which is a JSON string, to the JSON string for an empty array:

...
  build:
    needs: changes
    if: needs.changes.outputs.packages != '[]'
...

0 replies

dmitry-stepanenko · 2022-09-02T06:08:30Z

dmitry-stepanenko
Sep 2, 2022

Might work slightly better to check the availability of the first element in the parsed array instead of a string

...
  build:
    needs: changes
    if: fromJson(needs.changes.outputs.packages)[0] != null
...

2 replies

Simran-B Sep 2, 2022

[null] is technically a non-empty array but wouldn't satisfy the condition. You probably get away with it most of the time, however.

dmitry-stepanenko Sep 2, 2022

Yea, my use cases are not that generic, works great for an array of integers for example

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GitHub Community

Check Outputted List is Empty? #27085

merlinstardust Jun 14, 2021

Replies: 2 comments · 2 replies

Simran-B Jun 14, 2021

dmitry-stepanenko Sep 2, 2022

Simran-B Sep 2, 2022

dmitry-stepanenko Sep 2, 2022

merlinstardust
Jun 14, 2021

Replies: 2 comments 2 replies

Simran-B
Jun 14, 2021

dmitry-stepanenko
Sep 2, 2022