add create mode

[mildfuzz]

No description provided.

[GrayedFox]

I think it's worth zooming out a bit here and deciding whether or not the pdf-visual-diff tool should be the thing that handles throwing/failing a test, or if it should instead expose some functionality that the test runner (mocha, jest, Cypress, etc) can plug into.

If applying the single responsibility principle to the configuration option I think it might make sense to have two distinct, separate boolean values that can be on/off in any combination. Forgive the names, likely some clearer and simpler variable names that could be used, just pressed for time at the moment, example uses JSON schema syntax:

{
  "options": {
    "generateIfSnapshotMissing": {
      "type": "boolean",
      "description": "Whether or not generating a snapshot should be done if one is missing",
      "default": true
    },
    "failIfSnapshotMissing": {
      "type": "boolean",
      "description": "Whether or not a missing snapshot should result in a failed check",
      "default": false
    }
  }
}

This way people are free to use them in any combination, i.e. if generating a snapshot is unexpected (due to it being part of a normal run) pdf-visual-diff will see there's no matching snapshot, fail the comparison, and the resulting boolean can be used by the test writer to act on.

Assuming the above was implemented and taking advantage of these modes @mildfuzz would this come close to your desired behaviour? Example uses node environment variables but could also be done programatically:

//package.json
{
  scripts: {
        generatePdfs: "PVD_FAIL_IF_SNAPSHOT_MISSING=false PVD_GENERATE_IF_SNAPSHOT_MISSING=true jest ./specs/ || false",
        test: "PVD_FAIL_IF_SNAPSHOT_MISSING=true PVD_GENERATE_IF_SNAPSHOT_MISSING=false jest ./specs/",
    }
}

In our case we have multiple PDF checks done in a single context() block so allowing the test runner to continue and not fail that block in order to continue to generate PDFs is useful for us, even though when we do generate PDFs we want to output an non-zero status code when all tests pass anyway, which we do by fudging the exit code using the || false bash trick 🙈

[moshensky]

I like this proposal.
@mildfuzz do you think it would be useful to you as defined above by @GrayedFox?

I could also wing it as well.

[mildfuzz]

Yeah, I could certainly do what I need to with this set up, and if it adds further flexibility, all the better

[moshensky]

Yeah, I could certainly do what I need to with this set up, and if it adds further flexibility, all the better

Great! Are you still planning to finish it, or would you prefer if I took it from here? No worries either way, just let me know what works best for you!

[mildfuzz]

I'm unlikely to get free time for this for a week or so, so if you're keen I would be happy for you to take it over

[moshensky]

Closing in favour of the other PR that was merged.