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2019 DevDay
Growing LINE for iOS
> Christopher Rogers
> LINE App Dev Team4 Senior Software Engineer
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Lines of Code
400,000
800,000
1,200,000
1,600,000
1.0.0
1.2.0
1.3.0
1.3.4
1.6.1
2.0.2
2.3.1
3.1.0
3.2.1
3.5.0
3.6.5
3.8.2
3.9.3
4.0.1
4.3.1
4.5.0
4.7.1
4.9.1
5.0.2
5.2.1
5.4.0
5.8.0
5.10.0
6.1.1
6.4.0
6.6.1
6.8.5
6.9.2
7.1.2
7.3.0
7.5.0
7.8.0
7.12.0
7.15.0
8.0.0
8.2.1
8.4.1
8.6.0
8.9.0
8.12.1
8.16.1
8.19.0
9.0.2
9.5.0
9.7.1
9.15.1
9.18.0
Objective C Swift
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Agenda
> Dependencies
> Launch Time
> Bridging Objective-C & Swift
> Xcode Project Size
> Build Times
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Dependencies
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Emerging Problems
> Linker settings
> Library updates
> Search paths
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Ƃ
CocoaPods
> Builds/cleans alongside project
> Integrates well with Xcode
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Swift
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Ƃ
Carthage
> Pre-builds frameworks
> No integration with Xcode
> Little to no configuration
> Two dependency managers…
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Hard Problems in Computer Science
Caching With Carthage
> Remote build artifact caching with Rome
> Cache poisoning
> Local caches often broke
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Launch Time
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Dynamic Frameworks
> Solution: make them static frameworks!
> Downsides to static frameworks
• Cannot bundle resources
• Code reuse between executables results in increased binary size
> Dynamic linking (usually) happens on launch
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How To Create
> Create dynamic framework
> Mach-O type: Static Library
> Do not embed
> Resources
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Ƃ
Mixing It Up
> Public headers become part of
module alongside Swift
> Enable Clang modules if needed
• CLANG_ENABLE_MODULES
• DEFINES_MODULE
• PRODUCT_MODULE_NAME
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Ƃ
Public Headers
> “Headers” Build Phase
> File Inspector > Target
Membership
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Module Maps
> MODULEMAP_FILE
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Module Maps
> MODULEMAP_FILE
> umbrella makes directory
contents part of module
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Module Maps
> MODULEMAP_FILE
> umbrella makes directory
contents part of module
> export controls if imported
modules are implicitly imported
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Launch Time
0 ms
2,000 ms
4,000 ms
6,000 ms
8,000 ms
10,000 ms
8.4.0 8.5.0
20%ile 50%ile mean 80%ile
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Bridging Objective-C & Swift
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MyObjCSwiftClass+CategoryName.h
Objective-C Categories
@class MyObjCSwiftClass;
@interface MyObjCSwiftClass
(CategoryName)
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MyObjCSwiftClass+CategoryName.h
Objective-C Categories
// import generated header, which contains MyObjCSwiftClass
#import "LINE-Swift.h"
@interface MyObjCSwiftClass (CategoryName)
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Bridging Objective-C Categories on Swift Types To Swift
> Circular dependency
• Generated header (MyApp-Swift.h)
• Bridging header (MyApp-Bridging-Header.h)
Problematic Code
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> @objc(MyObjCSwiftClass) class MySwiftClass { }
> @class MyObjCSwiftClass; can fail to bridge back to MySwiftClass (rare)
> My fix (#27682) should land in Swift 5.2
Bridging Swift Classes Back To Swift via Objective-C
Bridging Objective-C Categories on Swift Types To Swift
> Circular dependency
• Generated header (MyApp-Swift.h)
• Bridging header (MyApp-Bridging-Header.h)
Problematic Code
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Module Map Workaround
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LINE.modulemap
Module Map Settings
module LINE {
header "LINE-Partial-Swift.h"
}
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Build Settings
Module Map Settings
SWIFT_INCLUDE_PATHS = “$(PROJECT_DIR)/LINE/PartialModule"
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MyObjCSwiftClass+CategoryName.h
Importing in Header
// import generated header, which contains MyObjCSwiftClass
#import "LINE-Swift.h"
@interface MyObjCSwiftClass (CategoryName)
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MyObjCSwiftClass+CategoryName.h
Importing in Header
#ifdef __swift__
@import LINE;
#else
// import generated header, which contains MyObjCSwiftClass
#import "LINE-Swift.h"
#endif
@interface MyObjCSwiftClass (CategoryName)
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Keeping in Sync
{
"MessageViewController.swift": [“MessageViewController”],
"ShareActivity.swift": ["ShareActivity"],
}
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Xcode Project Size
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Merge Conflicts
> Requires understanding Xcode’s project file format
Xcode Project Size
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> Was this a part of the target template?
