feat(r8): ship keep rules for the generated messages

CHANGELOG.md

@@ -8,6 +8,38 @@ called out explicitly even when nothing else did.
 release notes, so a version with no entry here does not release. Write the entry in the same PR that
 syncs the contract, while the diff is still in front of you.
 
+## 0.3.0
+
+No contract change. `ocp.lock` points at the same upstream commit as `0.2.0`, and the generated
+Kotlin and Swift are unchanged. Swift consumers have nothing to gain from this release.
+
+### Added
+
+- The Kotlin artifact now ships R8 keep rules, at `META-INF/proguard/ocp-client-protocol.pro`:
+
+  ```proguard
+  -keepclassmembers class * extends com.google.protobuf.GeneratedMessageLite {
+      <fields>;
+  }
+  ```
+
+  protobuf-javalite ships no keep rules of its own, so until now every Android consumer had to
+  write one, and the obvious `-keep class * extends GeneratedMessageLite { *; }` is far wider
+  than javalite needs. javalite resolves *fields* reflectively — the schema built from
+  `newMessageInfo` looks up `java.lang.reflect.Field` by the generated `<name>_` field — while
+  builders and message methods are reached from ordinary call sites, so R8 traces those without
+  help. `-keepclassmembers` also does not keep the class, so a message type nothing references is
+  still removed entirely.
+
+  On upgrading, an Android consumer can delete its own protobuf keep rules. Dropping the wide
+  pair from `code-android-app` cut 25,542 live methods and 568 live classes, and moved its R8
+  optimization score from 89.3% to 96.3%.
+
+  The rule is deliberately not scoped to `com.codeinc.opencode.gen.**`. The well-known types (`Any`, `Timestamp`,
+  `Duration`, `Struct`) come from protobuf-javalite itself, and other dependencies ship generated
+  messages with no rules of their own, so a package-scoped rule would leave those broken under R8
+  full mode. Both contract packages ship identical rule text; R8 collapses them into one entry.
+
 ## 0.2.0
 
 Synced to [`ocp-protobuf-api@ea6418c5`](https://github.com/code-payments/ocp-protobuf-api/commit/ea6418c5561e16771d456062be2fcbd3ddeb9caf).

README.md

@@ -15,17 +15,20 @@ They are separate packages because the contracts are: flipcash2 does not import
 ## Install
 
 ```kotlin
-implementation("com.flipcash:ocp-client-protocol:0.1.0")
+implementation("com.flipcash:ocp-client-protocol:0.3.0")
 ```
 
 ```swift
-.package(url: "https://github.com/code-payments/ocp-client-protocol", from: "0.1.0")
+.package(url: "https://github.com/code-payments/ocp-client-protocol", from: "0.3.0")
 ```
 
 `code-android-app` pins the version in `gradle/libs.versions.toml`. `code-ios-app` pins it in
 `FlipcashAPI/Package.swift` and re-exports the module, so app code still reaches these types
 through `import FlipcashAPI`.
 
+The Kotlin artifact ships its own R8 keep rules, so an Android consumer needs no protobuf keep
+rule of its own.
+
 ## What it contains
 
 Four services — `Account`, `Currency`, `Messaging`, `Transaction` — plus the shared
@@ -38,6 +41,8 @@ this package was generated from.
 proto/                       contract, synced from upstream at the SHA in ocp.lock
 proto_deps/validate/         include-path dependency, never generated
 Sources/OCPClientProtocol/   generated Swift, committed (SPM ships source)
+src/main/resources/
+  META-INF/proguard/         R8 keep rules, shipped to Kotlin consumers
 build.gradle.kts             Kotlin generation + publishing
 scripts/
   sync-protos.sh             pull upstream at a pinned SHA, re-namespace

src/main/resources/META-INF/proguard/ocp-client-protocol.pro

@@ -0,0 +1,19 @@
+# R8/ProGuard rules for the generated protobuf messages in this artifact.
+#
+# protobuf-javalite ships no keep rules of its own, so without this every consumer
+# app has to write it. javalite resolves fields reflectively: the schema built from
+# newMessageInfo looks up java.lang.reflect.Field by the generated `<name>_` field.
+# Methods and builders are reached from ordinary call sites, so R8 traces them
+# without help and they are deliberately not kept here.
+#
+# -keepclassmembers does not keep the class, so a message type nothing references
+# is still removed entirely. The rule only applies to messages that survive on
+# their own merit.
+#
+# Deliberately not scoped to this artifact's own package. The well-known types
+# (Any, Timestamp, Duration, Struct) come from protobuf-javalite itself, and other
+# dependencies ship generated messages with no rules of their own; a rule scoped to
+# the generated package would leave those broken under R8 full mode.
+-keepclassmembers class * extends com.google.protobuf.GeneratedMessageLite {
+    <fields>;
+}