Feature: Option to remove `| undefined` from optional prop types

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
58/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Active
Tech stack
typescript
Domain
documentation, tooling

Research direction

Start by locating the TypeScript parser entry point and its parser-option handling; no file or test is named in the issue. Compare the requested option with the linked react-docgen-typescript prior art, then verify that enabled parsing removes | undefined from optional prop types while preserving the meaningful type instead of reporting union.

Written by the indexing model from the issue text.

Description

Problem

When using TypeScript's explicit optional property pattern (prop?: Type | undefined), react-docgen displays the type as union instead of showing the actual type.

This pattern is common in codebases using exactOptionalPropertyTypes: true in tsconfig, which requires explicit | undefined for optional properties.

Example
interface ButtonProps {
  onClick?: ((event: MouseEvent) => void) | undefined
  variant?: 'primary' | 'secondary' | undefined
  icon?: ReactNode | undefined
}

In Storybook's props table (using react-docgen), these all display as "union" instead of:

  • (event: MouseEvent) => void
  • 'primary' | 'secondary'
  • ReactNode

Requested Feature

Add a parser option similar to react-docgen-typescript's shouldRemoveUndefinedFromOptional:

{
  shouldRemoveUndefinedFromOptional: true
}

When enabled, this would:

  1. Detect optional properties (those ending with ?)
  2. Strip | undefined from their type representation
  3. Display the actual meaningful type instead of "union"

Prior Art

react-docgen-typescript has this feature via the shouldRemoveUndefinedFromOptional option:
https://github.com/styleguidist/react-docgen-typescript#parseroptions

Workaround

Currently, Storybook users must manually specify table.type.summary for every affected prop:

argTypes: {
  onClick: {
    table: { type: { summary: '(event: MouseEvent) => void' } }
  }
}

This is tedious and error-prone for large component libraries.

Environment

  • react-docgen: latest
  • TypeScript: 7.x with exactOptionalPropertyTypes: true
  • Storybook: 10.x using reactDocgen: 'react-docgen'
Dominant language
TypeScript
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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