It is a non-transitive R class world
After Duplo modularization, we seen that the duty producing a transitive R class was taking a big period of time to execute. To remove this job altogether, and for the reason that 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 often called namespacedRclass, it’s an Android Gradle Plugin flag that allows namespacing R courses so that each module’s R class solely consists of sources declared within the module itself, and never sources from the modules or libraries it will depend on. This flag is enabled by default for brand new tasks since Android Studio Bumblebee.
On this put up, we’ll stroll by means of how we transitioned to non-transitive R class and a number of the advantages — each anticipated and surprising — that we noticed.
Establishing conventions
Kotlin
Since sources 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 courses to reference sources, e.g. getString(slack.l10n.R.string.at_everyone)
, was cumbersome and verbose, so we settled on utilizing import aliases as a substitute for that function:
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 characteristic 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 sources not declared within the present module was a adequate resolution, and would function motivation emigrate these courses to Kotlin down the road.
Migration
Preliminary technique
We had been planning on utilizing Android Studio’s Refactor > Migrate to Non-Transitive R Classes characteristic to refactor all R references to be fully-qualified, after which use this script to undergo the refactored recordsdata 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 prompted the UI to turn into non-responsive after, so we pivoted to a unique migration technique.
Chosen technique
The vast majority of our sources are outlined in two modules: the strings are in :l10n-strings
and most different sources are in :slack-kit-resources
. So, we proceeded with the next technique:
- We first used Android Studio’s Discover & Change with the regex
([[|(|]| )R.string.
to switch string useful resource references with$1L10nR.string.
and the regex([[|(|]| )R.(coloration|dimen|drawable|font|uncooked|fashion|attr).sk_
to switch different useful resource references with$1SlackKitR.$2.sk_
. - Then we ran a modified model of the aforementioned script to iterate over recordsdata that used both
L10nR
orSlackKitR
as a useful resource reference and added the required import aliases to them. The wanted dependencies had been added to the modules that had been beforehand relying on both:l10n-strings
or:slack-kit-resources
transitively by means of the R class. The undertaking began compiling efficiently once more. - We enabled non-transitive R class by including
android.nonTransitiveRClass=true
to the basis 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 sources by including
android.enableAppCompileTimeRClass=true
to 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.
In contrast to file and code templates, reside templates can’t be made obtainable to everybody who works on the undertaking 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 below the config/templates listing. As a option 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 growth setting, 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.sources.R
can’t be imported outdoors:slack-kit-resources
with out an import alias.
- For instance,
- Import aliases for R courses must be constant throughout the codebase.
- For instance,
slack.uikit.sources.R
can solely be imported asSlackKitR
, notSKR
or anything.
- For instance,
- R courses/sources can’t be referenced utilizing their fully-qualified names, however fairly by means of import aliases.
- For instance,
getString(L10nR.string.at_everyone)
needs to be used as a substitute 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, probably the most notable being a ~14% enchancment in incremental construct occasions following a useful resource or format change.
It additionally lowered APK/DEX dimension by ~8.5%, which is about 5.5MB of code!
Along with the advantages coated above, which had been anticipated, the transition had some oblique advantages that had been surprising:
- It uncovered situations the place some sources 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 sources are coming from, which enabled us to slender down inaccessible UI parts and triage them.
Conclusion
All in all, the migration to non-transitive R class has been a giant success for us, and developer sentiment is optimistic because of all its advantages and the tooling we carried out as assist.
We suggest you make the transition to non-transitive R class to reap the advantages we’ve outlined in case you are engaged on a multi-module undertaking or plan on introducing modules to your undertaking.
For those who like engaged on stuff like this, we’re hiring!