Added one more test and better message

Author: Mr3zee

compiler-plugin/compiler-plugin-k2/src/main/kotlin/kotlinx/rpc/codegen/checkers/diagnostics/RpcDiagnosticRendererFactory.kt

@@ -115,7 +115,8 @@ object GrpcDiagnosticRendererFactory : BaseDiagnosticRendererFactory() {
 
         map.put(
             factory = FirGrpcDiagnostics.WRONG_SAFE_IDEMPOTENT_COMBINATION,
-            message = "'safe = true' and 'idempotent = false' are mutually exclusive.",
+            message = "'safe = true' and 'idempotent = false' are mutually exclusive. " +
+                    "If the method is safe, write explicitly 'idempotent = true'.",
         )
 
         map.put(

tests/compiler-plugin-tests/src/testData/diagnostics/grpc.fir.txt

@@ -65,7 +65,9 @@ FILE: module_main_grpc.kt
 
         @R|kotlinx/rpc/grpc/annotations/Grpc.Method|(name = <strcat>(String(wrongName), String(+3))) public abstract suspend fun wrongName3(): R|kotlin/Unit|
 
-        @R|kotlinx/rpc/grpc/annotations/Grpc.Method|(safe = Boolean(true), idempotent = Boolean(false)) public abstract suspend fun wrongSafeIdempotent(): R|kotlin/Unit|
+        @R|kotlinx/rpc/grpc/annotations/Grpc.Method|(safe = Boolean(true), idempotent = Boolean(false)) public abstract suspend fun wrongSafeIdempotent1(): R|kotlin/Unit|
+
+        @R|kotlinx/rpc/grpc/annotations/Grpc.Method|(safe = Boolean(true)) public abstract suspend fun wrongSafeIdempotent2(): R|kotlin/Unit|
 
         public final class $rpcServiceStub : R|kotlin/Any| {
             public final companion object Companion : R|kotlin/Any| {

tests/compiler-plugin-tests/src/testData/diagnostics/grpc.kt

@@ -53,5 +53,8 @@ interface WrongAnnotations4 {
     suspend fun wrongName3()
 
     @Grpc.Method<!WRONG_SAFE_IDEMPOTENT_COMBINATION!>(safe = true, idempotent = false)<!>
-    suspend fun wrongSafeIdempotent()
+    suspend fun wrongSafeIdempotent1()
+
+    @Grpc.Method<!WRONG_SAFE_IDEMPOTENT_COMBINATION!>(safe = true)<!>
+    suspend fun wrongSafeIdempotent2()
 }