GitHub Actions: Cache Maven .m2 repository on Windows environment C\:\\Users\runneradmin\\.m2\repository: Cannot stat: No such file or directory

Question

As the docs state in order to cache the Maven dependencies with GitHub Actions all we have to use is the actions/cache action like this:

steps:
  - uses: actions/checkout@v2
  - name: Set up JDK 1.8
    uses: actions/setup-java@v1
    with:
      java-version: 1.8
  - name: Cache Maven packages
    uses: actions/cache@v2
    with:
      path: ~/.m2
      key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
      restore-keys: ${{ runner.os }}-m2
  - name: Build with Maven
    run: mvn --batch-mode --update-snapshots verify

However using the windows-2016 GitHub Actions environment, this doesn't provides us with a working cache - as the logs states:

Post job cleanup.
"C:\Program Files\Git\usr\bin\tar.exe" --posix --use-compress-program "zstd -T0" -cf cache.tzst -P -C D:/a/spring-boot-admin/spring-boot-admin --files-from manifest.txt --force-local
/usr/bin/tar: C\:\\Users\runneradmin\\.m2\repository: Cannot stat: No such file or directory
/usr/bin/tar: Exiting with failure status due to previous errors
Warning: Tar failed with error: The process 'C:\Program Files\Git\usr\bin\tar.exe' failed with exit code 2

How to fix this?

Answer 1

It seems that the path to the Maven repository isn't correctly initialized. As this issue describes the paths are written with \\ instead of / which GNU tar expects. The fix was already provided in Dec 2020, so it made it to the version v2.1.4. The last version v2.1.3 was released in November. But sadly there is a bug in pointing the v2 to the latest v2.1.4 (as normally expected by GitHub Actions users). Therefore to solve this issue, we need to explicitely specifiy the full actions/cache version v2.1.4 like this:

steps:
  - uses: actions/checkout@v2
  - name: Set up JDK 1.8
    uses: actions/setup-java@v1
    with:
      java-version: 1.8
  - name: Cache Maven packages
    uses: actions/[email protected]
    with:
      path: ~/.m2
      key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
      restore-keys: ${{ runner.os }}-m2
  - name: Build with Maven
    run: mvn --batch-mode --update-snapshots verify

Now it should work like a charm (see logs here).