It is a non-transitive R class world
5 min read
After Duplo modularization, we seen that the duty producing a transitive R class was taking a big period of time to execute. To get rid of this activity altogether, and because the non-transitive R class is marketed to have as much as 40% incremental build time improvement, we determined emigrate our codebase to make use of it.
For those who’re not aware of nonTransitiveRClass, beforehand generally known as namespacedRclass, it’s an Android Gradle Plugin flag that permits namespacing R lessons so that each module’s R class solely consists of assets declared within the module itself, and never assets from the modules or libraries it is dependent upon. This flag is enabled by default for brand new initiatives since Android Studio Bumblebee.
On this put up, we’ll stroll by means of how we transitioned to non-transitive R class and a few of the advantages — each anticipated and sudden — that we noticed.
Establishing conventions
Kotlin
Since assets can’t all be referenced utilizing the present module’s R class anymore, we first wanted to align on how we wished them to be referenced within the non-transitive R class world. Utilizing the fully-qualified identify for R lessons to reference assets, e.g. getString(slack.l10n.R.string.at_everyone), was cumbersome and verbose, so we settled on utilizing import aliases as an alternative for that goal:
import slack.l10n.R as L10nR
class Clazz(context: Context)
init
context.getString(L10nR.string.at_everyone)
Java
Sadly, import aliases are a Kotlin-specific function and never obtainable in Java. Nonetheless, contemplating that solely 4% of our codebase was nonetheless in Java, we agreed that utilizing the fully-qualified identify to reference assets not declared within the present module was a ok resolution, and would function motivation emigrate these lessons to Kotlin down the road.
Migration
Preliminary technique
We had been planning on utilizing Android Studio’s Refactor > Migrate to Non-Transitive R Classes function to refactor all R references to be fully-qualified, after which use this script to undergo the refactored information and alter the fully-qualified references to make use of import aliases.
Nonetheless, on the scale of our codebase, with greater than 400 modules, Android Studio took all evening on an Intel Macbook Professional (we hadn’t but moved to M1 Macs) to do a part of the work and brought on the UI to grow to be non-responsive after, so we pivoted to a unique migration technique.
Chosen technique
The vast majority of our assets are outlined in two modules: the strings are in :l10n-strings and most different assets are in :slack-kit-resources. So, we proceeded with the next technique:
- We first used Android Studio’s Discover & Exchange with the regex
([[|(|]| )R.string.to interchange string useful resource references with$1L10nR.string.and the regex([[|(|]| )R.(colour|dimen|drawable|font|uncooked|model|attr).sk_to interchange different useful resource references with$1SlackKitR.$2.sk_. - Then we ran a modified model of the aforementioned script to iterate over information that used both
L10nRorSlackKitRas a useful resource reference and added the mandatory import aliases to them. The wanted dependencies had been added to the modules that had been beforehand relying on both:l10n-stringsor:slack-kit-resourcestransitively by means of the R class. The mission began compiling efficiently once more. - We enabled non-transitive R class by including
android.nonTransitiveRClass=trueto the foundation gradle.properties file, and manually up to date the few remaining useful resource references that had been failing compilation. - As the ultimate step of the migration, we enabled a non-transitive R class dependent optimization that generates the compile time solely R class utilizing the app’s native assets by including
android.enableAppCompileTimeRClass=trueto the identical gradle.properties file.
Developer expertise
Discoverability enhancements
To assist builders work as successfully within the non-transitive R class world as they did earlier than, we discovered the 4 most typical import aliases within the codebase, by operating grep -o -h -r -E 'import w+(.w+)+.R as [a-zA-Z0-9]+R' . | kind | uniq -c | kind -b -n -r, and added them as live templates that begin with r for discoverability.
Not like file and code templates, reside templates can’t be made obtainable to everybody who works on the mission by means of Intellij. To work round this, we copied the reside templates file from Android Studio’s templates listing in ~/Library/Software Assist/Google/AndroidStudio<model> and checked it into our Git repository beneath the config/templates listing. As a technique to import it into Android Studio at any time when a brand new model is put in, we then used this script, which runs as a part of bootstrapping the native improvement surroundings, to repeat the live templates file again to the templates listing.
Conference enforcement
Along with the reside templates, we additionally developed three lint checks, that constructed on high of the conventions that we agreed on, to enforced the next:
- Solely the native module’s R class could be imported with out an import alias.
- For instance,
slack.uikit.assets.Rcan’t be imported exterior:slack-kit-resourceswith out an import alias.
- For instance,
- Import aliases for R lessons needs to be constant throughout the codebase.
- For instance,
slack.uikit.assets.Rcan solely be imported asSlackKitR, notSKRor the rest.
- For instance,
- R lessons/assets can’t be referenced utilizing their fully-qualified names, however slightly by means of import aliases.
- For instance,
getString(L10nR.string.at_everyone)must be used as an alternative ofgetString(slack.l10n.R.string.at_everyone).
- For instance,
All three lint checks have auto-fixes, so fixing any ensuing lint points is a breeze.
Advantages
Migrating to non-transitive R class had many advantages, essentially the most notable being a ~14% enchancment in incremental construct occasions following a useful resource or structure change.
It additionally diminished APK/DEX dimension by ~8.5%, which is about 5.5MB of code!
Along with the advantages lined above, which had been anticipated, the transition had some oblique advantages that had been sudden:
- It uncovered cases the place some assets had been declared in a single module however solely utilized in one other, which allowed us to maneuver them for elevated module cohesion.
- It made it simpler to determine the place assets are coming from, which enabled us to slim down inaccessible UI components and triage them.
Conclusion
All in all, the migration to non-transitive R class has been an enormous success for us, and developer sentiment is optimistic because of all its advantages and the tooling we applied as assist.
We suggest you make the transition to non-transitive R class to reap the advantages we’ve outlined if you’re engaged on a multi-module mission or plan on introducing modules to your mission.
For those who like engaged on stuff like this, we’re hiring!
