Icon preview no longer showing in completion list after Flutter update #6179

Describe the bug

Icon previews (the small rendered glyph shown next to each item in the completion/autocomplete list for Icons.*) stopped appearing after updating Flutter. This was working correctly before the update.

To Reproduce

Steps to reproduce the behavior:

1. Open any .dart file in a Flutter project that imports material.dart.
2. Start typing Icons. inside an Icon() widget (e.g. Icon(Icons.chair).
3. Open the completion list.

Expected behavior

Each icon suggestion in the completion list should show a small rendered preview of the icon glyph next to its name, as it did before updating Flutter.

Actual behavior

The completion list shows only text (icon name + IconData type label) with no rendered icon glyph preview.

Troubleshooting already done

• Confirmed editor.suggest.showIcons is enabled (User and Workspace scopes match).
• Confirmed editor.colorDecorators is enabled, limit 500, default color decorators = auto (no override found in workspace settings).
• Restarted the Dart Analysis Server (Dart: Restart Analysis Server) — completion still works correctly (23 results returned, hover/outline/etc. all functioning), but no icon glyphs render.
• Reloaded the window (Developer: Reload Window).
• Reinstalled the Dart and Flutter extensions from scratch.
• Confirmed no relevant errors in Help > Toggle Developer Tools console when opening the completion list.
• Ran flutter doctor -v — no issues found.
• Confirmed the Dart/Flutter extensions are on the latest published version (3.142.0, 2026-09-01) — changelog contains no icon-related changes.
• Confirmed packages/flutter/lib/src/material/icons.dart in the local Flutter SDK checkout has not changed recently (last modified 2024-12-19), ruling out an icon name/mapping change from the SDK update.

Please complete the following information

Dart Code extension: 3.142.0
Flutter extension: 3.142.0 (activated)

App: Visual Studio Code
App Host: desktop
Version: mac 1.106.2

Workspace type: Flutter (LSP)

Dart (3.13.3): /Users/matrix/development/flutter/bin/cache/dart-sdk
Flutter (3.47.4): /Users/matrix/development/flutter (macOS (darwin/macos))

[✓] Flutter (Channel stable, 3.47.4, on macOS 26.6.2 25G83 darwin-arm64, locale en-EG)
[✓] Android toolchain - develop for Android devices (Android SDK version 36.1.0)
[✓] Xcode - develop for iOS and macOS (Xcode 26.6)
[✓] Chrome - develop for the web
[✓] Connected device (2 available)
[✓] Network resources

• No issues found!

Note: this issue was first noticed on Flutter 3.47.2 / Dart-Code 3.142.0, and is still present after upgrading to Flutter 3.47.4 / Dart 3.13.3 (Dart-Code remains at 3.142.0, the latest available version at time of writing).

Additional context

This started immediately after upgrading the Flutter SDK (previous version unknown/not recorded). No other extensions were changed around the same time. Color decorators for Color(...) constants still work correctly — only the Icons.* glyph previews in completion/hover are affected.

Investigation: icon asset files are present on disk

Following the debugging approach suggested by @DanTup in #3641 (checking that the icon image files are actually present in the installed extension), I checked the locally installed extension folder rather than assuming the images were missing:

$ find ~/.vscode/extensions/dart-code.dart-code-3.142.0 -iname "*icon*" -type d
/Users/matrix/.vscode/extensions/dart-code.dart-code-3.142.0/media/icons
/Users/matrix/.vscode/extensions/dart-code.dart-code-3.142.0/media/doc-icons

media/icons/ only contains editor-UI icon folders (flutter_outline, sidebar, vscode_symbols) — not Flutter Material icon previews.

media/doc-icons/ does contain the actual icon preview assets, and the counts look correct/complete:

$ ls -la ~/.vscode/extensions/dart-code.dart-code-3.142.0/media/doc-icons
drwxr-xr-x@     5 matrix  staff     160 Sep  1 16:04 .
drwxr-xr-x@     7 matrix  staff     224 Sep  1 16:04 ..
-rw-r--r--@     1 matrix  staff     121 Sep  1 16:04 .gitignore
drwxr-xr-x@  2646 matrix  staff   84672 Sep  1 16:04 cupertino
drwxr-xr-x@ 17652 matrix  staff  564864 Sep  1 16:04 material

So the icon image assets themselves are present (this rules out the "missing submodule at publish time" failure mode seen in older issues like #2333). This suggests the regression may instead be in the code that resolves an icon name to its file path under media/doc-icons/material/ (e.g. a folder/naming convention change that the completion/hover renderer isn't matching against), rather than missing assets. I haven't been able to inspect the resolution code myself, but wanted to include this finding so it doesn't need to be re-diagnosed.