feat(appimage): support static appimage runtime

[mmaietta]

Resolves #8686

Summary

This PR adds support for a new AppImage runtime toolset, providing an opt-in alternative to the legacy FUSE2-based AppImage packaging system.

Changes

Configuration Schema Updates

• Added new appimage toolset configuration option in ToolsetConfig
• Supports versions "0.0.0" (legacy) and "1.0.2" (new runtime)
• Default remains "0.0.0" for backward compatibility

New AppImage Building Infrastructure

• New Files:
  • packages/app-builder-lib/src/targets/appimage/appImageUtil.ts - Core AppImage building utilities for the new runtime
  • packages/app-builder-lib/src/targets/appimage/appLauncher.ts - Handles icon copying and MIME type generation
  • packages/app-builder-lib/templates/appimage/AppRun.sh - Template for AppImage launcher script

AppImage Target Refactoring

• Updated AppImageTarget.ts to support both legacy and new toolsets
• Legacy build path (buildFuse2AppImage) preserved when toolset is "0.0.0" or not specified
• New build path uses buildAppImage from appImageUtil.ts for version "1.0.2"
• Both paths generate proper blockmap and update info

Toolset Management

• Added getAppImageTools() function to download and manage AppImage toolset artifacts
• Downloads from electron-userland/electron-builder-binaries releases
• Includes architecture-specific runtimes (x64, ia32, arm32, arm64)
• Bundles mksquashfs, desktop-file-validate, and runtime libraries

Key Features of New Runtime

• Uses static AppImage runtime (FUSE-less)
• Supports multiple compression formats (xz, lzo, zstd)
• Hardlink-based file copying for efficiency with fallback to regular copy
• Generates desktop files, icons, and MIME type associations
• Includes EULA support (text and HTML)
• Proper environment variable setup for Linux desktop integration

Dependency Updates

• Fixed packageMetadata.ts to handle both file: and link: prefixed electron-updater versions for workspace testing

Testing

• Added comprehensive snapshot tests for both AppImage toolset versions
• E2E auto-updater tests for ARM64 and x64 architectures
• Tests for various Windows code signing toolset versions
• All existing tests continue to pass with the legacy toolset

Backward Compatibility

• Default behavior unchanged (uses legacy "0.0.0" toolset)
• Users can opt-in to new runtime by setting toolsets.appimage: "1.0.2" in their build configuration
• Both toolsets produce compatible AppImage outputs with update info

Usage

To use the new AppImage runtime, configure your electron-builder config:

{
  "linux": {
    "target": "AppImage"
  },
  "toolsets": {
    "appimage": "1.0.2"
  }
}

[changeset-bot]

🦋 Changeset detected

Latest commit: 30eccb3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
app-builder-lib	Major
dmg-builder	Major
electron-builder-squirrel-windows	Major
electron-builder	Major
electron-forge-maker-appimage	Major
electron-forge-maker-nsis-web	Major
electron-forge-maker-nsis	Major
electron-forge-maker-snap	Major

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[Copilot]

Pull request overview

Adds an opt-in AppImage toolset that uses a static (FUSE-less) runtime, while keeping the legacy FUSE2-based AppImage build as the default for backward compatibility.

Changes:

• Adds toolsets.appimage ("0.0.0" legacy, "1.0.2" static runtime) to config schema and JSON schema.
• Implements a new AppImage build path (static runtime) alongside the existing legacy AppImage builder path.
• Expands test coverage/snapshots and adjusts CI/docker steps for updater/AppImage-related tests.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
packages/app-builder-lib/src/configuration.ts	Adds toolsets.appimage to the typed configuration.
packages/app-builder-lib/scheme.json	Exposes toolsets.appimage in the generated JSON schema.
packages/app-builder-lib/src/toolsets/linux.ts	Adds downloader/locator for AppImage runtime tool artifacts.
packages/app-builder-lib/src/targets/AppImageTarget.ts	Routes AppImage builds to legacy vs static runtime toolset; adds blockmap append for new path.
packages/app-builder-lib/src/targets/appimage/appImageUtil.ts	Implements static-runtime AppImage assembly (stage dir population + squashfs + runtime prepend).
packages/app-builder-lib/src/targets/appimage/appLauncher.ts	Adds icon copying + MIME type XML generation for the new runtime staging.
packages/app-builder-lib/templates/appimage/AppRun.sh	Adds an AppRun template intended for the new runtime.
packages/app-builder-lib/src/util/packageMetadata.ts	Supports resolving electron-updater version when specified via link: in addition to file:.
test/src/updater/blackboxUpdateTest.ts	Runs updater E2E across multiple winCodeSign and appimage toolset versions; switches test fixture install to pnpm/linking.
test/src/linux/linuxPackagerTest.ts	Restructures AppImage tests to iterate across toolset versions.
test/snapshots/**	Updates/adds snapshots for new suite naming and toolset combinations.
.github/workflows/test.yaml	Builds docker test image before running Linux updater E2E job.
.github/actions/pretest/action.yml	Adjusts Vitest smart cache restore/reset wiring.
package.json	Adjusts test-linux env default and removes some top-level test scripts.
.vscode/launch.json	Adds a pnpm-based debug launch configuration.
.changeset/eight-baths-stick.md	Declares a minor bump for app-builder-lib for the new toolset support.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 5 comments.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 9 comments.

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