fix: Fix empty toDataURL() in TypeScript

[indianakernick]

The recent change to the toDataURL function made the type parameter required. It was previously optional. This is a breaking change and most likely an innocent mistake.

Additionally, the type of the encoderOptions parameter for the second overload was corrected. The type of type could be string and its value could be 'image/svg+xml'. So ToSVGOptions should be accepted by the encoderOptions parameter. This is not technically a breaking change but it's something I noticed while I was in the area.

[UziTech]

The type of type could be string and its value could be 'image/svg+xml'. So ToSVGOptions should be accepted by the encoderOptions parameter.

The whole point of the overload is so the encoderOptions parameter can be ToSvgOptions only when the type is 'image/svg+xml'

[UziTech]

Can you add a test for toDataURL without a type parameter so this doesn't break again?

[indianakernick]

Can you add a test for toDataURL without a type parameter so this doesn't break again?

Added.

The whole point of the overload is so the encoderOptions parameter can be ToSvgOptions only when the type is 'image/svg+xml'

Yeah. I understand the intent. When type is 'image/svg+xml', encoderOptions must be ToSvgOptions. When it is not 'image/svg+xml', it must be number. It's a bit difficult to express that second part in TypeScript currently. There's no way to say "any string except for 'image/svg+xml'". Because of this, the overload set doesn't really work. For example, this compiles: toDataURL('image/svg+xml', 1). In this case, the second overload is chosen.

As it is defined with and without the changes in this PR, toDataURL doesn't fully enforce correct usage at compile-time. However, the first overload still expresses intent. It still acts as a form of documentation. When I type toDataURL('image/, the IDE suggests that I use 'image/svg+xml' and pass ToSvgOptions as the second argument. There are a few possibilities for improving this.

1. Throw an exception instead of ignoring encorderOptions when the runtime type check fails. This is a breaking change but it breaks code that was already broken so it sort of isn't a breaking change.
2. Remove the SVG overload from toDataURL and instead create a dedicated function that calls toSVG and converts it to a data URL. This is a breaking change.
3. Instead of using string, use a union of all image mime types. So type ImageMimeType = 'image/png' | 'image/svg+xml' .... Then the first overload could use 'image/svg+xml' and the second overload could be Exclude<ImageMimeType, 'image/svg+xml'>. This is also a breaking change. Also, maintaining a complete list of image mime types would be a bit of a pain.

Unless you feel like releasing version 5.0.0 with some breaking changes, it seems like the available options are limited.

[UziTech]

I don't care if they put a number for SVG. It will be handled the same as setting a number for PNG It does nothing. But I don't want ToSVGOption except for SVG.

[UziTech]

Thanks for bringing this to my attention! 💯

[github-actions]

🎉 This PR is included in version 4.1.1 🎉

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