Add YAML anchor and alias support for GitHub Actions workflows

[alexaandru]

Implements two-pass YAML parsing to resolve anchors (&anchor) and aliases (*alias) before linting, matching GitHub Actions' native YAML support.

• Add containsAnchorsOrAliases() to detect anchor usage
• Add resolveYAMLAnchors() using unmarshal/marshal strategy
• Modify Parse() to resolve anchors when present
• Add comprehensive test suite covering various anchor scenarios
• Preserve backward compatibility for workflows without anchors
• Maintain error detection and line number reporting after resolution

Fixes workflows that previously failed with "alias node but mapping node is expected" errors when using YAML anchors supported by GitHub Actions.

Fixes #133

The support for this just landed: actions/runner#1182

[alexaandru]

Please note that both lint and test FAIL but they also FAIL on main branch. This PR didn't introduce any new test failures, they are the same as on main. It did however introduce plenty of tests for the feature and they are all passing.

[ChristopherHX]

I had added anchor support in nektos/act yaml validator a while back at nektos/act#5893

e.g. https://github.com/nektos/act/blob/5e62222f80b8847de5dfced0527eaaeca3303168/pkg/schema/schema.go#L241C1-L243C3 I then traverse over alias and just handle it as if there were no alias.

Some suggestions from my side, using yaml.Node also heavily.

Just do *node = node.Alias and skip a lot of serializing / deserializing?

Otherwise assign node.Alias where you read this node pointer.

if node.Anchor != ""
just do node.Anchor = "" or remove the assert that require this to be cleared if any.

If I didn't produce a big bug in act, then this improves the code in my opinion

Otherwise use yaml.Node.Encode() and yaml.Node.Decode to replace marshall and unmarshall, this would avoid generating a text representation of the yaml that is not needed.

Serializing the yaml.Node into an interface may break diagnostic features of actionlint regardless if you use yaml.Node or text as medium for reading the yaml again.

[alexaandru]

Thank you so much for the help, those are good tips!

[neodc]

Any idea of when this could be merged and released?

[rhysd]

It seems that #557 and #568 has the same goal and different implementations. I need to check both but I don't have enough time for now. Let me check this PR after releasing the next version.

[rhysd]

I'm closing and reopening this PR to kick CI workflows because GitHub seemed to dismiss 'Approve CI' button.

[vivodi]

Can you fix the failing checks? @alexaandru

[rhysd]

Thank you for working on this feature and the approach used in this branch is interesting.

However I found a critical issue that the error position can be completely corrupted and cannot be recovered.

For example

on: push

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - run: env | grep MY_TEST_
        env: &default_env
          INVALID_ENV: []
      - run: env | grep MY_TEST_
        env: *default_env

This workflow causes the following errors:

test.yaml:6:30: expected scalar node for string value but found sequence node with "!!seq" tag [syntax-check]
test.yaml:9:30: expected scalar node for string value but found sequence node with "!!seq" tag [syntax-check]

However the positions 6:30 and 9:30 are actually not indicating the error positions in the original workflow because we parse a converted workflow generated by go-yaml. This issue is critical because users are not able to understand where the errors occurred.