Conditional step for the last value in (dynamically generated) matrix of Github Actions only

Peter Butkovic 0
Viewed 18

I'm trying to conditionally run the job step for the last value of the matrix only.

For demo purposes, the simplified actions file follows.

Please note the simplification: matrix values are static in sample, but I need the solution to work without constants (as the case I'm solving generates these dynamically):

on:
  push:
    branches:
      - main

jobs:
  example_matrix:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        version: [1,2,3]
    steps:
      - run: |
          echo Matrix value: "${{ matrix.value }}"
      - if: ${{fromJson(matrix.version[-1])}} == ${{ matrix.value }}
        run: |
          echo Matrix value (latest): "${{ matrix.value }}"

Please note, the if condition is of my interest, to be corrected. I want it to run for the last element of the matrix.version array only.

Current output:

Error: The template is not valid. Newtonsoft.Json.JsonReaderException: Error reading JToken from JsonReader. Path '', line 0, position 0.
   at Newtonsoft.Json.Linq.JToken.ReadFrom(JsonReader reader, JsonLoadSettings settings)
   at Newtonsoft.Json.Linq.JToken.ReadFrom(JsonReader reader)
   at GitHub.DistributedTask.Expressions2.Sdk.Functions.FromJson.EvaluateCore(EvaluationContext context, ResultMemory& resultMemory)
   at GitHub.DistributedTask.Expressions2.Sdk.ExpressionNode.Evaluate(EvaluationContext context)
   at GitHub.DistributedTask.Expressions2.Sdk.Functions.Format.FormatResultBuilder.<>c__DisplayClass3_0.<Append>b__0()
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.get_Value()
   at GitHub.DistributedTask.Expressions2.Sdk.Functions.Format.FormatResultBuilder.<>c.<ToString>b__1_0(Object obj)
   at System.Linq.Enumerable.SelectListIterator`2.MoveNext()
   at System.String.Join(String separator, IEnumerable`1 values)
   at GitHub.DistributedTask.Expressions2.Sdk.Functions.Format.FormatResultBuilder.ToString()
   at GitHub.DistributedTask.Expressions2.Sdk.Functions.Format.EvaluateCore(EvaluationContext context, ResultMemory& resultMemory)
   at GitHub.DistributedTask.Expressions2.Sdk.ExpressionNode.Evaluate(EvaluationContext context)
   at GitHub.DistributedTask.Expressions2.Sdk.Operators.And.EvaluateCore(EvaluationContext context, ResultMemory& resultMemory)
   at GitHub.DistributedTask.Expressions2.Sdk.ExpressionNode.Evaluate(EvaluationContext context)
   at GitHub.DistributedTask.Expressions2.Sdk.ExpressionNode.GitHub.DistributedTask.Expressions2.IExpressionNode.Evaluate(ITraceWriter trace, ISecretMasker secretMasker, Object state, EvaluationOptions options)
   at GitHub.DistributedTask.ObjectTemplating.Tokens.TemplateToken.EvaluateTemplateToken(TemplateContext context, String expression, Int32& bytes)
   at GitHub.DistributedTask.ObjectTemplating.Tokens.BasicExpressionToken.EvaluateTemplateToken(TemplateContext context, Int32& bytes)
   at GitHub.DistributedTask.ObjectTemplating.TemplateUnraveler.RootBasicExpression()
github-actions
1 Answers

OK, haven't found a way to achieve it via conditional step => ended up with the 3 actions in total, where one publishes full array in 1 variable and last element in another one. job2 creates the matrix on full array and job3 on the last element only.

See my solution:

on:
  push:
    branches:
      - main

jobs:
  job1:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.matrix.outputs.matrix }}
      last: ${{ steps.matrix.outputs.last }}
    steps:
      - id: matrix
        run: |
          echo "::set-output name=matrix::[\"1\",\"2\"]"
          echo "::set-output name=last::[\"2\"]"

  job2:
    needs: [ job1 ]
    runs-on: ubuntu-latest
    strategy:
      matrix:
        value: ${{fromJson(needs.job1.outputs.matrix)}}
    steps:
      - run: |
          echo Current: "${{ matrix.value }}"

  job3:
    needs: [ job1 ]
    runs-on: ubuntu-latest
    strategy:
      matrix:
        value: ${{fromJson(needs.job1.outputs.last)}}
    steps:
      - run: |
          echo Current: "${{ matrix.value }}"
Peter Butkovic0
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