How to use Azure DevOps REST API to post link in PR comments from Azure Pipeline?

parameters:
      comment: >
        {
          "comments": [
            {
              "parentCommentId": 0,
              "content": "<a href\=\"$(taskUrl)\">Click here to see colored output of Terraform plan:</a>\\n\`\`\`hcl$(plan)\`\`\`",
              "commentType": "system"
            }
          ],
          "status": "byDesign"
        }

...some template...

  curl --fail \
    --request POST "$URL" \
    --header "Authorization: Bearer ${{ parameters.accessToken }}" \
    --header "Content-Type: application/json" \
    --data @- <<- EOF
  ${{ parameters.comment }}
  EOF

This is my code, doesn't work.

I think Azure Pipelines is sanitizing my code, when I inspect the element there's nothing after href, completely deleted.

At the same time, I've tried with Markdown [example](https://link.com), but I get parsing error due to ().

Tried escaping them, but this also doesn't work. I actually tried everything I could think of for one week straight. Couldn't find any solution

I have no issues commenting on the PR using the script you provided. I suspect the value of your variable $(taskUrL) doesn't have a value.

In the following template, I'm using a job template so that I can write the variables into the job.

parameters:
- name: taskUrl
  type: string

- name: hclPlan
  type: string

- name: comment
  type: string
  default: |-
    {
      "comments": [
        {
        "parentCommentId": 0,
          "content": "<a href=\"$(taskUrl)\">$(hclPlan)</a>",
          "commentType": "system"
        }
      ],
      "status": "byDesign"
    }

jobs:
- job: displayjob
  variables:
    taskUrl: ${{ parameters.taskUrl }}
    hclPlan: ${{ parameters.hclPlan }}
  steps:
  - script: |
      baseUrl="$(System.TeamCollectionUri)/$(System.TeamProject)"
      apiUrl="/_apis/git/repositories/$(Build.Repository.Id)/pullRequests/$(System.PullRequest.Id)/threads?api-version=6.0"
      url = $baseUrl$apiUrl
      curl --fail \
        --request POST "$url" \
        --header "Authorization: Bearer $(System.AccessToken)" \
        --header "Content-Type: application/json" \
        --data @- <<- EOF
      ${{ parameters.comment }}
      EOF

Under the hood, here's the order of operations:

1. At compile time, the template is expanded and the values of the expressions are written into the YAML. At this time $(taskUrl) has no value because it's a runtime value.
2. The script task pre-processes the inline script as it appears in the YAML and replaces all references of variables written in macro syntax $(<variable-name>) with their runtime values.
3. The script task writes the resulting script to disk as a temporary file and then executes it.