Preserve line breaks when copying table cells containing <br> elements

[aradhyacp]

Description

Fixes an issue where copying rendered Markdown tables lost line breaks inside cells containing <br> elements.

Previously, table extraction relied on textContent, which removed <br> elements without preserving them as newline characters. This caused multiline cell content to be merged together when copying tables as Markdown, CSV, or TSV.

This change preserves line breaks during table extraction so copied table content maintains the original formatting.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Refactoring (no functional changes)

Related Issues

Fixes #553
Closes #553
Related to #553

Changes Made

• Replaced textContent based table cell extraction with a recursive text extraction helper.
• Preserved <br> elements by converting them into newline characters during extraction.
• Ensured nested elements containing line breaks are handled correctly.
• Improved copied table output consistency across Markdown, CSV, and TSV formats.
• Added test coverage for single, multiple, and nested <br> elements.

Testing

• All existing tests pass
• Added new tests for the changes
• Manually tested the changes

Test Coverage

Added tests covering:

• Converting a single <br> element into a newline.
• Converting multiple <br> elements into newlines.
• Preserving <br> elements inside nested elements.

Manually tested the copy functionality using a local React app.

How I tested it locally:

I used the following test component to verify table rendering and copying behavior:

import { Streamdown } from "streamdown";
import "streamdown/styles.css";

const App = () => {
  const markdown = `
  | Name | Description |
  | --- | --- |
  | Example | Paragraph one.<br>Paragraph two. |
  | Example | Paragraph one.<br>Paragraph two. |
  | Example | Paragraph one.<br>Paragraph two. |
  | Example | Paragraph one.<br>Paragraph two. |
  | Example | Paragraph one.<br>Paragraph two. |
  `;

  return (
    <div className="App">
      <div className="mx-auto mt-5 w-200">
        <Streamdown>{markdown}</Streamdown>
      </div>
    </div>
  );
};

export default App;

Screenshots/Demos

Before Markdown Copy

After Markdown Copy

Before CSV Copy

After CSV Copy

Before TSV Copy

After TSV Copy

Checklist

• My code follows the project's code style
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have created a changeset (pnpm changeset)

Changeset

• I have created a changeset for these changes

Additional Notes

This change only affects table text extraction behavior. The existing Markdown, CSV, and TSV serializers continue to handle formatting based on the extracted table data.

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