> Why was this setting needed?
Understanding What Has Been Configured
Merge Conflicts
> Requires understanding Xcode’s project file format
Xcode Project Size
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> Was this a part of the target template?
> Why was this setting needed?
Understanding What Has Been Configured
Slow
> Modifying anything was painfully slow
Merge Conflicts
> Requires understanding Xcode’s project file format
Xcode Project Size
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XcodeGen
> YAML config file
> Can write comments
> Less conflicts
> 88k lines of Xcode configuration
are now ~1,200 lines of YAML.
> Can’t use Xcode to edit project
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Build Times
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> Xcode sometimes decides to rebuild everything
> Incremental builds in Swift sometimes too coarse grained
Tooling Problems
CocoaPods
> Unnecessarily rebuilt after cleaning
Generated Header (LINE-Swift.h)
> Nearly a clean build when modified
Problem Areas
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Precompiling Generated Header
> Mileage may vary
> Usually not necessary nor recommended
Quick Improvements
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> Extended type gets marked dirty when extension modified
> Files marked dirty will propagate dirty flag to all of its extensions
> OTHER_SWIFT_FLAGS = -driver-show-incremental
Limiting Access to Swift Extensions
Precompiling Generated Header
> Mileage may vary
> Usually not necessary nor recommended
Quick Improvements
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And Incremental Compilation
Swift Extensions
class MyClass {
func foo() {
IndexSet().bar()
}
}
extension IndexSet {
func bar() {}
}
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And Incremental Compilation
Swift Extensions
class MyClass {
func foo() {
IndexSet().bar()
}
}
extension IndexSet {
fileprivate func bar() {}
}
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And Incremental Compilation
Swift Extensions
class MyClass {
func foo() {
IndexSet().bar()
}
}
extension IndexSet {
func bar() {}
}
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> Including dependencies managed by CocoaPods & Carthage
Build & Cache Modules With Bazel
Split Up Codebase Into Modules
> Currently 224 modules
> Categorize modules
Long-Term Approach
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> Specific category for extension-safe modules
Code Size for App Extensions
Understanding Dependency Graph
> What is OK to import?
> Where to put new code?
Module Categories
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> Restriction: Cannot import feature-private modules
> Small, focused
> Includes feature-public modules
Others
Module Naming Convention
> Module categories have set prefixes and/or suffixes
Feature-Private (Feature)
> Restriction: Cannot import other features’ private modules
> Example features: Messaging, Timeline, Calls, Pay
Module Categories
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ImportLint
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Benefits of Bazel
Remote
Caching
Reproducible
Fast
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> Reading Package.swift for build settings
Build Code From SwiftPM in Bazel
Replace CocoaPods & Carthage With SwiftPM for Dependency Resolution
> Using swift package resolve
Building With Bazel
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Replace CocoaPods & Carthage With SwiftPM for Dependency Resolution
> Done, but removed SwiftPM due to reliability issues (mostly with CI builds) (SR-10718)
> Now Bazel is downloading hard-coded dependencies
Current Status
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> Manually created Bazel BUILD files for all dependencies
Build Code From SwiftPM in Bazel
Replace CocoaPods & Carthage With SwiftPM for Dependency Resolution
> Done, but removed SwiftPM due to reliability issues (mostly with CI builds) (SR-10718)
> Now Bazel is downloading hard-coded dependencies
Current Status
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> Manually created Bazel BUILD files for all dependencies
Build Code From SwiftPM in Bazel
Bonus: Move Code Generation to Bazel
> Mostly done
> No longer have to codegen unnecessarily
Replace CocoaPods & Carthage With SwiftPM for Dependency Resolution
> Done, but removed SwiftPM due to reliability issues (mostly with CI builds) (SR-10718)
> Now Bazel is downloading hard-coded dependencies
Current Status
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Clean Build Times
No Cache
With Cache
0 6m 12m 18m 24m 30m
Bazel Xcode
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Improve Developer Experience
> Code viewer & breakpoints working in Xcode with Tulsi
> Code completion is not complete
> Making modifications to code built by Bazel not great
Remaining Issues
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> Split up codebase into more modules
> Needed for true gains in incremental build times
Build More in Bazel
Improve Developer Experience
> Code viewer & breakpoints working in Xcode with Tulsi
> Code completion is not complete
> Making modifications to code built by Bazel not great
Remaining Issues
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> Split up codebase into more modules
> Needed for true gains in incremental build times
Build More in Bazel
Cache Reusability
> Some differences between machines prevent build cache reuse
> Mostly resolved
Improve Developer Experience
> Code viewer & breakpoints working in Xcode with Tulsi
> Code completion is not complete
> Making modifications to code built by Bazel not great
Remaining Issues
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Thank You
Also Check Out
15:30-15:40 Short Track - “Faster iOS Builds With Bazel”