download-artifact/docs/MIGRATION.md

Migration

• Migration
  • Multiple uploads to the same named Artifact
  • Overwriting an Artifact
  • Merging multiple artifacts

Several behavioral differences exist between Artifact actions v3 and below vs v4. This document outlines common scenarios in v3, and how they would be handled in v4.

Multiple uploads to the same named Artifact

In v3, Artifacts are mutable so it's possible to write workflow scenarios where multiple jobs upload to the same Artifact like so:

jobs:
  upload:
    strategy:
      matrix:
        runs-on: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.runs-on }}
    steps:
      - name: Create a File
        run: echo "hello from ${{ matrix.runs-on }}" > file-${{ matrix.runs-on }}.txt
      - name: Upload Artifact
        uses: actions/upload-artifact@v3
        with:
          name: my-artifact # NOTE: same artifact name
          path: file-${{ matrix.runs-on }}.txt
  download:
    needs: upload
    runs-on: ubuntu-latest
    steps:
      - name: Download All Artifacts
        uses: actions/download-artifact@v3
        with:
          name: my-artifact
          path: my-artifact
      - run: ls -R my-artifact

This results in a directory like so:

my-artifact/
  file-macos-latest.txt
  file-ubuntu-latest.txt
  file-windows-latest.txt

In v4, Artifacts are immutable (unless deleted). So you must change each of the uploaded Artifacts to have a different name and filter the downloads by name to achieve the same effect:

jobs:
  upload:
    strategy:
      matrix:
        runs-on: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.runs-on }}
    steps:
    - name: Create a File
      run: echo "hello from ${{ matrix.runs-on }}" > file-${{ matrix.runs-on }}.txt
    - name: Upload Artifact
-     uses: actions/upload-artifact@v3
+     uses: actions/upload-artifact@v4
      with:
-       name: my-artifact
+       name: my-artifact-${{ matrix.runs-on }}
        path: file-${{ matrix.runs-on }}.txt
  download:
    needs: upload
    runs-on: ubuntu-latest
    steps:
    - name: Download All Artifacts
-     uses: actions/download-artifact@v3
+     uses: actions/download-artifact@v4
      with:
-       name: my-artifact
        path: my-artifact
+       pattern: my-artifact-*
+       merge-multiple: true
    - run: ls -R my-artifact

In v4, the new pattern: input will filter the downloaded Artifacts to match the name specified. The new merge-multiple: input will support downloading multiple Artifacts to the same directory. If the files within the Artifacts have the same name, the last writer wins.

Overwriting an Artifact

In v3, the contents of an Artifact were mutable so something like the following was possible:

jobs:
  upload:
    runs-on: ubuntu-latest
    steps:
      - name: Create a file
        run: echo "hello world" > my-file.txt
      - name: Upload Artifact
        uses: actions/upload-artifact@v3
        with:
          name: my-artifact # NOTE: same artifact name
          path: my-file.txt
  upload-again:
    needs: upload
    runs-on: ubuntu-latest
    steps:
      - name: Create a different file
        run: echo "goodbye world" > my-file.txt
      - name: Upload Artifact
        uses: actions/upload-artifact@v3
        with:
          name: my-artifact # NOTE: same artifact name
          path: my-file.txt

The resulting my-file.txt in my-artifact will have "goodbye world" as the content.

In v4, Artifacts are immutable unless deleted. To achieve this same behavior, you can use overwrite: true to delete the Artifact before a new one is created:

jobs:
  upload:
    runs-on: ubuntu-latest
    steps:
      - name: Create a file
        run: echo "hello world" > my-file.txt
      - name: Upload Artifact
-       uses: actions/upload-artifact@v3
+       uses: actions/upload-artifact@v4
        with:
          name: my-artifact # NOTE: same artifact name
          path: my-file.txt
  upload-again:
    needs: upload
    runs-on: ubuntu-latest
    steps:
      - name: Create a different file
        run: echo "goodbye world" > my-file.txt
      - name: Upload Artifact
-       uses: actions/upload-artifact@v3
+       uses: actions/upload-artifact@v4
        with:
          name: my-artifact # NOTE: same artifact name
          path: my-file.txt
+         overwrite: true

Note that this will create an entirely new Artifact, with a different ID from the previous.

Merging multiple artifacts

In v3, multiple uploads from multiple jobs could be done to the same Artifact. This would result in a single archive, which could be useful for sending to upstream systems outside of Actions via API or UI downloads.

jobs:
  upload:
    strategy:
      matrix:
        runs-on: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.runs-on }}
    steps:
      - name: Create a File
        run: echo "hello from ${{ matrix.runs-on }}" > file-${{ matrix.runs-on }}.txt
      - name: Upload Artifact
        uses: actions/upload-artifact@v3
        with:
          name: all-my-files # NOTE: same artifact name
          path: file-${{ matrix.runs-on }}.txt

The single all-my-files artifact would contain the following:

.
  ∟ file-ubuntu-latest.txt
  ∟ file-macos-latest.txt
  ∟ file-windows-latest.txt

To achieve the same in v4 you can change it like so:

jobs:
  upload:
    strategy:
      matrix:
        runs-on: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.runs-on }}
    steps:
      - name: Create a File
        run: echo "hello from ${{ matrix.runs-on }}" > file-${{ matrix.runs-on }}.txt
      - name: Upload Artifact
        uses: actions/upload-artifact@v3
        with:
-         name: all-my-files
+         name: my-artifact-${{ matrix.runs-on }}
          path: file-${{ matrix.runs-on }}.txt
+ merge:
+   runs-on: ubuntu-latest
+   needs: upload
+   steps:
+     - name: Merge Artifacts
+       uses: actions/upload-artifact/merge@v4
+       with:
+         name: all-my-files
+         pattern: my-artifact-*

Note that this will download all artifacts to a temporary directory and reupload them as a single artifact. For more information on inputs and other use cases for actions/upload-artifact/merge@v4, see the action documentation.