From 0574c2100dfd27c073d0f2ca4ee64cc0a1cd6609 Mon Sep 17 00:00:00 2001 From: Nik Clayton Date: Thu, 20 Jun 2024 19:13:02 +0200 Subject: [PATCH] docs: Add an ADR explaining why Kotlin is used --- docs/decisions/0002-use-kotlin.md | 50 +++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 docs/decisions/0002-use-kotlin.md diff --git a/docs/decisions/0002-use-kotlin.md b/docs/decisions/0002-use-kotlin.md new file mode 100644 index 000000000..ef73084cd --- /dev/null +++ b/docs/decisions/0002-use-kotlin.md @@ -0,0 +1,50 @@ +# Use Kotlin + +## Context and Problem Statement + +Android applications can be written in Java, Kotlin, or a mix of the two. What should the project choose? + +## Considered Options + +* Use Kotlin for all new code, migrate existing code +* Allow new code to be Kotlin or Java +* Use Java for all new code, migrate existing code + +## Decision Outcome + +Chosen option: "Use Kotlin for all new code, migrate existing code", because comes out best (see below). + +### Consequences + +* Good, because it simplifies the number of languages contributors need to know +* Good, because Kotlin has features that mitigate issues that require third party libraries in Java (null pointer exceptions, immutable collections, etc) +* Good, because Kotlin's support for structured concurrency resolves an entire class of bugs +* Good, because Android ecosystem, especially Google libraries, is increasingly moving to Kotlin. Google describes Kotlin as part of [Modern Android Development](https://developer.android.com/modern-android-development) +* Bad, because contributing to third party libraries used by the app may still require Java +* Bad, because Kotlin may be unfamiliar to potential contributors +* Neutral, because tools exist to automatically convert Java to equivalent (but possibly not idiomatic) Kotlin + +## Pros and Cons of the Options + +### Use Kotlin for all new code, migrate existing code + +* Good, because the number of languages contributors need to know remains low +* Good, because Kotlin has features that mitigate issues that require third party libraries in Java (null pointer exceptions, immutable collections, etc) +* Good, because Kotlin's support for structured concurrency resolves an entire class of bugs +* Good, because Android ecosystem, especially Google libraries, is increasingly moving to Kotlin. Google describes Kotlin as part of [Modern Android Development](https://developer.android.com/modern-android-development) +* Bad, because contributing to third party libraries used by the app may still require Java +* Bad, because Kotlin may be unfamiliar to potential contributors +* Neutral, because tools exist to automatically convert Java to equivalent (but possibly not idiomatic) Kotlin + +### Allow new code to be Kotlin or Java + +* Good, because it may be easier to attract new contributors already familiar with Java +* Bad, because a single PR may need to modify code in both languages, so contributors likely still need to be familiar with both +* Bad, because anyone conducting PR reviews must be familiar with both languages +* Bad, because although Java and Kotlin can interop it requires additional annotations and sometimes code on the Kotlin side, making the code more complicated + +### Use Java for all new code, migrate existing code + +* Bad, because this is the opposite direction the Android ecosystem is moving in +* Bad, because Kotlin brings significant improvements to Java that would be thrown out +* Bad, because additional work