Multi platform worklow using matrix and platform specific step.

[voidcontext]

Hello,

I have a matrix workflow that runs on amd64 and arm64 platforms, there 2 steps that I only want to run on amd64, but it seems these steps don't run on any platforms, what am I missing? Both the server and the agents are on 3.8.0 and the workflow looks like this:

variables:
  - common_settings: &common_settings
      binary_cache: https://cache.nix.vdx.hu/private
      binary_cache_public_key: private:O0/Z0BQZpKKHQQES65u7xNfZF7eCZoz9RKJi191TGaM=
      binary_cache_token:
        from_secret: attic_token
  - runner_image: &runner_image
      image: harbor.vdx.hu/voidcontext/woodpecker-plugin-nix-attic:0.3.0-alpha15

when:
  - event: push
    branch: main
  - event: pull_request

matrix:
  platform:
    - linux/amd64
    - linux/arm64

labels:
  platform: ${platform}

steps:
  - name: cache-warmup
    <<: *runner_image
    settings:
      <<: *common_settings
      script: make cache-warmup

  - name: flake-check
    <<: *runner_image
    when:
      - platform: linux/amd64
    settings:
      <<: *common_settings
      script: nix flake check

  - name: formating-check
    <<: *runner_image
    when:
      - platform: linux/amd64
    settings:
      <<: *common_settings
      script: nix develop -c alejandra . --check

[qwerty287]

I guess that's a bug and this is not supported in it's current state.

The System.Platform field of the metadata is set to an empty string when compiling the pipeline. At that point, the when is evaluated. The problem is that at this point the server doesn't know on which platform this will run. The env var is set by the agent later.

Solving this will probably be pretty hard and requires refactorings on the whole compiling and filtering process.

To solve this for you, the only way I see is to check the CI_SYSTEM_PLATFORM env var and exit early if it's not linux/amd64 (as you're using a plugin you would have to directly implement that logic in the plugin).

[voidcontext]

It seems the docs are a bit misleading, because according to these, it should work (unless I misunderstood something):

• https://woodpecker-ci.org/docs/usage/workflow-syntax#platform
• https://woodpecker-ci.org/docs/usage/matrix-workflows#example-matrix-pipeline-using-multiple-platforms

I guess I should open bug ticket then.

[zc-devs]

variables:
  - common_settings: &common_settings
      binary_cache: https://cache.nix.vdx.hu/private
      binary_cache_public_key: private:O0/Z0BQZpKKHQQES65u7xNfZF7eCZoz9RKJi191TGaM=
      binary_cache_token:
        from_secret: attic_token
  - runner_image: &runner_image
      image: harbor.vdx.hu/voidcontext/woodpecker-plugin-nix-attic:0.3.0-alpha15

when:
  - event: push
    branch: main
  - event: pull_request

matrix:
  include:
    - platform: linux/amd64
      PLATFORM_FOR_FILTER: amd
    - platform: linux/arm64
      PLATFORM_FOR_FILTER: arm

labels:
  platform: ${platform}

steps:
  - name: cache-warmup
    <<: *runner_image
    settings:
      <<: *common_settings
      script: make cache-warmup

  - name: flake-check
    <<: *runner_image
    when:
      evaluate: 'PLATFORM_FOR_FILTER == "amd"'
    settings:
      <<: *common_settings
      script: nix flake check

  - name: formating-check
    <<: *runner_image
    when:
      evaluate: 'PLATFORM_FOR_FILTER == "amd"'
    settings:
      <<: *common_settings
      script: nix develop -c alejandra . --check

[voidcontext]

Thank you for the idea! Actually it can be simplified to:

...

matrix:
  platform:
    - linux/amd64
    - linux/arm64

labels:
  platform: ${platform}

steps:
  - name: cache-warmup
    <<: *runner_image
    settings:
      <<: *common_settings
      script: make cache-warmup

  - name: flake-check
    <<: *runner_image
    when:
      - evaluate: platform == "linux/amd64"
    settings:
      <<: *common_settings
      script: nix flake check

  - name: formating-check
    <<: *runner_image
    when:
      - evaluate: platform == "linux/amd64"
    settings:
      <<: *common_settings
      script: nix develop -c alejandra . --check