Faster iOS Builds with Bazel

TruongThi Doan
LINE App Dev 4 Software Engineer
https://linedevday.linecorp.com/jp/2019/sessions/S2-9

Transcript

1. 2019 DevDay
   Faster iOS Builds With Bazel
   > TruongThi Doan
   > LINE App Dev 4 Software Engineer
   

   View Slide

2. Agenda > Problems
   > Challenges
   > Room for Improvement
   

   View Slide

3. Overview
   LINE iOS
   Modules
   224
   Lines of Code
   1.4m
   Source Files
   8.4k
   

   View Slide

4. Problems
   > “Works on my machine” problems
   > Release builds must be full clean builds
   > Long build times as project grows
   

   View Slide

5. https://bazel.build
   Bazel
   Growing LINE for iOS • Thursday, 14:30
   > Fast & Reproducible
   > Remote Caching
   > Extensible
   

   View Slide

6. Incremental Adoption
   Prebuilt Static Frameworks
   Ƃ
   load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
   swift_library(
   name = "LineServices",
   srcs = glob(["*.swift"]),
   deps = [":Thrift"],
   )
   

   View Slide

7. Incremental Adoption
   Prebuilt Static Frameworks
   Ƃ
   load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
   load("@build_bazel_rules_apple//apple:ios.bzl", "ios_static_framework")
   swift_library(
   name = "LineServices",
   srcs = glob(["*.swift"]),
   deps = [":Thrift"],
   )
   ios_static_framework(
   name = "LineServicesFramework",
   bundle_name = "LineServices",
   minimum_os_version = "11.0",
   deps = [":LineServices"],
   )
   

   View Slide

8. > Swift dependencies
   Carthage
   Git Submodules
   > Dependencies that aren’t directly related to iOS
   CocoaPods
   > Objective-C dependencies
   Dependencies
   

   View Slide

9. > Pod2BUILD
   > Manually writing BUILD files
   Objective-C static frameworks
   Swift static frameworks
   > .swiftdoc & .swiftmodule weren’t bundled
   > Post-processing ios_static_framework()
   Cont’d
   Dependencies
   

   View Slide

10. Mixed Objective-C & Swift
    Frameworks
    

    View Slide

11. Mixed Targets
    > Generating module map
    from Obj-C headers
    Ƃ
    native.genrule(
    name = "objc_module_map",
    srcs = hdrs,
    outs = ["module.modulemap"],
    cmd = """
    echo "module {} {{" >> $@
    for src in $(SRCS); do
    echo " header \\"$${{src}}\\"" >> $@
    done
    echo "}}" >> $@
    """.format(module_name),
    )
    

    View Slide

12. Mixed Targets
    > Generating module map
    from Obj-C headers
    > swift_library() with all
    Swift source files
    Ƃ
    native.swift_library(
    name = "LineServices",
    module_name = "LineServices",
    srcs = native.glob(["*.swift"]),
    copts = [
    "-import-underlying-module",
    "-Xfrontend",
    "-enable-objc-interop",
    "-Xcc",
    "-fmodule-map-file=$(execpath :module.modulemap)",
    ],
    swiftc_inputs = hdrs + ["module.modulemap"],
    features = ["swift.no_generated_module_map"],
    )
    

    View Slide

13. Mixed Targets
    > Generating module map
    from Obj-C headers
    > swift_library() with all
    Swift source files
    > objc_library() with all
    Obj-C source files
    Ƃ
    native.objc_library(
    name = "LineServices_umbrella",
    module_name = "LineServices",
    hdrs = hdrs,
    srcs = native.glob(["*.m"]),
    deps =[":LineServices"],
    )
    

    View Slide

14. Ƃ
    Local Development
    > Generating Xcode project from
    BUILD files with Tulsi
    > Breakpoints work by overriding
    an LLDB setting
    # ~/.lldbinit
    settings set target.source-map "./" "~/line-ios/"
    

    View Slide

15. Remote Caching
    > Any HTTP/1.1 backend
    > Google Cloud Storage
    > bazel-remote
    • github.com/buchgr/bazel-remote
    > Don’t use Bazel 1.1
    Ƃ
    

    View Slide

16. Clean Build Times
    No Cache
    With Cache
    0෼ 6෼ 12෼ 18෼ 24෼ 30෼
    Bazel
    Xcode
    

    View Slide

17. Room for Improvement
    > Developer experience
    > Improving shared remote cache
    > Swift Package Manager support
    

    View Slide

18. Thank You
    

    View Slide