lerp of ChipThemeData.side is wrong when b is null

Steps to reproduce

The lerp method of ChipThemeData for side doesn't work well when b is null.

Expected results

I expect the transistion to be smooth

Actual results

There is a back and forth in the transition

Code sample

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  BorderSide? _side;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(chipTheme: ChipThemeData(side: _side)),
      home: Scaffold(
        body: Center(
          child: ActionChip(
            label: Text('Chip'),
            onPressed: () {
              setState(() {
                if (_side == null) {
                  _side = BorderSide(width: 5, color: Colors.red);
                } else {
                  _side = null;
                }
              });
            },
          ),
        ),
      ),
    );
  }
}

Screenshots or Video

Screenshots / Video demonstration

Screen.Recording.2025-08-02.at.6.36.40.PM.mov

Thanks for the report and potential fix.

Fix `ChipThemeData` lerp for `BorderSide` (#173160)

Fix `ChipThemeData` lerp for `BorderSide` (flutter#173160)

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

Fix `ChipThemeData` lerp for `BorderSide` (flutter#173160)

Fix `ChipThemeData` lerp for `BorderSide` (#173160)

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`lerp` of `ChipThemeData.side` is wrong when `b` is `null` #173161

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lerp of ChipThemeData.side is wrong when b is null #173161

Description

Steps to reproduce

Expected results

Actual results

Code sample

Screenshots or Video

Activity

darshankawar commented on Aug 4, 2025

github-actions commented on Aug 28, 2025

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Issue actions

`lerp` of `ChipThemeData.side` is wrong when `b` is `null` #173161