Prettier 1.15, jsxSingleQuote and inline snapshots

[borekb]

I'm trying Jest with the newly released Prettier 1.15 that supports jsxSingleQuote. I have set it to true in my .prettierrc and after running Jest, tests look like this:

it('...', () => {
    const tree = renderer.create(<Link to='/'>Example</Link>).toJSON();
    expect(tree).toMatchInlineSnapshot(`
<Link
  to="/"
>
  Example
</Link>
`);
});

I've got two questions here:

1. Is it expected that Jest applies Prettier to the entire file? We don't use Prettier in this project, I was sort of assuming Jest only runs the snapshots through Prettier but before I updated to 1.15, I was getting <Link to="/"> on line 2.
2. Is it expected that the snapshots themselves get double quotes? All tests are passing but it seems a bit strange.

Thanks.

[SimenB]

1. Yes, formatting just the snapshot part proved difficult,/cc @azz
2. Yes, the serialization has nothing to do with prettier, that's done by pretty-format

[borekb]

Thanks. I have to admit though that at this point I don't quite understand why Jest needs to format my source code – what would happen if I, for example, used different JSX quotes inside my renderer.create snippet?

[SimenB]

We don't format jsx, we format the result from React.createElement passed through some render function.

For prettier discussion, please see #6380

[borekb]

Oh, I probably understand now, it took me a while :) So when Jest transforms this:

expect(tree).toMatchInlineSnapshot();

to this:

expect(tree).toMatchInlineSnapshot(`
<Example>hello</Example>
`);

it does so by reading my source file into AST via Prettier, appending the snapshot in it and calling prettier.format, right? That's pretty drastic but I can understand why it was easier than doing string manipulation (though it doesn't seem like a very complex one..).

Thanks!

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