Tree shake icon fonts with 0 icons retained

@gaaclarke

The icon tree shaker skips tree shaking fonts that have 0 IconData const instances:

flutter/packages/flutter_tools/lib/src/build_system/targets/icon_tree_shaker.dart

Lines 288 to 290 in b5971ca

    
           if (!families.contains(familyKey)) { 
        
             continue; 
        
           }

With the migration to @RecordUse() in #190225 the compiler got smarter and figured out more unreachable const instances than const_finder did, leading to some fonts now having 0 IconData instances instead of a small number of const instances.

So, we need to somehow signal to the icon tree shaker that something is an icon font instead of a normal font.

Context: #190225 (comment)

Thanks @gaaclarke for the report! 🙏

FYI @goderbauer @natebiggs @bkonyi

One issue is that the asset declaration in the pubspec.yaml does not specify if a font is an icon font or a normal font.

flutter:
  fonts:
    - family: CupertinoIcons
      fonts:
        - asset: assets/CupertinoIcons.ttf

and

flutter/packages/flutter_tools/lib/src/asset.dart

Lines 113 to 129 in b5971ca

    
           /// The effect of adding `uses-material-design: true` to the pubspec is to insert 
        
           /// the following snippet into the asset manifest: 
        
           /// 
        
           /// ```yaml 
        
           /// material: 
        
           ///   - family: MaterialIcons 
        
           ///     fonts: 
        
           ///       - asset: fonts/MaterialIcons-Regular.otf 
        
           /// ``` 
        
           const kMaterialFonts = <Map<String, Object>>[ 
        
             <String, Object>{ 
        
               'family': 'MaterialIcons', 
        
               'fonts': <Map<String, String>>[ 
        
                 <String, String>{'asset': 'fonts/MaterialIcons-Regular.otf'}, 
        
               ], 
        
             }, 
        
           ];

If we move the icon fonts to DataAssets reported from the hook/build.dart as theorized in #174860 (comment), then we would know in those hooks which fonts are intended to be tree-shaken or not.

We do have @staticIconProvider annotations, which were used by const_finder (but also didn't prevent 0-icon fonts). We could theoretically try to use these to identify the fonts, but it would require a complete extra pass over the codebase.

We cannot do the following unfortunately:

@RecordUse()
class StaticIconProvider {
  final String fontFamily;
}

@StaticIconProvider(CupertinoIcons.iconFont)
abstract final class CupertinoIcons { }

Because @RecordUse() does not record annotations that are not runtime objects in the final program. (dart2js does not represent annotations as const instances.)

A short-term workaround for the two built-in fonts is to hardcode the font names in the icon_tree_shaker.dart. That doesn't work for user-defined icon fonts (but it is probably less likely users transitively depends on a user-defined icon font and not use it all).

[icon_tree_shaker] Tree-shake material and cupertino with 0 icons (fl…

Fixed by #190905.

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.

Navigation Menu

Repository navigation

Tree shake icon fonts with 0 icons retained #190902

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

	/// The effect of adding `uses-material-design: true` to the pubspec is to insert
	/// the following snippet into the asset manifest:
	///
	/// ```yaml
	/// material:
	/// - family: MaterialIcons
	/// fonts:
	/// - asset: fonts/MaterialIcons-Regular.otf
	/// ```
	const kMaterialFonts = <Map<String, Object>>[
	<String, Object>{
	'family': 'MaterialIcons',
	'fonts': <Map<String, String>>[
	<String, String>{'asset': 'fonts/MaterialIcons-Regular.otf'},
	],
	},
	];

Tree shake icon fonts with 0 icons retained #190902

Description

Activity

dcharkes commented on Aug 11, 2026

bkonyi commented on Aug 18, 2026

github-actions commented on Sep 1, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions