fix: Set env var if it differs from actual value

[david-marconis]

Problem

There is an issue with the current action if you run multiple Trivy actions in a row. It will not respect the inputs as it will not set the env var if the env var if the input value is a different value. However, if the env var already has a different value than the default and you try to set it to a default value, it will not work.

Scenario

Here is a scenario: You first run Trivy scan with sarif format, and then you run with table format:

        - uses: aquasecurity/[email protected]
          with:
            image-ref: node:23.2.0-alpine3.20
            severity: CRITICAL,HIGH
            exit-code: 0
            format: sarif
        - uses: aquasecurity/[email protected]
          with:
            image-ref: node:23.2.0-alpine3.20
            severity: CRITICAL,HIGH
            exit-code: 1
            format: table

Then then the second scan will not use format table, as it uses the previously set env var: TRIVY_FORMAT: sarif.

Tests

Here is a workflow run that shows the issue:
input format: table
https://github.com/david-marconis/trivy-ignore-bug/actions/runs/12065562387/job/33644593462#step:3:6
env TRIVY_FORMAT: sarif
https://github.com/david-marconis/trivy-ignore-bug/actions/runs/12065562387/job/33644593462#step:3:20
log indicating sarif mode:
https://github.com/david-marconis/trivy-ignore-bug/actions/runs/12065562387/job/33644593462#step:3:159

Fix

The fix is to check if the actual value differs from the wanted value. You could also remove the check if it is the same as the default, IDK if this has any other implications.

Here is a workflow run with the fix implemented:
https://github.com/david-marconis/trivy-ignore-bug/actions/runs/12065669260/job/33644932663#step:3:217

Fixes

Fixes this issue #438
Might also fix this #435 and #422

[CLAassistant]

All committers have signed the CLA.

[mkjpryor]

I am also seeing this - it would be great if the fix could be merged and released ASAP.

[simar7]

@DmitriyLewen could you take a look?

[DmitriyLewen]

This helps in your case, but breaks logic for config file (if default value != "").
Let's look at an example - if we don't set format in inputs - we should use format from config file (json in this example):

• master branch - json format - https://github.com/DmitriyLewen/test-trivy-action/actions/runs/12134369796/job/33831459219#step:3:130
• your changes - table format - https://github.com/DmitriyLewen/test-trivy-action/actions/runs/12134373819/job/33831470667#step:3:146

[DmitriyLewen]

What if we will unset all TRIVY_* envs after run Trivy?

[DmitriyLewen]

Hello @david-marconis
I played around with this a bit more today.
It seems we can't unset envs from GITHUB_ENV.

I suggest saving and loading envs to a file (to use them locally in trivy-action).
Check out this branch - https://github.com/DmitriyLewen/trivy-action/commits/fix/overwrite-envs/
and test runs - https://github.com/DmitriyLewen/test-trivy-action/actions/runs/12155043324/job/33896010552

Let me know if you have time to test this and update my pr.
If not - no problem - I'll do it when I have time.

Best regards, Dmitriy