the head config to support function in doc theme

[Djuki]

@shuding I was solving my issue described here #379, and I found what is the issue.

This PR will add a support for passing a function in config.head configuration for Docs theme.

To support config.head as a function we need to have latest code from core branch for renderComponent metod:

const renderComponent = <T,>(
  ComponentOrNode: React.FC<T> | React.ReactNode,
  props: T,
  functionOnly?: boolean
) => {
  if (!ComponentOrNode) return null
  if (typeof ComponentOrNode === 'function') {
    if (functionOnly) return ComponentOrNode(props)
    return <ComponentOrNode {...props} />
  }
  return ComponentOrNode
}

Note that this is not a function we have in latest tag (v2.0.0-beta.5). The functionOnly is added later.

Important part is we have functionOnly and in case it is true we return ComponentOrNode(props). And that is what will make config.head as a function to be rendered into the Head.

Also we need to do what my PR suggest to call renderComponent with the functionOnly = true, because only in that case we will support both cases for config.head: function and Element.

Example of the config.head as a function we will support after this PR, and releasing new tag.

  head: ({title, meta}) => (
    <>
      <meta name="description" content={meta.description ? meta.description: "Default description"} />
    </>
  ),

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[shuding]

This makes sense, thank you!

[raproid]

@B2o5T @shuding What is the replacement for meta.description in beta 25? The page won't render showing me that it doesn't recognize meta.description in my theme config.

I'm using this example for testing:
head: ({title, meta}) => (
<>
<meta name="description" content={meta.description ? meta.description: "Default description"} />
</>
),

[dimaMachina]

nextra/examples/swr-site/theme.config.tsx

Line 128 in 09b4102

config.frontMatter.description ||