feat: add size option to DmgOptions for explicit DMG filesystem size

[BarakXYZ]

Summary

Add size option to DmgOptions to allow specifying the DMG filesystem size explicitly. This fixes "No space left on device" errors when building DMGs for large applications (>2GB) or applications with sparse files.

The size option accepts the same syntax as hdiutil's -size argument (e.g., "150m", "4g"). If not specified, the size is calculated automatically (existing behavior).

Changes

• Added size property to DmgOptions interface in macOptions.ts
• Added size to JSON schema validation in scheme.json
• Added size to DmgBuildConfig interface in dmg.ts
• Pass size through to dmgbuild settings in dmgUtil.ts
• Added test for the new option

Usage

dmg: {
  size: "4g", // Explicit 4GB filesystem size
}

Dependency

This PR requires a corresponding change in dmgbuild to read the size option from JSON configuration files:

• dmgbuild PR: Support size option in JSON configuration files dmgbuild/dmgbuild#279

Once the dmgbuild PR is merged and electron-builder-binaries updates its bundled dmgbuild, this feature will be fully functional.

Fixes #8223

[changeset-bot]

🦋 Changeset detected

Latest commit: bbe61d3

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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[mmaietta]

Thanks for opening a PR! Can you please also run pnpm generate-changeset so this is picked up by the CD pipeline?

[BarakXYZ]

Thanks for the review! I've made the following updates:

1. Added changeset as requested.

2. Added shrink option and enhanced the test

To properly verify that the explicit filesystem size is retained in the final DMG, I needed to add a shrink option. Here's why:

By default, dmgbuild runs hdiutil resize -sectors min after populating the image, which shrinks the filesystem to the minimum size regardless of what size was specified. The size option still works correctly in this case - it ensures enough space during the build phase - but the final filesystem ends up at minimum size.

To test that the filesystem actually retains a specific size (e.g., 500MB), we need to disable this shrinking behavior. So I created a follow-up PR to dmgbuild:

• dmgbuild PR Added basic badges. #280: Add shrink option to preserve explicit filesystem size dmgbuild/dmgbuild#280

The shrink option (defaults to true) is independent and additive - users can use size alone, shrink alone, or both together depending on their needs.

The test now uses size: "500m" with shrink: false and verifies the mounted filesystem is in the expected range (450-600MB).

Let me know if you'd like any adjustments!

[mmaietta]

Nicely done! I really like this.

Next steps is to open a PR to pull in latest dmgbuild into our portable/closed-loop toolsets is to update the commit hash here to latest
https://github.com/electron-userland/electron-builder-binaries/blob/5fde804b8911fb43e8a9b41fcc668125c25cd6ec/packages/dmg-builder/build.sh#L8
After that PR is merged + deployed, we can simply bump the toolset versions in

electron-builder/packages/dmg-builder/src/dmgUtil.ts

Lines 27 to 28 in e394e0c

	"dmgbuild-bundle-arm64-9614277.tar.gz": "28e11550cf990f78180a2d82090f35a24588beda3d9165098837714f90ee47ce",
	"dmgbuild-bundle-x86_64-9614277.tar.gz": "4dbf1cc186af62921f8b6f4a5956b28d8622d211797a8b05eb75a260ee9c3fdb",

It's a few-but-simple hoops to jump through ever since I recently got that build pipeline set up. :D

[BarakXYZ]

Thanks for the feedback! Updated the size description to clarify it refers to the initial filesystem size.

Also created the PR to update dmgbuild in electron-builder-binaries:

• feat: update dmgbuild to include size and shrink options electron-builder-binaries#135

Once that's merged and deployed with new binaries, I'll bump the releaseVersion and checksums in dmgUtil.ts.

[mmaietta]

Boomshakalaka
dmg-builder@1.2.0
digest256 are the hashes you want to use

[BarakXYZ]

pewpewpew! Bumped to dmg-builder@1.2.0 with the new checksums. Thank you!!