Output artifact in same location as optional input artifact is not saved

[samath117]

Is this a BUG REPORT or FEATURE REQUEST?: BUG REPORT

What happened: When an output artifact location matches that of an optional input artifact which is not supplied, the output artifact fails to save properly. This is related to #1503 and #1660.

How to reproduce it (as minimally and precisely as possible):

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: optional-input-output-artifact-same-location-
spec:
  entrypoint: plan
  templates:
  - name: plan
    steps:
    - - name: write
        template: file
    - - name: read
        template: file
        arguments:
          artifacts:
          - name: file
            from: "{{steps.write.outputs.artifacts.file}}"
  - name: file
    inputs:
      artifacts:
      - name: file
        path: /tmp/file1.txt
        optional: true
    container:
      image: alpine:latest
      command: [sh, -c]
      args: ["echo 'test' > /tmp/file1.txt"]
    outputs:
      artifacts:
      - name: file
        path: /tmp/file1.txt

When this is run, the write step passes, but the read step fails with this message: inputs.artifacts.file was not supplied. If the location of the optional input file is changed to /tmp/file2.txt, then both steps pass. This indicates that the output artifact is failing to save properly, but isn't raising an error in the process even though it isn't labeled as optional.

Environment: Argo version: 2.4.1

[samath117]

Update: In v2.7.5, this example still fails, but on the write step and with a different error:
failed to save outputs: stat /mainctrfs/tmp/file1.txt: no such file or directory

[alexec]

@simster7 are you looking into this please? If not, I would like to.

[simster7]

Yes I am, was planning to start on this after closing my open PRs

[alexec]

Cool- Thank you