"Shift" option doesn't accept zero

[noltron000]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Affected packages and versions

v1.02

Link to runnable example

No response

Steps to reproduce

Use {shift: 0} as an option in the this module.
IE,

const vFile = await rehype( )
  .use(rehypeParse, {fragment: true})
  .use(rehypeShiftHeading, {shift: 0})
  .use(rehypeSanitize, rehypeSanitizerSchema)
  .use(rehypeReact, rehypeReactOptions)
  .process(html)

Expected behavior

It shouldn't throw an error, even though technically the function shouldn't do anything to the tree either, with a shift value of zero.

Actual behavior

There is an error thrown: Error: Missing required `shift` in options.

You can see why this behavior is happening:

rehype-shift-heading/index.js

Line 18 in 5bab36b

if (!options || !options.shift) {

Zero is falsey, so it isn't an accepted value.

Runtime

No response

Package manager

No response

OS

No response

Build and bundle tools

No response

[noltron000]

As to why we would want this, there are times our HTML headings might be on the right level already, and other times where it is not. We could pass in a variable shift value instead of setting it at zero as I did in the ticket above. (IE (html, shift) => rehype( ).use(rehypeShiftHeading, {shift}) or something)

[wooorm]

Yeah that was my next question lol. Open to a PR for this, I understand the use case :)

[noltron000]

Yeah! No problem and thanks for the fast response. Its not a big deal and can be worked around by setting the options object to false to turn the plugin off, instead of {shift: 0} or whatever, for example

const processHTML = async (
  html: string,
  options?: Options,
) => {

  // ...

  // Bypass zeroes not being accepted in this method.
  let shiftHeadingOptions
  if (options?.shift == null || options.shift === 0) shiftHeadingOptions = false
  else shiftHeadingOptions = {shift: options.shift}

  // ...

  const vFile = await rehype( )
    .use(rehypeShiftHeading, shiftHeadingOptions)
    .use( // ...etc
}

[wooorm]

For the PR: you should add a test, and then: don't walk the tree on 0, that would be useless!

[wooorm]

done!