How to download a Azure-Devops Pipeline Artifact into a different pipeline - azure-devops

Question

I need to modify an existing YAML pipeline so that it downloads an artifact published from another existing ADO pipeline. The other pipeline is a Classic one in case it matters.
In the current setup, a daily Release pipeline takes the artifact from the Classic pipeline and pushes it to a company repository external to ADO.
Now, the YAML pipeline is only run occasionally and it is run manually. Currently it downloads the artifact from the external repo to which the Release pipeline pushed. This hasn't been a problem generally. However a recent issue highlighted that it would be desirable to be able to avoid the delays built in to the current approach and essentially just grab the artifact directly from the latest run of the Classic pipeline.
When I set out to do this, I assumed that it would be straightforward but I seem to have run into a brick wall. The only information I have found describes using DownloadPipelineArtifact#2 but this depends on various IDs like the pipeline ID and run ID which it seems are not easily obtainable.
I am pretty new to ADO. I'm not a devops person at all really but I've had this put on my plate. So before I spend too much time on this, am I missing something or is this just something that one should not really be doing in ADO? If it is possible, is there a guide somewhere?
UPDATE
Thanks to a useful answer from daniel-mann, I was able to get this working but there were some quirks that I thought I should mention in the event that they might be useful to anyone else.
When I started adding the DownloadPipelineArtifact#2 task (this was editing directly in ADO on a browser), ADO was hinting field names to me that seemed to be different from the documented ones. Possibly these were aliases but I had a hard time knowing what to trust with respect to documentation.
I also noticed a Settings "link" had appeared above the first line of the task definition. When I clicked on this it opened up an editor to the right of the page that helped fill in the fields. It provided dropdowns for things like the project and the pipeline ID.
This what I ended up with:
- task: DownloadPipelineArtifact#2
displayName: "my task description"
inputs:
buildType: 'specific'
project: <long "UID" string identifying project>
definition: <numeric id for pipeline>
buildVersionToDownload: 'latest'
artifactName: <name of artifact as defined in upstream pipeline>
targetPath: '$(Pipeline.Workspace)'
Note that the editor tool added a definition field, but apparently this is an alias for pipeline. I am not sure why it thinks this is more helpful.
Unfortunately the above did not work. I saw this error:
##[error]Pipeline Artifact Task is not supported in on-premises. Please use Build Artifact Task instead.
I don't know what caused this - perhaps the ADO setup in my organization? As I understand it the Build Artifact Task is deprecated in favour of the Pipeline Artifact Task but I did not have any choice but to try it and this time it did work for me.
This time I used the "Settings" editor from the outset and ended up with this:
- task: DownloadBuildArtifacts#0
displayName: "my task description"
inputs:
buildType: 'specific'
project: $(System.TeamProjectId)
pipeline: <numeric ID as above>
buildVersionToDownload: 'latest'
downloadType: 'single'
artifactName: '$(ARTNAME)'
downloadPath: '$(System.ArtifactsDirectory)'
The fields that I manually edited here were:
using our own ARTNAME variable that is we define to be the artifact name in one of our variable groups. The relevant variable group is imported to this pipeline.
using the builtin System.TeamProjectId for the project name. This seemed prefereable to having the "UID" string in there. (Though I also found that the normal name string for our project worked here too.)

Answer 1

but this depends on various IDs like the pipeline ID and run ID
Not for your use case.
You said
just grab the artifact directly from the latest run of the Classic pipeline.
In which case, referring to the parameters explained in the documentation,
# Download pipeline artifacts
# Download build and pipeline artifacts
- task: DownloadPipelineArtifact#2
inputs:
#source: 'current' # Options: current, specific
#project: # Required when source == Specific
#pipeline: # Required when source == Specific
#preferTriggeringPipeline: false # Optional
#runVersion: 'latest' # Required when source == Specific# Options: latest, latestFromBranch, specific
#runBranch: 'refs/heads/master' # Required when source == Specific && RunVersion == LatestFromBranch
#runId: # Required when source == Specific && RunVersion == Specific
#tags: # Optional
#artifact: # Optional
#patterns: '**' # Optional
#path: '$(Pipeline.Workspace)'
You would just need to set the project, pipeline, source: specific, and runVersion: latest parameters.
Or you could use the download alias, which is a little bit simpler but can achieve the same thing