Azure Devops: Is it possible to nest yaml templates inside another yaml template?

Question

Is it possible to nest yaml templates inside another yaml template ?

I've multiple NuGet projects in different Git repository, and I'm trying to template the process of publishing NuGets on nuget.org.

So I created a git repository named "devops-templates", did a first yaml template, be sure that it works, then divide it 4 yaml templates (build solution, generate packages, run unit tests, publish), and reference them into the global yaml template.

The problem is that when I tried to use this global template into my pipelines, I obtained errors

/Net/Utilities/BuildSolution.yml@templates (Line: 33, Col: 18): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 36, Col: 21): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 48, Col: 24): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 53, Col: 28): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 54, Col: 26): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 59, Col: 21): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 60, Col: 22): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 61, Col: 32): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 63, Col: 21): A template expression is not allowed in this context,/Net/Utilities/BuildSolution.yml@templates (Line: 64, Col: 26): A template expression is not allowed in this context

I searched inside Microsoft documentation : https://docs.microsoft.com/en-us/azure/devops/pipelines/process/templates?view=azure-devops but didn't find any information about it.

Here some parts of my code:

azure-pipelines.yml (main repository):

resources:
  repositories:
    - repository: templates
      type: github
      name: (...)/devops-templates
      ref: refs/tags/v1.1.0
      endpoint: (...)

stages:
- template: Net/Pipeline/NuGetsPipeline.yml@templates
  parameters:
    solution: $(solution)
    nuGetsArtifactName: $(nuGetsArtifactName)
    buildArtifactName : $(buildArtifactName)
    (...)

NuGetsPipeline.yml (devops-templates repository):

parameters:
 nuGetsArtifactName: 'NuGets'
 buildArtifactName : 'Build'
 nuGetSource: https://api.nuget.org/v3/index.json
 solution: ''
 (...)

stages:

- stage: Build
  jobs:
  - template: ${{variables['System.DefaultWorkingDirectory']}}/Net/Utilities/BuildSolution.yml
    parameters:
      buildArtifactName : ${{ parameters.buildArtifactName }}
      (...)

  - template: ${{variables['System.DefaultWorkingDirectory']}}/Net/Utilities/GenerateNuGets.yml
    parameters:
      nuGetsArtifactName: ${{ parameters.nuGetsArtifactName }}
      buildArtifactName : ${{ parameters.buildArtifactName }}
      (...)

- stage: 'UnitTests'
  jobs:
  - template: ${{variables['System.DefaultWorkingDirectory']}}/Net/Utilities/RunUnitTests.yml
    parameters:
      buildArtifactName : ${{ parameters.buildArtifactName }}
      (...)

- stage: 'Publish'
  jobs:
  - template: ${{variables['System.DefaultWorkingDirectory']}}/Net/Utilities/PublishNuGets.yml
    parameters:
      nuGetsArtifactName: ${{ parameters.nuGetsArtifactName }}
      (...)

BuildSolution.yml (devops-template repository):

parameters:
  buildArtifactName: 'Build'
  solution: ''
  (...)

  jobs:
  - job: 'BuildSolution'
    pool:
        vmImage: ${{ parameters.vmImage }}
    continueOnError: false
    variables:
      artifactName: ${{ parameters.buildArtifactName }}
    steps:
      - task: NuGetCommand@2
        displayName: 'Restore NuGet packages'
        inputs:
          restoreSolution: ${{ parameters.solutionDir }}/${{ parameters.solution }}
          configuration: ${{ parameters.buildConfiguration}}

      - task: VSBuild@1
        (...)

Edit : I added some parts of my code.

Answer 1

It seems like there is an indentation mistake in your BuildSolution.yml. parameters and jobs should have the same indentation. refer to below:

parameters:
  buildArtifactName: "build"
  solution: ""

jobs:
- job: 'BuildSolution'
  pool:
    vmImage: ${{parameters.vmImage}}
    continueOnError: false
  variables:
    artifactName: ${{ parameters.buildArtifactName}}
  steps:
    - task: NuGetCommand@2
      displayName: 'Restore NuGet packages'
      inputs:
        restoreSolution: ${{ parameters.solutionDir }}/${{ parameters.solution }}
        configuration: ${{parameters.buildConfiguration}}

Answer 2

You can reference four kinds of templates within Azure Pipelines: Stage, Job, Step and Variable.

An example (with slightly modified comments by me) taken from the "Template References" documentation is as follows:

# File: azure-pipelines.yml which references another YAML file (test.yml)

stages:
- template: stages/test.yml  # Template reference
  parameters:
    name: Mini
    testFile: tests/miniSuite.js

- template: stages/test.yml  # Template reference
  parameters:
    name: Full
    testFile: tests/fullSuite.js

And the test.yml file is as follows:

# File: test.yml file to be referenced by the azure-pipelines.yml file

parameters:
  name: ''
  testFile: ''

stages:
- stage: Test_${{ parameters.name }}
  jobs:
  - job: ${{ parameters.name }}_Windows
    pool:
      vmImage: vs2017-win2016
    steps:
    - script: npm install
    - script: npm test -- --file=${{ parameters.testFile }}
  - job: ${{ parameters.name }}_Mac
    pool:
      vmImage: macos-10.13
    steps:
    - script: npm install
    - script: npm test -- --file=${{ parameters.testFile }}