"tools": Composer cache not working when using specific Composer version

[tyrann0us]

Describe the bug
When using the tools input to specify a specific Composer version (e.g. tools: composer:v1), Composer won't use cache as described here and here.

Version

• I have checked releases, and the bug exists in the latest patch version of v1 or v2.
• v2
• v1

Runners

• GitHub Hosted
• Self Hosted

Operating systems
ubuntu-latest (resolves to ubuntu-18.04, still)

PHP versions
7.4

To Reproduce

name: Deploy
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - id: composer-cache
        run: |
          echo "::set-output name=dir::$(composer config cache-files-dir)"
      - uses: shivammathur/setup-php@v2
        with:
          tools: composer:v1
      - uses: actions/cache@v1
        with:
          path: ${{ steps.composer-cache.outputs.dir }}
          key: ${{ runner.os }}-composer-
      - run: composer validate --ansi
      - run: composer install -vv --ansi --no-dev --prefer-dist

Note that unrelated parts of the workflow files have been removed.

Expected behavior
Composer to load packages from cache on subsequent runs.

Screenshots/Logs

Note that the screenshot only shows the very first packages, the rest is redacted.

Additional context
We need to use the tools input to force Composer v1 because GitHub Actions started to use Composer v2 by default, see actions/runner-images#1924 and actions/runner-images@215647d.

Note that we haven't checked whether this issue also occurs with Composer v2.

Cache used to worked before.

What other information do you need from me to investigate?

[shivammathur]

@tyrann0us Can you move the step to get the composer's cache directory after setup-php step and see if the problem is still there.

-      - id: composer-cache
-        run: |
-          echo "::set-output name=dir::$(composer config cache-files-dir)"
       - uses: shivammathur/setup-php@v2
         with:
           tools: composer:v1
+      - id: composer-cache
+        run: |
+        echo "::set-output name=dir::$(composer config cache-files-dir)"

[tyrann0us]

@shivammathur, thanks for your fast response. That did the trick indeed. I should have noticed this myself; sorry for wasting your time.

[shivammathur]

Its Alright 👍