[build-tools] Add iOS Simulator recorder

[sjchmiela]

Why

Add a small Swift helper for recording iOS Simulator screen output from EAS build workers. The helper produces either segmented fMP4 output with manifest metadata for playlist construction or one continuous MP4 when segmentation is disabled.

How

• Added a record-sim Swift package under @expo/build-tools resources.
• Added yarn workspace @expo/build-tools build:record-sim for local builds into packages/build-tools/bin/record-sim.
• Updated iOS worker packaging to build record-sim from source and copy only the executable into the worker archive.
• Ignored the generated local bin/record-sim binary.

Test Plan

• yarn workspace @expo/build-tools build:record-sim
• packages/build-tools/bin/record-sim --help
• bash -n packages/worker/package.sh
• yarn workspace @expo/build-tools typecheck
• ./node_modules/.bin/oxfmt --check packages/build-tools/.gitignore packages/build-tools/package.json packages/worker/package.sh packages/build-tools/src/index.ts

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.28%. Comparing base (a848411) to head (a5e5333).

Additional details and impacted files

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##             main    #3950   +/-   ##
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  Coverage   59.28%   59.28%           
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  Files         935      935           
  Lines       41093    41093           
  Branches     8660     8660           
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  Hits        24356    24356           
  Misses      16643    16643           
  Partials       94       94           

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[Copilot]

Pull request overview

This PR adds a new Swift-based record-sim helper under @expo/build-tools to record iOS Simulator screen output (either segmented fMP4 + manifest metadata for HLS/CMAF-style workflows, or a single MP4 when segmentation is disabled), and updates worker packaging to build and include the executable in iOS worker archives.

Changes:

• Introduces a Swift Package (packages/build-tools/resources/record-sim) implementing a simulator framebuffer-based recorder plus a small CLI.
• Adds a local build script (yarn workspace @expo/build-tools build:record-sim) that builds the Swift executable into packages/build-tools/bin/record-sim.
• Updates iOS worker packaging to build record-sim from source during packaging and include only the executable in the iOS worker tarball; ignores the locally generated binary in git.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/worker/package.sh	Builds record-sim during iOS worker packaging and copies the executable into the worker archive.
packages/build-tools/package.json	Adds build:record-sim script to build/copy the Swift executable into bin/.
packages/build-tools/.gitignore	Ignores the generated bin/record-sim binary.
packages/build-tools/resources/record-sim/Package.swift	Defines the Swift package (library + executable) and required frameworks.
packages/build-tools/resources/record-sim/README.md	Documents output format and CLI/library usage.
packages/build-tools/resources/record-sim/.gitignore	Ignores local SwiftPM/Xcode build outputs.
packages/build-tools/resources/record-sim/Sources/RecordSim/SimulatorRecorder.swift	Implements the recording pipeline using private simulator framebuffer callbacks + AVAssetWriter.
packages/build-tools/resources/record-sim/Sources/RecordSim/RecordingOutputWriter.swift	Handles segmented output emission and writes session.json manifest.
packages/build-tools/resources/record-sim/Sources/RecordSim/FramebufferDisplaySource.swift	Interfaces with private simulator services to obtain IOSurface snapshots and callbacks.
packages/build-tools/resources/record-sim/Sources/RecordSim/PrivateSimulatorServices.swift	Loads private frameworks and locates simulator devices/state.
packages/build-tools/resources/record-sim/Sources/RecordSim/RecordingModels.swift	Defines configuration and manifest/segment model types.
packages/build-tools/resources/record-sim/Sources/RecordSim/Utilities.swift	Shared helpers (time conversion, JSON encoding, monotonic clock).
packages/build-tools/resources/record-sim/Sources/record-sim/main.swift	CLI argument parsing and orchestration of the recorder lifecycle.

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[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

[github-actions]

Subscribed to pull request

File Patterns	Mentions
**/*	@douglowder

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[szdziedzic]

files includes bin/, but prepack neither builds nor prunes bin/record-sim, and the
binary is gitignored. npm-packlist normally excludes untracked gitignored files even
inside a files directory, and nothing consumes the binary from npm today (the worker
builds it from source in package.sh) — so this is a future-trap rather than a live bug:
whether a publisher's stale local arm64 binary sneaks into the tarball depends on npm
ignore-precedence and machine state. Worth making deliberate: either build it in
prepack or exclude it explicitly (e.g. !bin/record-sim in files / .npmignore).

[sjchmiela]

We expect the current setup to work on EAS: the worker packaging path builds record-sim from source for the iOS VM tarball, and @expo/build-tools knowingly does not ship bin/record-sim in the npm package. If private API/Xcode drift turns this into a real compatibility problem, we will change how record-sim gets onto the VM, most likely by building it while the worker is running on that image instead of treating it as a prebuilt package artifact.

[github-actions]

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