How to create a comment in Azure DevOps PR in case of build failure?

I can help with an example. There is a bunch of value in posting custom messages\status to PRs from your pipelines.

First things first, make sure your build service has permissions to contribute to pull requests in your repository.

Then you want to add a conditional PowerShell step. This one is just based on it being a PR build, but you might want to add a depends on failure for the previous step, based on your workflow.

- task: PowerShell@2  condition: eq(variables['Build.Reason'], 'PullRequest')  displayName: Post Message to PR  env:    SYSTEM_ACCESSTOKEN: $(System.AccessToken)    inputs:      targetType: filePath      filePath: PostToPR.ps1

So the basic workflow is:

• Build the Markdown Message
• Build the JSON Body
• Post the Message to the PR

PostToPR.ps1

#Going to create the comment in an Active state, assuming it needs to be resolved#See https://docs.microsoft.com/en-us/dotnet/api/microsoft.teamfoundation.sourcecontrol.webapi.commentthreadstatus?view=azure-devops-dotnet$StatusCode = 1 $Stuff = $env:Build_Repository_Name$Things = "Other things you might want in the message"#Build Up a Markdown Message to $Markdown = @"## Markdown Message here|Column0 |Column1||--------|---------||$Stuff|$Things|  "@#Build the JSON body up$body = @"{    "comments": [      {        "parentCommentId": 0,        "content": "$Markdown",        "commentType": 1      }    ],    "status": $StatusCode   }"@Write-Debug $Body#Post the message to the Pull Request#https://docs.microsoft.com/en-us/rest/api/azure/devops/git/pull%20request%20threads?view=azure-devops-rest-5.1try {    $url = "$($env:SYSTEM_TEAMFOUNDATIONCOLLECTIONURI)$env:SYSTEM_TEAMPROJECTID/_apis/git/repositories/$($env:Build_Repository_Name)/pullRequests/$($env:System_PullRequest_PullRequestId)/threads?api-version=5.1"    Write-Host "URL: $url"    $response = Invoke-RestMethod -Uri $url -Method POST -Headers @{Authorization = "Bearer $env:SYSTEM_ACCESSTOKEN"} -Body $Body -ContentType application/json  if ($response -ne $Null) {    Write-Host "*******************Bingo*********************************"  }}catch {  Write-Error $_  Write-Error $_.Exception.Message}

And you end up with a nice markdown table with custom status information in your PR!

Building on the great answers already provided, this is the equivalent inline YAML pipeline script:

  - powershell: |      $body = @"      {          "comments": [            {              "parentCommentId": 0,              "content": "Your comment here",              "commentType": 1            }          ],          "status": 4        }      "@      $url = "$($env:SYSTEM_TEAMFOUNDATIONCOLLECTIONURI)$env:SYSTEM_TEAMPROJECTID/_apis/git/repositories/$($env:Build_Repository_Name)/pullRequests/$($env:System_PullRequest_PullRequestId)/threads?api-version=5.1"      $result = Invoke-RestMethod -Uri $url -Method POST -Headers @{Authorization = "Bearer $(System.AccessToken)"} -Body $Body -ContentType application/json    displayName: Post comment on PR

If you mean creating PR comment in the build pipeline, then you can add a PowerShell task in your pipeline and run the script to call the REST API (Pull Request Thread Comments - Create).

Below PowerShell script for your reference:

Param(   [string]$baseurl = "https://dev.azure.com/{organization}",   [string]$projectName = "0508-t",   [string]$repositoryId = "62c8ce54-a7bb-4e08-8ed7-40b27831bd8b",   [string]$pullRequestId = "35",   [string]$threadId = "229",   [string]$user = "",   [string]$token = "PAT"  )# Base64-encodes the Personal Access Token (PAT) appropriately$base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f $user,$token)))write-host $WorkitemType#Create Jason bodyfunction CreateJsonBody{    $value = @"{  "content": "Test Comment 0204",  "parentCommentId": 1,  "commentType": 1}"@ return $value}$json = CreateJsonBody$uri = "$baseurl/$projectName/_apis/git/repositories/$repositoryId/pullRequests/$pullRequestId/threads/$threadId/comments?api-version=5.1"Write-Host $uri$result = Invoke-RestMethod -Uri $uri -Method Post -Body $json -ContentType "application/json" -Headers @{Authorization=("Basic {0}" -f $base64AuthInfo)}