Support bool map keys in Moshi and Gson JSON adapters

wire-runtime/src/jvmMain/kotlin/com/squareup/wire/internal/JsonIntegration.kt

@@ -135,6 +135,7 @@ abstract class JsonIntegration<F, A> {
 
   private fun mapKeyJsonFormatter(protoAdapter: ProtoAdapter<*>): JsonFormatter<*> = when (protoAdapter) {
     ProtoAdapter.STRING -> StringJsonFormatter
+    ProtoAdapter.BOOL -> BooleanAsStringJsonFormatter
     ProtoAdapter.INT32,
     ProtoAdapter.SINT32,
     ProtoAdapter.SFIXED32,
@@ -236,6 +237,17 @@ abstract class JsonIntegration<F, A> {
     override fun toStringOrNumber(value: Int) = value.toString()
   }
 
+  /** Encodes a boolean value with quotes, like `"true"`. */
+  private object BooleanAsStringJsonFormatter : JsonFormatter<Boolean> {
+    override fun fromString(value: String) = when (value) {
+      "true" -> true
+      "false" -> false
+      else -> throw IllegalArgumentException("expected true or false but was $value")
+    }
+
+    override fun toStringOrNumber(value: Boolean) = value.toString()
+  }
+
   /** Encodes a byte string as base64. */
   private object ByteStringJsonFormatter : JsonFormatter<ByteString> {
     override fun toStringOrNumber(value: ByteString) = value.base64()

wire-tests/fixtures/shared/proto/proto3/map_types.proto

@@ -30,3 +30,7 @@ message MapTypes {
   map<fixed64, fixed64> map_fixed64_fixed64 = 10;
   map<uint64, uint64> map_uint64_uint64 = 11;
 }
+
+message MapBoolKeys {
+  map<bool, string> map_bool_string = 1;
+}

wire-tests/wire-json-shared-kotlin-tests/com/squareup/wire/WireJsonTest.kt

@@ -49,6 +49,7 @@ import squareup.proto3.CamelCase.NestedCamelCase
 import squareup.proto3.ContainsFieldMask
 import squareup.proto3.FreeDrinkPromotion
 import squareup.proto3.FreeGarlicBreadPromotion
+import squareup.proto3.MapBoolKeys
 import squareup.proto3.MapTypes
 import squareup.proto3.Pizza
 import squareup.proto3.PizzaDelivery
@@ -913,6 +914,17 @@ class WireJsonTest {
     )
   }
 
+  @Test fun mapBoolKeys() {
+    val value = MapBoolKeys.Builder()
+      .map_bool_string(mapOf(true to "yes", false to "no"))
+      .build()
+    val fieldName = if (jsonLibrary.preservingProtoFieldNames) "map_bool_string" else "mapBoolString"
+    val json = """{"$fieldName":{"true":"yes","false":"no"}}"""
+
+    assertJsonEquals(json, jsonLibrary.toJson(value, MapBoolKeys::class.java))
+    assertThat(jsonLibrary.fromJson(json, MapBoolKeys::class.java)).isEqualTo(value)
+  }
+
   @Test fun all32MaxValue() {
     val value = All32.Builder()
       .my_int32(Int.MAX_VALUE)