Some metadata set in `_metadata.yml` and in YAML header inside document are not correctly merged.

[cderv]

Discussed in #9855

^{Originally posted by McKabue June 3, 2024}

/posts/welcome/index.qmd

---
title: "Welcome To My Blog"
date: "2024-05-01"
categories: [news]
author: "martin from welcome"
---

This is the first post in a Quarto blog. Welcome!

![](thumbnail.jpg)

Since this post doesn't specify an explicit `image`, the first image in the post will be used in the listing page of posts.

/posts/_metadata.yml

categories: [tech]
author:
  - name: James from posts

With the above setup, I get the following post and listing:

---

However, if:

/posts/welcome/index.qmd

---
title: "Welcome To My Blog"
date: "2024-05-01"
---

This is the first post in a Quarto blog. Welcome!

![](thumbnail.jpg)

Since this post doesn't specify an explicit `image`, the first image in the post will be used in the listing page of posts.

/posts/welcome/_metadata.yml

categories: [news]
author: "martin from welcome"

/posts/_metadata.yml

categories: [tech]
author:
  - name: James from posts

I get the following post and listing:

---

When the metadata is in the document file, it overwrites all parent metadata such as authors and categories instead of extending it in the post page.

[cderv]

I looked quickly into this to diagnose and I think this happens also in regular rendering not only for blog or listing.

Basically, we have a part in our code where we "override" any processing that could have been done, by forcing the use of the metadata inside the document.

quarto-cli/src/command/render/pandoc.ts

Lines 978 to 1002 in b34b24d

	// selectively overwrite some resolved metadata (e.g. ensure that metadata
	// computed from inline r expressions gets included @ the bottom).
	const pandocMetadata = ld.cloneDeep(options.format.metadata || {});
	for (const key of Object.keys(engineMetadata)) {
	const isChapterTitle = key === kTitle && projectIsBook(options.project);
	if (!isQuartoMetadata(key) && !isChapterTitle && !isIncludeMetadata(key)) {
	// if it's standard pandoc metadata and NOT contained in a format specific
	// override then use the engine metadata value
	// don't do if they've overridden the value in a format
	const formats = engineMetadata[kMetadataFormat] as Metadata;
	if (ld.isObject(formats) && metadataGetDeep(formats, key).length > 0) {
	continue;
	}
	// don't process some format specific metadata that may have been processed already
	// - theme is handled specifically already for revealjs with a metadata override and should not be overridden by user input
	if (key === kTheme && isRevealjsOutput(options.format.pandoc)) {
	continue;
	}
	// perform the override
	pandocMetadata[key] = engineMetadata[key];
	}
	}

So basically in here:

• pandocMetadata['author'] has correctly the merged authors so the two value
• But author key is not identified as a quarto metadata and so it gets overriden by engineMetadata['author']; which is the document value set.

We got already bitten by this in revealjs for themes, where I added an escape

quarto-cli/src/command/render/pandoc.ts

Lines 994 to 998 in b34b24d

	// don't process some format specific metadata that may have been processed already
	// - theme is handled specifically already for revealjs with a metadata override and should not be overridden by user input
	if (key === kTheme && isRevealjsOutput(options.format.pandoc)) {
	continue;
	}

This is very old codebase (341cc3b from 3 years) for backward compatibility for inline yaml rendering.

So I think either we keep it but we probably need to consider author as a isQuartoMetadata key because we process it. Or we should remove this overwrite which does not make sense anymore probably.

[mcanouil]

FYI:

• How to manage author template, default author and custom authors posts? #8860

it was another issue were all were merged resulting in duplicates, the fix was: 478b3df

[cderv]

Yes this is different. #8860 is really about listing. As I said here, the problem happening also with default project, using shared metadata.

[cderv]

A note that this is not only for author, but any key that will pass the check !isQuartoMetadata(key) && !isChapterTitle && !isIncludeMetadata(key)