storybookjs/storybook

[Bug]: Null can't show as a type with React/Vite/Typescript

Open

#32106 opened on Jul 22, 2025

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 (1 comment) (3 reactions) (1 assignee)TypeScript (89,909 stars) (10,058 forks)batch import
argtypesbughelp wanted

Description

Describe the bug

I expect to see string, null, and number as valid options but null is always removed. I've toggled every option I can find documentation for, but have not figured out how to get null to show.

Reproduction link

https://stackblitz.com/edit/github-fdkzfbvz?file=src%2Fstories%2FButton.tsx

Reproduction steps

  1. Go to above link
  2. See that it looks like screenshot above

System

Storybook Environment Info:

  System:
    OS: Windows 11 10.0.22621
    CPU: (24) x64 12th Gen Intel(R) Core(TM) i7-12850HX
  Binaries:
    Node: 22.16.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.9.2 - C:\Program Files\nodejs\npm.CMD <----- active
  Browsers:
    Edge: Chromium (136.0.3240.92)
  npmPackages:
    @storybook/addon-docs: ^9.0.18 => 9.0.18
    @storybook/addon-onboarding: ^9.0.18 => 9.0.18
    @storybook/react-vite: ^9.0.18 => 9.0.18
    eslint-plugin-storybook: ^9.0.18 => 9.0.18
    storybook: ^9.0.18 => 9.0.18

Additional context

No response

Contributor guide

Tech stack
typescriptreactvite
Domain
frontenddocumentation
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TypeScriptReactStorybook basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the type rendering logic in `@storybook/addon docs`, particularly how union types are handled. The issue occurs when null is part of a union type but gets removed. Look at the source code for the TypeScript docgen plugin (likely in `@storybook/addon docs/src/tsdocgen`) to find where null is filtered out. The reproduction link provides a minimal Stackblitz example. Check if there is a configuration option to preserve null or if it's a bug in the type analysis.