Debug Tuist Project Issue

Quick Start

Ask the user to describe the issue and the project setup (targets, dependencies, configurations, platform).
Confirm the issue exists with the latest release by running mise exec tuist@latest -- tuist generate against a reproduction project.
If confirmed, clone the Tuist repository and build from source to test against main.
Triage: fix the bug and open a PR, advise on misconfiguration, or recommend the user files an issue with a reproduction.

Step 1: Gather Context

Ask the user for:

What command they ran (e.g. tuist generate)
The error message or unexpected behavior
When the issue happens: generation time, compile time, or runtime (app launch or later)
Their project structure: targets, platforms, dependencies (SwiftPM, XCFrameworks, local packages)
Their Project.swift and Tuist.swift content (or relevant excerpts)
Their Tuist version (tuist version)

The answer to "when" determines the verification strategy:

Generation time: the issue might be a Tuist bug or a project misconfiguration. Reproduce with tuist generate.
Compile time: the generated project has incorrect build settings, missing sources, or wrong dependency wiring. Reproduce with xcodebuild build after generation.
Runtime: the app builds but crashes or misbehaves on launch or during use. Reproduce by installing and launching on a simulator.

Step 2: Reproduce with the latest release

Before investigating the source code, confirm the issue is not already fixed in the latest release.

Set up a temporary reproduction project

REPRO_DIR=$(mktemp -d)
cd "$REPRO_DIR"

Create minimal Tuist.swift, Project.swift, and source files that reproduce the user's scenario. Keep it as small as possible while still triggering the issue.

Run generation with the latest Tuist release

mise exec tuist@latest -- tuist generate --no-open --path "$REPRO_DIR"

If the issue involves dependencies, install them first:

mise exec tuist@latest -- tuist install --path "$REPRO_DIR"

Check the result

If generation succeeds and the issue is gone, tell the user to update to the latest version.
If the issue persists, continue to Step 3.

Step 3: Build Tuist from Source

Clone the repository and build the tuist executable and ProjectDescription library from source to test against the latest code on main.

TUIST_SRC=$(mktemp -d)
git clone --depth 1 https://github.com/tuist/tuist.git "$TUIST_SRC"
cd "$TUIST_SRC"
swift build --product tuist --product ProjectDescription --replace-scm-with-registry

The built binary will be at .build/debug/tuist. Use it to test the reproduction project:

"$TUIST_SRC/.build/debug/tuist" generate --no-open --path "$REPRO_DIR"

If the issue is fixed on main

Tell the user the fix is already on main, and it hasn't been released, tell them it'll be in the nest release and point them to the relevant commit if you can identify it.

If the issue persists on main

Continue to Step 4.

Step 4: Triage the Issue

Investigate the Tuist source code to understand why the issue occurs.

Outcome A: It is a bug

Identify the root cause in the source code.
Apply the fix.

Verify by rebuilding and running against the reproduction project:

cd "$TUIST_SRC"
swift build --product tuist --product ProjectDescription --replace-scm-with-registry
"$TUIST_SRC/.build/debug/tuist" generate --no-open --path "$REPRO_DIR"

Zip the reproduction project and include it in the PR:

cd "$REPRO_DIR" && cd ..
zip -r reproduction.zip "$(basename "$REPRO_DIR")" -x '*.xcodeproj/*' -x '*.xcworkspace/*' -x 'Derived/*' -x '.build/*'

Open a PR on the Tuist repository with:
- The fix
- The zipped reproduction project attached or committed as a fixture
- A clear description of the root cause and how to verify the fix

Outcome B: It is a misconfiguration

Tell the user what is wrong and how to fix it. Common misconfigurations:

Missing tuist install before tuist generate when using external dependencies
Incorrect source or resource globs that exclude or double-include files
Mismatched build configurations between the project and external dependencies
Wrong product types for dependencies (static vs dynamic)
Missing -ObjC linker flag for Objective-C dependencies
Using sources and resources globs together with buildableFolders

Provide the corrected manifest snippet so the user can apply the fix directly.

Outcome C: Unclear or needs team input

If you cannot determine whether it is a bug or misconfiguration, recommend the user:

Open a GitHub issue at https://github.com/tuist/tuist/issues with:
- The reproduction project (zipped)
- The error output
- Their Tuist version and environment details

Provide a summary of what you investigated and what you ruled out, so the user does not have to repeat the triage.

Build Verification

When testing a fix, always verify the full cycle:

# Build the patched tuist
cd "$TUIST_SRC"
swift build --product tuist --product ProjectDescription --replace-scm-with-registry

# Install dependencies if needed
"$TUIST_SRC/.build/debug/tuist" install --path "$REPRO_DIR"

# Generate the project
"$TUIST_SRC/.build/debug/tuist" generate --no-open --path "$REPRO_DIR"

# Build the generated project
xcodebuild build \
  -workspace "$REPRO_DIR"/*.xcworkspace \
  -scheme <scheme> \
  -destination "platform=iOS Simulator,name=iPhone 16 Pro"

Runtime Verification

When the user reports a runtime issue (crash on launch, missing resources at runtime, wrong bundle structure, or unexpected behavior), you must go beyond building and actually launch the app on a simulator.

Launch and monitor for crashes

# Boot a simulator
xcrun simctl boot "iPhone 16 Pro" 2>/dev/null || true

# Build for the simulator
xcodebuild build \
  -workspace "$REPRO_DIR"/*.xcworkspace \
  -scheme <scheme> \
  -destination "platform=iOS Simulator,name=iPhone 16 Pro" \
  -derivedDataPath "$REPRO_DIR/DerivedData"

# Install the app
xcrun simctl install booted "$REPRO_DIR/DerivedData/Build/Products/Debug-iphonesimulator/<AppName>.app"

# Launch and monitor — this will print crash info if the app terminates abnormally
xcrun simctl launch --console-pty booted <bundle-identifier>

The --console-pty flag streams the app's stdout/stderr so you can observe logs and crash output directly. Watch for:

Immediate crash on launch: usually a missing framework, wrong bundle ID, missing entitlements, or stripped ObjC categories (-ObjC linker flag missing)
Crash after a few seconds: often missing resources (images, storyboards, XIBs, asset catalogs) or a bundle structure mismatch
Runtime misbehavior without crash: wrong resource paths, missing localization files, or incorrect Info.plist values

Check crash logs

If the app crashes without useful console output, pull the crash log:

# List recent crash logs for the app
find ~/Library/Logs/DiagnosticReports -name "<AppName>*" -newer "$REPRO_DIR" -print

Read the crash log to identify the crashing thread and the faulting symbol.

Done Checklist

Gathered enough context from the user to reproduce the issue
Determined whether the issue is at generation time, compile time, or runtime
Confirmed whether the issue exists in the latest release
Tested against Tuist built from source (main branch)
If runtime issue: launched the app on a simulator and verified the crash or misbehavior
Triaged the issue as a bug, misconfiguration, or unclear
If bug: applied fix, verified it, and opened a PR with reproduction project
If misconfiguration: provided corrected manifest to the user
If unclear: gave the user a summary and recommended next steps

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