Eleventy grey-matter engine not registered error

Posted: May 17, 2023 | Categories: Eleventy

I use a npm package I created called Eleventy-New-Post to create new posts for my Eleventy sites. It saves me the work of copying a post file in the project folder then emptying it before adding the new content for the post. It also automates selecting a category for the post from an automatically generated list of all categories used by the site.

I ran it this morning to generate a new post for a site and after generating the new post file, I fired up the eleventy --serve command to validate something about the post URL when I got this error:

[11ty] Problem writing Eleventy templates: (more in DEBUG output)
[11ty] 1. Having trouble reading front matter from template ./src/posts/2023/joomla-to-eleventy-migration---part-1.md (via TemplateContentFrontMatterError)
[11ty] 2. gray-matter engine "tags: post" is not registered (via Error)
[11ty] Original error stack trace: Error: gray-matter engine "tags: post" is not registered
[11ty] at module.exports (C:\Users\john\AppData\Roaming\npm\node_modules\@11ty\eleventy\node_modules\gray-matter\lib\engine.js:6:11)
[11ty] at module.exports (C:\Users\john\AppData\Roaming\npm\node_modules\@11ty\eleventy\node_modules\gray-matter\lib\parse.js:8:18)
[11ty] at parseMatter (C:\Users\john\AppData\Roaming\npm\node_modules\@11ty\eleventy\node_modules\gray-matter\index.js:109:17)
[11ty] at matter (C:\Users\john\AppData\Roaming\npm\node_modules\@11ty\eleventy\node_modules\gray-matter\index.js:50:10)
[11ty] at C:\Users\john\AppData\Roaming\npm\node_modules\@11ty\eleventy\src\TemplateContent.js:167:20
[11ty] Benchmark 837ms 40% 1× (Data) `./src/_data/popularArticles.js`
[11ty] Copied 189 files / Wrote 0 files in 1.15 seconds (v2.0.1)

The error tells me that the tags front matter property caused the problem, but really happened is I asked Eleventy to generate a site using an empty post. As soon as I added content to the post, the error went away.

The error likely reflects the last property in the YAML front matter for the post.

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