feat: make notebook output display limit configurable via

[pandupan]

Description

This PR adds a new setting notebook.output.maxItems that allows users to configure the maximum number of output items rendered per notebook cell.

Problem

The notebook output display limit is hard-coded to 500 output items. When a cell produces more outputs than this limit, a message appears:

"There are more than 500 outputs, show more (open the raw output data in a text editor)"

This affects many real-world use cases:

• ML training loops — printing epoch/loss metrics each iteration
• Data processing pipelines — logging progress for thousands of items
• Debugging with logging — cells mixing print() and logging
• Progress bars (tqdm) — each update creates a new output item

Additionally, the "show more" link often fails with an error (#226261), leaving users with no way to view their truncated output.

Solution

Add a new configurable setting:

"notebook.output.maxItems": 500

Property	Value
Type	number
Default	500 (backward compatible)
Minimum	1
Maximum	10000
Tags	notebookOutputLayout

Implementation

The hard-coded outputDisplayLimit = 500 constant is preserved as a fallback default. Each usage site now reads from the configuration service first:

const outputDisplayLimit = configurationService.getValue<number>(NotebookSetting.outputDisplayLimit) || defaultOutputDisplayLimit;

Files Changed

File	Change
notebookCommon.ts	Add outputDisplayLimit key to NotebookSetting enum
notebook.contribution.ts	Register setting schema with description, type, default, min, max
codeCell.ts	Read limit from IConfigurationService
notebookEditorWidget.ts	Read limit from IConfigurationService
viewportWarmup.ts	Inject IConfigurationService, read limit from config

Testing

1. Open VS Code with a notebook
2. Add "notebook.output.maxItems": 1000 to settings
3. Run a cell that produces >500 outputs:

   for i in range(1000):
       print(f"Iteration {i}")

4. Verify all 1000 outputs are rendered without truncation
5. Verify default behavior (500) still works when setting is not configured

Related Issues

• Fixes Make notebook cell output item limit (500) configurable via setting #325786
• Related: Many output bugs when printing to both STDOUT and STDERR; "There are more than 500 outputs" #228857, ERROR: unable to resolve text model content for notebook cell output #226261, Large text output kills the notebook #110581

---

Note: The npm install step timed out during local testing due to the large repo size. The CI pipeline will handle the full build verification. The changes follow the exact same patterns used by other notebook output settings (e.g., notebook.output.textLineLimit, notebook.output.scrolling).

[Copilot]

Pull request overview

Adds a configurable notebook cell output-rendering limit while preserving the existing default of 500.

Changes:

• Registers notebook.output.maxItems with bounds of 1–10,000.
• Applies the configured limit to cell rendering and output warmup paths.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
notebookCommon.ts	Defines the setting key.
codeCell.ts	Passes the configured limit to output rendering.
notebookEditorWidget.ts	Applies the limit during output warmup.
notebook.contribution.ts	Registers the setting schema.
viewportWarmup.ts	Applies the limit during viewport warmup.

[pandupan]

@microsoft-github-policy-service agree

[pandupan]

Thanks for the review, Copilot!

Comment 1 (integer type): Fixed! Changed type: 'number' to type: 'integer' since output item count must be a whole number.

Comment 2 (construction-time read): Good observation. I followed the same pattern as the existing notebook.output.textLineLimit setting, which is also read at construction time in the same CodeCell constructor and doesn't have a dynamic update subscription. The setting takes effect on newly rendered cells — consistent with how other notebook output settings work. Users can also reload the window to apply to all cells immediately.