If the goal is a double application, there's probably a better solution.

Remember that:

• The user might use baseUrl /blog/
• The user might put files in /static/blog/
• An author image hosted at /blog/blog/authorImage.png is perfectly valid

I think I'd prefer to not have this extra condition

In the past (useBaseUrl hook) it has been annoying because some users will use baseUrl /docs/ or /blog/ and duplicate paths like /docs/docs/someImage.png or /blog/blog/someImage.png should be allowed

I'd like to have a unit test ensuring that we actually allow /baseUrl/baseUrl/img/ozaki.jpg

What we want is to not apply the baseUrl if the author is a global author (ie it has a key).

My suggestion:

  function toAuthor(frontMatterAuthor: BlogPostFrontMatterAuthor): Author {
    const author = {
      // Author def from authorsMap can be locally overridden by front matter
      ...getAuthorsMapAuthor(frontMatterAuthor.key),
      ...frontMatterAuthor,
    };

    return {
      ...author,
      key: author.key ?? null,
      page: author.page ?? null,
      // global author images have already been normalized
      imageURL: author.key ? author.imageURL : normalizeImageUrl({imageURL: author.imageURL, baseUrl}),
    };
  }

The unit tests should clearly cover this case

I'd like to have a unit test ensuring that we actually allow /baseUrl/baseUrl/img/ozaki.jpg

I don't think that's a good idea. No one should be producing these URLs on purpose. See my opinion in #6294 too.

If a URL is /image.png, it should be come /baseURL/image.png, but /baseURL/image.png should stay that way.

@Josh-Cena it's important that urls are portable, and that we can later use React Router built-in basename which will not have this deduplication logic (although it won't apply to images but only links)

You'll see for yourself that existing sites have /docs/docs already, whether it makes sense to you or not: https://eclipse-muto.github.io/docs/docs/muto

I know you want devs to be explicit in this case and write links such as /docs/docs/muto, but this means this link is not "baseUrl" portable anymore.

Another case: the same sites at Meta are deployed in different fashions for public/internal usage, with/without baseUrl.

I'd like to discourage the usage of links that include the baseUrl to maximize portability.