1k-patching-native-modules

Original：🇺🇸 English
Translated

Patches native modules (expo-image, react-native, etc.) to fix native crashes or bugs.

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Sourceonekeyhq/app-monorepo
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npx skill4agent add onekeyhq/app-monorepo 1k-patching-native-modules

Tags

Translated version includes tags in frontmatter
mobile-developmentnative-module-patchingcrash-fixpatch-packagereact-native

SKILL.md Content

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Patching Native Modules

Follow this workflow to analyze crash logs, fix native module bugs, and generate patches.

Workflow Overview

1. Analyze Crash Log → 2. Locate Bug → 3. Fix Code → 4. Clean Build Artifacts → 5. Generate Patch → 6. Commit & PR

Step 1: Analyze Crash Log

iOS Crash (EXC_BAD_ACCESS / KERN_INVALID_ADDRESS)

Key information to extract:
  • Exception type: 
    EXC_BAD_ACCESS
    , 
    SIGABRT
    , etc.
  • Stack trace: Identify the crashing function
  • Memory address: Helps identify nil pointer issues
  • Library: Which native module is crashing
Example crash pattern:
EXC_BAD_ACCESS: KERN_INVALID_ADDRESS at 0x3c61c1a3b0d0
 objc_msgSend in unknown file
 -[SDWebImageManager cacheKeyForURL:context:]  ← Crashing function
 -[SDWebImageManager loadImageWithURL:options:context:progress:completed:]

Android Crash (NullPointerException / OOM)

Look for:
  • Exception class: 
    NullPointerException
    , 
    OutOfMemoryError
  • Stack trace: Java/Kotlin method chain
  • Thread info: Main thread vs background

Step 2: Locate the Bug

Find native module source

bash
# iOS (Swift/Objective-C)
ls node_modules/<package>/ios/

# Android (Kotlin/Java)
ls node_modules/<package>/android/src/main/java/

Common crash causes

Crash TypeCommon CauseFix Pattern
EXC_BAD_ACCESS
Nil pointer dereferenceAdd 
guard let
check
KERN_INVALID_ADDRESS
Accessing deallocated memoryUse weak references
NullPointerException
Null object accessAdd null check
OutOfMemoryError
Large image/data processingAdd size limits

Step 3: Fix the Code

iOS (Swift) - Nil Check Pattern

swift
// Before (crashes when uri is nil)
imageManager.loadImage(with: source.uri, ...)

// After (safe)
guard let sourceUri = source.uri, !sourceUri.absoluteString.isEmpty else {
  onError(["error": "Image source URI is nil or empty"])
  return
}
imageManager.loadImage(with: sourceUri, ...)

Android (Kotlin) - Null Check Pattern

kotlin
// Before
val uri = source.uri
loadImage(uri)

// After
val uri = source.uri ?: return
if (uri.toString().isEmpty()) return
loadImage(uri)

Step 4: Clean Build Artifacts (CRITICAL)

Before generating patch, MUST clean Android build cache:
bash
# Remove Android build artifacts to avoid polluting the patch
rm -rf node_modules/<package>/android/build

# For expo-image specifically:
rm -rf node_modules/expo-image/android/build
Why this matters:
  • Android build generates 
    .class
    , 
    .jar
    , binary files
  • These pollute the patch file (can grow to 5000+ lines)
  • patch-package will include these unwanted files

Step 5: Generate Patch

bash
# Generate patch file
npx patch-package <package-name>

# Example:
npx patch-package expo-image
Patch file location: 
patches/<package-name>+<version>.patch

Verify patch content

bash
# Check patch doesn't include unwanted files
grep -c "android/build" patches/<package-name>*.patch
# Should return 0

# View actual changes
head -100 patches/<package-name>*.patch

Step 6: Commit & Create PR

bash
# Stage patch file
git add patches/<package-name>*.patch

# Commit with descriptive message
git commit -m "fix(ios): prevent EXC_BAD_ACCESS crash in <package> when <condition>

Add guard checks in <package> native layer to prevent crash when <scenario>.

Fixes Sentry issue #XXXXX"

# Create PR
gh pr create --title "fix(ios): <description>" --base x

Common Packages & Their Native Locations

PackageiOS SourceAndroid Source
expo-image
node_modules/expo-image/ios/
node_modules/expo-image/android/src/
react-native
node_modules/react-native/React/
node_modules/react-native/ReactAndroid/
@react-native-async-storage/async-storage
node_modules/@react-native-async-storage/async-storage/ios/
...android/src/
react-native-reanimated
node_modules/react-native-reanimated/ios/
...android/src/

Existing Patches Reference

Check existing patches for patterns:
bash
ls patches/
cat patches/expo-image+3.0.10.patch

Troubleshooting

Patch file too large

bash
# Clean all build artifacts
rm -rf node_modules/<package>/android/build
rm -rf node_modules/<package>/ios/build
rm -rf node_modules/<package>/.gradle

# Regenerate
npx patch-package <package>

Patch not applying

bash
# Check package version matches
cat node_modules/<package>/package.json | grep version

# Rename patch if version changed
mv patches/<package>+old.patch patches/<package>+new.patch

Swift/Kotlin syntax help

Swift guard let:
swift
guard let value = optionalValue else {
  return  // Must exit scope
}
// value is now non-optional
Kotlin null check:
kotlin
val value = nullableValue ?: return
// value is now non-null

Related Files

  • Patches directory: 
    patches/
  • expo-image iOS: 
    node_modules/expo-image/ios/ImageView.swift
  • expo-image Android: 
    node_modules/expo-image/android/src/main/java/expo/modules/image/