[bug] Regression in 4.2.0 -- download-path is no longer populated if no artifacts are found with pattern match #390

What happened?

Using the v4 tag broke automation that relies on the download-path output always being populated. I've determined this to be a regression in v4.2.0 release that was just put out -- where if an inputs.pattern matches no artifacts, the output is left empty instead of being populated.

This is a behavioral regression from a minor tag bump

What did you expect to happen?

I expect an output to still exist.

More formally, I expect no behavioral regressions when relying on a minor version update -- as per semantic versioning.

How can we reproduce it?

Run a workflow that uses a pattern and matches on no artifacts. The output in v4.2.0 is empty, but in v4.1.* and before is non-empty.

Complete example:

name: Demo regression
on:
  pull_request:

jobs:
  check-v4-2-0:
    name: Check actions/download-artifact@v4.2.0
    runs-on: ubuntu-latest
    steps:
      - name: Download Action
        id: download
        uses: actions/download-artifact@v4.2.0
        with:
          pattern: this-artifact-doesnt-exist

      - name: Print Output
        run: |
          echo "v4.2.0 = ${{ steps.download.outputs.download-path }}" >> "${GITHUB_STEP_SUMMARY}"

  check-v4-1-9:
    name: Check actions/download-artifact@v4.1.9
    runs-on: ubuntu-latest
    steps:
      - name: Download Action
        id: download
        uses: actions/download-artifact@v4.1.9
        with:
          pattern: this-artifact-doesnt-exist

      - name: Print Output
        run: |
          echo "v4.1.9 = ${{ steps.download.outputs.download-path }}" >> "${GITHUB_STEP_SUMMARY}"

This produces in the STEP_SUMMARY:

v4.2.0 =

and

v4.1.9 = /home/runner/work/test-repo/test-repo

Anything else we need to know?

Nothing more to say on the ticket, though I'm interested in whether this was a deliberate change, and whether the output-path was not meant to be reliable when no artifacts are discovered? Was I relying on an implicit behavior I shouldn't have been?

What version of the action are you using?

v4.2.0

What are your runner environments?

linux

Are you on GitHub Enterprise Server? If so, what version?

No response