The url of the sitemap should match the actual url

[tam315]

Since gatsby forces the URL to be in lowercase letters, the URL of the site map must also be lowercase.

---

When use gatsby with markdowns, filename may contain UpperCase letter.

On this situation, gatsby-plugin-sitemap generates the url with UpperCase,
and Gatsby generates path with lowercase.

As a result, search engine claims that sitemap's url is not valid.

They say "There is no canonical tag in the URL of the Sitemap"
as they indexes the actual (lowercase) URL and
thinks that the URL of the site map is not canonical.

---

e.g.

Filename:
2018-04-09-AboutJamStack.md

Sitemap URL:
https://www.some.org/2018-04-09-AboutJamStack/ (301 redirected to actual url)

Actual URL:
https://www.some.org/2018-04-09-aboutjamstack/

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[KyleAMathews]

Hmmm I wasn't aware that Gatsby forced URLs to be lowercase? I've built sites with uppercase URLs and it worked fine. Perhaps there's something else going on?

[tam315]

thanks @KyleAMathews

I checked and realized that redirection occurs only in production enviroment (Netlify).
redirection not happens on the localhost,

Also, I noticed that converting to lowercase should be done with my custom onCreateNode,
not in sitemap-plugin.

so, this PR has become useless, I close this. sorry to mess up.

exports.onCreateNode = ({ node, getNode, boundActionCreators }) => {
  const { createNodeField } = boundActionCreators;

  if (node.internal.type === 'MarkdownRemark') {
    const slug = createFilePath({ node, getNode, basePath: '_posts/blog' });

    createNodeField({
      node,
      name: 'slug',
      value: slug.toLowerCase(),
    });
  }
};