TW-5091: nullable calendar color id fix

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+### Fixed
+* `UpdateEventRequest.Builder.clearColorId()` now sends `"color_id": null` to the Nylas API, allowing event colors to be cleared. Previously, setting `colorId` to `null` was silently omitted from the request body due to Moshi's default null-skipping behavior, leaving the existing color unchanged. (#324)
 ### Changed
 * Extended `EventResource` with additional room metadata fields: `capacity` (`Int`), `building` (`String`), `floorName` / `floor_name` (`String`), `floorSection` / `floor_section` (`String`), and `floorNumber` / `floor_number` (`Int`) — all optional, defaulting to `null`
 

src/main/kotlin/com/nylas/models/NullableField.kt

@@ -0,0 +1,17 @@
+package com.nylas.models
+
+/**
+ * Represents a field that can be explicitly set to null (to clear its value on the server)
+ * or left absent from the request payload entirely.
+ *
+ * - Leave the field as Kotlin null to omit it from serialization (no change to server value).
+ * - Use [Clear] to send `null` explicitly and clear the server-side value.
+ * - Use [Value] to send a specific value.
+ */
+sealed class NullableField<out T> {
+  /** Serialize the field as JSON null, signalling the server to clear the value. */
+  object Clear : NullableField<Nothing>()
+
+  /** Serialize the field with the given value. */
+  data class Value<T>(val v: T) : NullableField<T>()
+}

src/main/kotlin/com/nylas/models/UpdateEventRequest.kt

@@ -100,7 +100,7 @@ data class UpdateEventRequest(
    * @see <a href="https://developers.google.com/calendar/api/v3/reference/colors">Google Calendar Colors</a>
    */
   @Json(name = "color_id")
-  val colorId: String? = null,
+  val colorId: NullableField<String>? = null,
   /**
    * List of resources (e.g. rooms) to associate with the event.
    */
@@ -609,7 +609,7 @@ data class UpdateEventRequest(
     private var capacity: Int? = null
     private var hideParticipant: Boolean? = null
     private var notetaker: EventNotetakerRequest? = null
-    private var colorId: String? = null
+    private var colorId: NullableField<String>? = null
     private var resources: List<EventResource>? = null
 
     /**
@@ -740,7 +740,14 @@ data class UpdateEventRequest(
      * @return The builder.
      * @see <a href="https://developers.google.com/calendar/api/v3/reference/colors">Google Calendar Colors</a>
      */
-    fun colorId(colorId: String) = apply { this.colorId = colorId }
+    fun colorId(colorId: String) = apply { this.colorId = NullableField.Value(colorId) }
+
+    /**
+     * Clear the Google color ID for the event, reverting to the calendar default.
+     * Sends `"color_id": null` in the request body.
+     * @return The builder.
+     */
+    fun clearColorId() = apply { this.colorId = NullableField.Clear }
 
     /**
      * Update the list of resources (e.g. rooms) to associate with the event.

src/main/kotlin/com/nylas/util/JsonHelper.kt

@@ -49,6 +49,7 @@ class JsonHelper {
       .add(MicrosoftAdminConsentCredentialDataAdapter())
       .add(GoogleServiceAccountCredentialDataAdapter())
       .add(ConnectorOverrideCredentialDataAdapter())
+      .add(NullableFieldAdapterFactory())
       // Polymorphic adapters
       .add(WHEN_JSON_FACTORY)
       .add(FREE_BUSY_JSON_FACTORY)

src/main/kotlin/com/nylas/util/NullableFieldAdapterFactory.kt

@@ -0,0 +1,57 @@
+package com.nylas.util
+
+import com.nylas.models.NullableField
+import com.squareup.moshi.JsonAdapter
+import com.squareup.moshi.JsonReader
+import com.squareup.moshi.JsonWriter
+import com.squareup.moshi.Moshi
+import com.squareup.moshi.Types
+import java.lang.reflect.ParameterizedType
+import java.lang.reflect.Type
+
+/**
+ * Moshi adapter factory for [NullableField].
+ * - Kotlin null field → field omitted from JSON (handled by KotlinJsonAdapterFactory before us)
+ * - [NullableField.Clear] → `"field": null`
+ * - [NullableField.Value] → `"field": <value>`
+ * @suppress Not for public use.
+ */
+class NullableFieldAdapterFactory : JsonAdapter.Factory {
+  override fun create(type: Type, annotations: Set<Annotation>, moshi: Moshi): JsonAdapter<*>? {
+    if (Types.getRawType(type) != NullableField::class.java) return null
+    val innerType = (type as ParameterizedType).actualTypeArguments[0]
+
+    @Suppress("UNCHECKED_CAST")
+    val innerAdapter = moshi.adapter<Any>(innerType) as JsonAdapter<Any>
+    return NullableFieldAdapter(innerAdapter)
+  }
+
+  private class NullableFieldAdapter<T : Any>(
+    private val innerAdapter: JsonAdapter<T>,
+  ) : JsonAdapter<NullableField<T>>() {
+    override fun toJson(writer: JsonWriter, value: NullableField<T>?) {
+      when (value) {
+        is NullableField.Clear -> {
+          // JsonWriter drops nullValue() silently when serializeNulls=false.
+          // Force it on just for this write so the explicit null reaches the wire.
+          val prev = writer.serializeNulls
+          writer.serializeNulls = true
+          writer.nullValue()
+          writer.serializeNulls = prev
+        }
+        is NullableField.Value -> innerAdapter.toJson(writer, value.v)
+        null -> writer.nullValue()
+      }
+    }
+
+    override fun fromJson(reader: JsonReader): NullableField<T>? {
+      return if (reader.peek() == JsonReader.Token.NULL) {
+        reader.nextNull<Any>()
+        NullableField.Clear
+      } else {
+        @Suppress("UNCHECKED_CAST")
+        NullableField.Value(innerAdapter.fromJson(reader) as T)
+      }
+    }
+  }
+}

