primefaces/primeng

ToggleButton does not allow `undefined` as size

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#19591 opened on May 21, 2026

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Type: Buggood first issue

Description

Describe the bug

Most components that have a [size] input allow it to be undefined, which would be the normal size. However, the ToggleButton only allows "small" or "large" as values but not undefined. (https://primeng.org/togglebutton#api.togglebutton.props.size). Note that using null does also not work.
This makes it hard to set it programatically.

Pull Request Link

https://github.com/primefaces/primeng/pull/19592

Reproducer

https://primeng.org/togglebutton#api.togglebutton.props.size

Environment

PrimeNG 21, Angular 21

Angular version

21.0.0

PrimeNG version

v21

Browser(s)

Firefox, CHrome

Steps to reproduce the behavior

  1. Create a <p-togglebutton> component and try to set the [size]="undefined". It will give a build error.

Expected behavior

ToggleButton should also allow undefined as size like other components (e.g., AutoComplete, Select, InputText, etc.)

Contributor guide

Tech stack
angulartypescript
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
1
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic AngularTypeScript types
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
85
Research direction
The issue reports that the ToggleButton component's `size` input does not accept `undefined`, unlike other similar components. A linked PR (https://github.com/primefaces/primeng/pull/19592) may already address this. If not, the fix involves updating the type definition of the `size` property in the ToggleButton component to accept `undefined` as a valid value, likely in the component's TypeScript file (e.g., `togglebutton.ts`). Ensure consistency with other components like AutoComplete or Select.