Reference

Every option the collapse-output extension accepts.

The complete collapse-output configuration: the cell options, the document options, the two rendering methods, and how a summary is chosen.

Enabling the filter

filters:
  - collapse-output

Cell options

Written as Quarto cell options, with the #| prefix.

```{python}
print("Folded, under a summary this cell set for itself.")
```
Click to view results 
Folded, under a summary this cell set for itself.
Cell options.
Option Type Default Description
output-fold boolean false Folds this cell’s output. Set to false to opt out when collapse-all-outputs is on.
output-summary string The summary text for this cell. Overrides both summary-template and summaries.
output-open boolean Whether this cell starts open, overriding default-open.

Document options

extensions:
  collapse-output:
    method: lua
    collapse-all-outputs: false
    default-open: false
    auto-collapse-size: 20
    output-types: stdout, stderr, display
    summary-template: "{type} ({lines} lines)"
    summaries:
      stdout: "Console output"
      stderr: "Warnings and errors"
Document and project options.
Option Type Default Description
method lua or javascript lua Where the folding happens: at render time, or in the browser.
collapse-all-outputs boolean false Folds every cell output, without marking each cell.
default-open boolean false Whether folded output starts open.
auto-collapse-size integer Outputs with at least this many lines are forced closed, whatever default-open says.
output-types string or list all Which kinds of output to fold: stdout, stderr, display, output. A comma-separated string or a YAML list. A name that is not one of the four is dropped with a warning.
summary-template string {type} The summary text, when a cell gives none. Takes {type} and {lines}.
summaries object Summary text per output type, keyed by the names above.
Note

An extensions block in a document’s front matter replaces the project’s extensions block rather than merging into it. A page that sets one option there has to restate the rest, including the configuration of any other extension the project sets.

Output types

Each kind of output Quarto emits carries its own class, and output-types selects among them.

Output types.
Name What it is
stdout Printed results and console text.
stderr Warnings and error messages.
display Rich display output: plots, tables, HTML widgets.
output Any cell output not covered above.

Restricting the list leaves everything else unfolded, which is the usual way to fold noisy warnings while leaving plots visible.

How the summary is chosen

The first of these that applies wins:

  1. The cell’s own output-summary.
  2. The entry in summaries for that output type.
  3. summary-template, with {type} and {lines} filled in.

{lines} counts the lines of the output being folded, so "{type} ({lines} lines)" tells a reader what they are opening. The count is taken from the text of the block, which suits console output; rich display output is one block whatever it draws, so a figure or a table reports a single line, or none when it carries no text. An entry in summaries for a given type replaces the template for that type entirely, so a type you name there never shows a line count.

The two methods

Rendering methods.
Method When it runs Trade-off
lua At render time. The <details> elements are in the file Quarto writes. Works without JavaScript, and the folded state is in the HTML.
javascript In the browser, after the page loads. Adds a script; a reader with JavaScript disabled sees every output unfolded.

A method that is neither of the two is reported as a warning and the render continues with lua. An auto-collapse-size that is not a non-negative integer is reported the same way and ignored.

Precedence

Whether an output is folded at all:

  • output-fold on a cell beats collapse-all-outputs, in both directions.

Whether a fold starts open:

  • auto-collapse-size comes first, and forces a long output closed whatever the rest say.
  • output-open on a cell beats default-open.

Limitations

  • HTML formats only. Elsewhere the output is left alone rather than folded.
  • Folding applies to cell output, not to the source. Quarto’s own code-fold covers the source.
  • output-fold and output-summary are cell options, so they need the #| prefix rather than a chunk attribute.
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