src/test/kotlin/com/nylas/resources/EventsTests.kt

@@ -17,6 +17,7 @@ import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFalse
 import kotlin.test.assertIs
+import kotlin.test.assertNull
 import kotlin.test.assertTrue
 
 class EventsTests {
@@ -534,7 +535,7 @@ class EventsTests {
     @Test
     fun `UpdateEventRequest with colorId serializes color_id field`() {
       val adapter = JsonHelper.moshi().adapter(UpdateEventRequest::class.java)
-      val request = UpdateEventRequest(colorId = "11")
+      val request = UpdateEventRequest(colorId = NullableField.Value("11"))
 
       val jsonMap = JsonHelper.moshi().adapter(Map::class.java).fromJson(adapter.toJson(request))!!
       assertEquals("11", jsonMap["color_id"])
@@ -549,6 +550,51 @@ class EventsTests {
       assertFalse(json.contains("color_id"))
     }
 
+    @Test
+    fun `UpdateEventRequest with clearColorId serializes color_id as null`() {
+      val adapter = JsonHelper.moshi().adapter(UpdateEventRequest::class.java)
+      val request = UpdateEventRequest.Builder().clearColorId().build()
+
+      val json = adapter.toJson(request)
+      val jsonMap = JsonHelper.moshi().adapter(Map::class.java).fromJson(json)!!
+      assertTrue(jsonMap.containsKey("color_id"))
+      assertNull(jsonMap["color_id"])
+    }
+
+    @Test
+    fun `UpdateEventRequest Builder colorId method serializes color_id field`() {
+      val adapter = JsonHelper.moshi().adapter(UpdateEventRequest::class.java)
+      val request = UpdateEventRequest.Builder().colorId("9").build()
+
+      val jsonMap = JsonHelper.moshi().adapter(Map::class.java).fromJson(adapter.toJson(request))!!
+      assertEquals("9", jsonMap["color_id"])
+    }
+
+    @Test
+    fun `UpdateEventRequest with color_id value in JSON deserializes to NullableField Value`() {
+      val adapter = JsonHelper.moshi().adapter(UpdateEventRequest::class.java)
+      val request = adapter.fromJson("""{"color_id":"5"}""")
+
+      assertIs<NullableField.Value<String>>(request?.colorId)
+      assertEquals("5", (request?.colorId as NullableField.Value).v)
+    }
+
+    @Test
+    fun `UpdateEventRequest with null color_id in JSON deserializes to NullableField Clear`() {
+      val adapter = JsonHelper.moshi().adapter(UpdateEventRequest::class.java)
+      val request = adapter.fromJson("""{"color_id":null}""")
+
+      assertIs<NullableField.Clear>(request?.colorId)
+    }
+
+    @Test
+    fun `UpdateEventRequest with colorId roundtrips through serialization correctly`() {
+      val adapter = JsonHelper.moshi().adapter(UpdateEventRequest::class.java)
+      val original = UpdateEventRequest.Builder().colorId("3").build()
+
+      assertEquals(original, adapter.fromJson(adapter.toJson(original)))
+    }
+
     @Test
     fun `Event with existing ConferencingProvider still works properly`() {
       // This test verifies that the original Event model continues to work with the original ConferencingProvider enum
@@ -1055,7 +1101,7 @@ class EventsTests {
               transcription = true,
             ),
           ),
-          colorId = "11",
+          colorId = NullableField.Value("11"),
         )
       val updateEventQueryParams =
         UpdateEventQueryParams(

src/test/kotlin/com/nylas/util/NullableFieldAdapterFactoryTest.kt

@@ -0,0 +1,38 @@
+package com.nylas.util
+
+import com.nylas.models.NullableField
+import com.squareup.moshi.Types
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertIs
+import kotlin.test.assertNull
+
+class NullableFieldAdapterFactoryTest {
+  private val moshi = JsonHelper.moshi()
+  private val adapter = moshi.adapter<NullableField<String>>(
+    Types.newParameterizedType(NullableField::class.java, String::class.java),
+  )
+
+  @Test
+  fun `create returns null for non-NullableField type`() {
+    val result = NullableFieldAdapterFactory().create(String::class.java, emptySet(), moshi)
+    assertNull(result)
+  }
+
+  @Test
+  fun `toJson with null NullableField writes JSON null`() {
+    assertEquals("null", adapter.toJson(null))
+  }
+
+  @Test
+  fun `fromJson with JSON null returns NullableField Clear`() {
+    assertIs<NullableField.Clear>(adapter.fromJson("null"))
+  }
+
+  @Test
+  fun `fromJson with JSON string returns NullableField Value`() {
+    val result = adapter.fromJson("\"hello\"")
+    assertIs<NullableField.Value<String>>(result)
+    assertEquals("hello", result.v)
+  }
+}