Add curly braces when attribute shorthand is used but not allowed

[jesseskinner]

Closes #110

I also added the ability for custom options in formatting tests, which was needed to reproduce this bug.

[benmccann]

@jesseskinner just fyi - I don't know enough to review the PRs in this repo. I just noticed that one issue and thought I'd point it out

[jesseskinner]

@benmccann No problem! Thanks for catching that.

[ehrencrona]

I think I'd find it more readable if you instead had a completely separate branch for the attribute shorthand case, i.e.

if (isAttributeShorthand) {
    if (options.svelteAllowShorthand) {
        return concat([line, '{', node.name, '}']);
    }
    else {
        return concat([line, node.name, '="{', node.name, '}"']);
    }
} else { ... }

But your solution works fine too, so LGTM

[dummdidumm]

Thanks for this! Could you resolve the merge conflicts and apply the refactoring suggestion from @ehrencrona which makes it more readable? I'm happy to merge this in then.

[jesseskinner]

@dummdidumm Done & done. The refactoring broke an old test, and that revealed that svelteStrictMode came into play here too, so I added the extra test case. With "svelteStrictMode": true, it will change <input {value} /> to <input value="{value}" /> whereas "svelteAllowShorthand": false would only necessitate changing it to <input value={value} /> (without the quotes).

[dummdidumm]

Thanks, all looking good! I refactored the other branch to make that one more readable, too, and added some more tests.