Rehype to render hashtag as url

Trying to make a something like #tag render as a URL the markdown editor MDEditor using rehypeRewrite. Here's what I have so far

const REG = /\B(\#[a-zA-Z]+\b)(?!;)/gi;

<MDEditor 
    style={{width: "100%", height: "100%"}} 
    minHeight={500} 
    value={value} 
    onChange={(event) => {
        setValue(event || '');
    }} 
    previewOptions={{
        rehypePlugins: [
            [
            rehypeRewrite,
            {
                rewrite: (node : any, index: any, parent: any) => {
                if (node.type === "element" && node.tagName === "p") {
                    let text = getCodeString(node.children);
                    if (REG.test(text)) {
                        node.children = [
                        {
                            type: 'link',
                            url: 'https://example.com',
                            children: [{type: 'text', value: text} ]
                        }];
                    }
                }}
            },
        ]],
    }}
/>

The regex properly matches the text but instead of the node being replaced with a link, it just doesn't render anything.

Any guidance on what I may be doing wrong would be much appreciated

The regex you provided seems correct, the mistake here is how you make the link element. Instead of type link, you should still use type element, and for a link, you need to add additional tags, such as tagName: "a" and properties: {href: 'https://example.com'}.

Basically you can replace the node.children code with this:

                      node.children = [
                        {
                          type: "element",
                          tagName: "a",
                          properties: {
                            href: "https://example.com",
                          },
                          children: [{ type: "text", value: text }],
                        },
                      ];