Azure DevOps YAML Pipeline Parameters Not Working from REST API Trigger

Question

I\'m trying to create a YAML based pipeline that takes a parameter, then trigger the pipeline to run from a Azure DevOps REST API. I\'m able to see the build gets queued, but th

Answer 1

I ran into the exact same problem - a pipeline taking runtime parameters that worked when run via the UI, but not via the Queue Build REST API.

I was able to solve this by using an undocumented API, the exact same one that the Az DevOps Pipelines UI calls when running a pipeline:

https://dev.azure.com/{organization}/{project}/_apis/pipelines/{pipelineId}/runs?api-version=5.1-preview

With the following POST body:

{
  "stagesToSkip": [],
  "resources": {
    "repositories": {
      "self": {
        "refName": "refs/heads/master"
      }
    }
  },
  "templateParameters": {
    "testParam": "hello world"
   },
  "variables": {}
}

Note that with this API, your runtime parameters are being submitted as actual JSON, not stringified JSON, and under the key templateParameters.

As well, don't forget to include the standard headers one might expect for this call:

• Content-Type: application/json
• Accept: application/json
• AUTHORIZATION: bearer $SYSTEM_ACCESSTOKEN.

Using this approach, in the called pipeline, you will always be able to access the value of ${{ parameters.testParam }} whether the pipeline is called via REST API or manually in the UI.

While you're correct that the value is accessible as $(testParam) when executed via REST API, that variable is not populated when running the pipeline in the UI.

As such, I'd recommend using this undocumented API, since the called pipeline can use ${{ parameters.testParam }} without regard to how it's being called. Of course, it's (as of writing) undocumented, so.... ¯_(ツ)_/¯

As well, it should be noted that your pipeline must be formatted as @Josh Gust suggested:

my-template.yaml:

parameters:
  - name: testParam
    type: string
    default: 'N/A'
steps:
  - script: echo ${{ parameters.testParam }}

azure-pipelines.yaml:

parameters:
  - name: testParam
    type: string
    default: 'N/A'
trigger:
  - master
extends:
  template: my-template.yaml
  parameters:
    testParam: ${{ parameters.testParam }}