Consider removing React rendering behaviour altogether

[motiz88]

Questions following #26 and in relation to #30 which I'm currently working on:

Is pretty-format's React element plugin not sufficient? Why do we need to actually render components? Or to put it another way, why diverge from .toMatchSnapshot()'s behaviour? I would definitely prefer a (semver-major) change to remove this logic.

[thymikee]

The main reason we do this, was to get rid of tedious renderer.create().toJSON() part, and make it as easy to snapshot components as possible. You should still be able to feed snapshot-diff with code like this, if you want consistency with regular snapshots.

[motiz88]

I would question the ergonomics of this for someone coming from Jest. It doesn't satisfy the principle of least surprise, IMHO. Especially if over time we want this to have more Jest-like features, e.g. #30.

In my ideal world, refactoring between regular snapshots and diff snapshots should be a no-brainer, as if this was a core Jest API*:

expect(a).toMatchSnapshot();
expect(b).toMatchSnapshot();
// ↑ ↓
expect(snapshotDiff(a, b)).toMatchSnapshot();

Except currently, if a and b are React elements, fundamentally different things happen.

The rendering behaviour can be migrated to an opt-in serializer with #30, so there's an upgrade path for users currently relying on it (which is not everyone - #20).

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* To the point where, if there was a hygienic way for us to just reuse Jest's config for #30, I would have preferred that btw - but that's off-topic here.

[thymikee]

You've got the point. Ideas how can we support both use cases? We should be able to support both use cases

[motiz88]

With the proposed API of #30:

const reactRenderSerializer = require("snapshot-diff/reactRenderSerializer");
// NOTE: This can just be a separate package now

const snapshotDiff = require("snapshot-diff").withSerializers(
  [reactRenderSerializer]
);
snapshotDiff(<A />, <B />);

This behaviour around aAnnotation and bAnnotation would be harder to replicate. Note that any user-set values are already being ignored now, which is itself weird.

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This leads me to think the React rendering and diffing function should actually be its own package, e.g. a snapshot-diff-react that uses snapshot-diff but adds a default serializer and sets the annotations itself.