Getting the approver for release to an environment within an Azure DevOps Multi-Stage YAML pipeline

I recently had the need to get the email address of the approver of a deployment to an environment from within a multi-stage YAML pipeline. Turns out it was not as easy as I might have hoped given the available documented APIs.

Background

My YAML pipeline included a manual approval to allow deployment to a given environment. Within the stage protected by the approval, I needed the approver's details, specifically their email address.

I managed to achieve this but had to use undocumented API calls. These were discovered by looking at Azure DevOps UI operations using development tools within my browser.

The Solution

The process was as follows

• Make a call to the build's timeline to get the current stage's GUID - this is documented API call
• Make a call to the Contribution/HierarchyQuery API to get the approver details. This is the undocumented API call.

The code to do this is as shown below. It makes use of predefined variables to pass in the details of the current run and stage.

Note that I had to re-create the web client object between each API call. If I did not do this I got a 400 Bad Request on the second API call - it took me ages to figure this out!