Empty Markdown frontmatter at build time

[PaulFarault]

What version of astro are you using?

1.0.6

Are you using an SSR adapter? If so, which one?

None

What package manager are you using?

npm

What operating system are you using?

Linux

Describe the Bug

When creating custom Markdown plugins (as in the doc):

• Frontmatters are empty at build time.
• It seems that Markdown files are processed twice at build time.

The output is correct at the end but the lack of frontmatter makes development harder.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/withastro-astro-vgrdek?file=content%2Farticle1.md,content%2Farticle2.md,astro.config.ts,src%2Fplugins%2FremarkGetTitle.ts,src%2Fpages%2Findex.astro

Participation

• [ ] I am willing to submit a pull request for this issue.