How do I use quarto project for a presentation?

[einarpersson]

Description

I have so far only used quarto for separate files and not as a project. However, as I want to be able to control the output directory I want to use a proper project now (because as I understand it, this is then required).

Here is my _quarto.yml

project:
  title: "My Test Project"
  output-dir: .out

format: revealjs

and I also have a index.qmd

---
format:
  revealjs:
---

## Quarto

Bla bla bla

I expected quarto preview to "just work".

Instead I get this error

❯ quarto preview
Preparing to preview
ERROR: TypeError: Cannot read properties of null (reading 'bibliography')

Stack trace:
    at file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80458:32
    at Array.forEach (<anonymous>)
    at fixupMergeableScalars (file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80457:11)
    at file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80476:17
    at Array.forEach (<anonymous>)
    at fixupFormat (file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80472:33)
    at mergeQuartoConfigs (file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80482:25)
    at resolveFormatsFromMetadata (file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80314:25)
    at async resolveFormats (file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80509:26)
    at async renderContexts (file:///home/einar/opt/quarto-1.6.42/bin/quarto.js:80377:21)

Running quarto preview index.qmd gives the same result.

It looks as if bibliography is a required key, but I haven't used it previously when doing individual files. So is it required for projects but not for individual files? Why? And I don't see anything in the project reference that states that it is required. I don't need/want it.

Additional info

Version 1.6.42
Running Ubuntu 22.04.5 LTS under WSL2

[mcanouil]

Your example is not reproducible and is lacking elements.
The error is pretty clear, you have set bibliography somewhere.
Check your parent directories and/or try in a completely different directory.

To be clear, I cannot reproduce your issue.

Also, you really should read and at least be aware of:

• Output directory in quarto-cli #2171

[einarpersson]

Well, it is valid yaml. But it will be interpreted as null.

Using

format:
  revealjs: {}

makes it work again.

I suppose I was wrong to assume that an empty dict/object would be interpreted the same way. I mostly deal with yaml when doing docker stuff, and there I i remember correctly you can often use something like

networks:
  my_network:

and then add properties as needed

networks:
  my_network:
    name: "my-custom-name"

[mcanouil]

why would it start working if i add a single arbritary option (eg. incremental)? How is that intuitive?

That's not Quarto, that's YAML.

This is invalid YAML

key:

key:
  subkey:

This is valid YAML

key: value

key:
  subkey

key:
  subkey: value

[einarpersson]

1. I pinged you in one reply. I'm sorry if that makes you be pinged in every subsequent reply. I have not pinged you explicitly in more than one message.

2. Go to yamllint.com. Write key:. Press "Go". See result.

Edit: In other words, you are wrong in your statement. It is valid yaml to have a empty key. It corresponds to a null value. Also see my docker example above why this can be useful (as it doesnt force you to change structure of the yaml when going from no options to some options).

yaml

key:

yaml

{
  "key": null
}

[mcanouil]

About the bad error message:

• Missing/null YAML value leads to bad error message #12369

[mcanouil]

1. I pinged you in one reply. I'm sorry if that makes you be pinged in every subsequent reply. I have not pinged you explicitly in more than one message.

Sorry, another user is pinging me several times at the same time as this thread. I misread.

2. Go to yamllint.com. Write key:. Press "Go". See result.

But that's not the issue, revealjs or the other formats does not take null or an empty {}.
It needs proper values. null will be taken as is and that is wrong.

I meant invalid YAML in Quarto/Pandoc YAML schema / context.

If you don't want to set any format specific values and want to set multiple format:

format:
  revealjs: default
  html:
   embed-resources: true

[mcanouil]

TL;DR

Not setting a value or setting it to null means no values, not "default" value.
Set key: default or key to use the default.

[einarpersson]

You:

That's not Quarto, that's YAML.
This is invalid YAML

Also you: (later, after showing you that it valid yaml)

I meant invalid YAML in Quarto/Pandoc YAML schema / context.

It is totally fine that quarto does not interpret null and an empty object in the same way, they are different things! Refering to another tool (docker compose) I showed that it can sometimes be beneficial to treat them the same (i.e. "the user want X but did not specify any more options, therefore apply the default options).

But that's not the issue, revealjs or the other formats does not take null or an empty {}.

That is not true according to my experience here and now.

format:
  revealjs: {}

works as of this writing. Please try it out.

EDIT: copied my currently working _quarto.yml

project:
  output-dir: .out
  render:
    - "*.qmd"
    - "!materials/"
  preview:
    port: 4200

format:
  revealjs: {}

[mcanouil]

So it means Quarto considers an empty value of the same type as the expected one is to be replaced by the default.

Anyhow, revealjs: null is invalid and is showed in IDEs such as VSCode/Positron via the "quarto" extension.

[cderv]

The error message is definitely not not helpful nor the right one. It is happening because it is parsed as null and not an empty object {}. And subsetting from null creates the error.

Odd part is that rendering the document should have fail validation

❯ quarto render index.qmd
ERROR: Validation of YAML front matter failed.
ERROR: (line 3, columns 3--11) Field "revealjs" has empty value but it must instead be an object
2: format:
3:   revealjs: 
             ~
4: ---

ERROR: Render failed due to invalid YAML.

So you should not have seen the issue about bibliography unless YAML validation is bypassed or not working somehow.

Which version of Quarto are you using ?

Anyhow, I see what could go wrong with revealjs: null parsed in YAML. Could be fixup to revealjs: {}. This is what we do when we see a string, and why using default is the usual way when multi format is required.

format: 
  revealjs: default
  html:
    toc: true

But IMO there are much more place than this bibliography field problem, where we do expect an object and not a null value as our schema validates.

[cderv]

now that I try to "break" it again I get a better validation error

This is the expected error. Using null is not valid and so an error is raised, as you are seeing.

When I change the frontmatter in index.qmd (not _quarto.yml!).

This would mean we are not validating for document inside project 🤔 So I checked:

• If you do quarto render, you are seing the YAML validation error
• But if you do quarto preview then you don't see the validation error. (and we hit the problem of fixupMergeableScalars not handling null value correctly).

@cscheid it seems like an issue that we don't validate the same way. Do you see where this could be?

[cderv]

@mcanouil I missed you reply before posting. I don't get same behavior you see. I'll post in the other issue.

[mcanouil]

You don't need to be in a project.
The only thing needed is:

mkdir whatever
cd whatever
echo "---\nformat:\n  revealjs:\n---\n" > index.qmd
quarto render index.qmd # proper error
quarto preview index.qmd # bad error

[cderv]

quarto render index.qmd # proper error
quarto preview index.qmd # bad error

Oh so you do get the same behavior as me. Yes this is the problem. No validation error for preview.

Sorry I missed that you opened an issue for that. Let's continue there

[mcanouil]

Yes, sorry, I was on hurry when I opened the issue to be sure to not forget about it.
I edited and added all the steps to reproduce.
That's a "preview" issue.