Added a Variables test

apollo-api/src/commonMain/kotlin/com/apollographql/apollo3/api/Optional.kt

@@ -12,7 +12,7 @@ sealed class Optional<out V> {
   fun getOrNull() = (this as? Present)?.value
   fun getOrThrow() = getOrNull() ?: throw MissingValueException()
 
-  class Present<V>(val value: V) : Optional<V>()
+  data class Present<V>(val value: V) : Optional<V>()
   object Absent : Optional<Nothing>()
 
   fun <V : Any> presentIfNotNull(value: V?): Optional<V> = if (value == null) Absent else Present(value)

composite/tests/integration-tests-kotlin/src/commonTest/kotlin/test/variables/VariablesTest.kt

@@ -0,0 +1,52 @@
+package test.variables
+
+import com.apollographql.apollo3.api.Optional
+import variables.NonNullVariableWithDefaultValueQuery
+import variables.NullableVariableQuery
+import variables.NullableVariableWithDefaultValueQuery
+import variables.NullableVariableWithOptionalDirectiveQuery
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class VariablesTest {
+  @Test
+  fun nullableVariableDefaultsToNonOptional() {
+    /**
+     * By default, we remove the `Optional` so that users have to input a parameter
+     * It's not possible to omit a variable. But it is possible to send null
+     */
+    assertEquals(42, NullableVariableQuery(42).param)
+    assertEquals(null, NullableVariableQuery(null).param)
+  }
+
+  @Test
+  fun nullableVariableWithOptionalDirectivesGeneratesOptional() {
+    /**
+     * If the user opted-in @optional, it's possible to omit the variable again
+     */
+    assertEquals(Optional.Absent, NullableVariableWithOptionalDirectiveQuery().param)
+    assertEquals(Optional.Present(42), NullableVariableWithOptionalDirectiveQuery(Optional.Present(42)).param)
+    assertEquals(Optional.Present(null), NullableVariableWithOptionalDirectiveQuery(Optional.Present(null)).param)
+  }
+
+  @Test
+  fun nullableVariableWithDefaultValueGeneratesAbsentInKotlin() {
+    /**
+     * If the variable has a default value, it always get generated as Optional
+     */
+    assertEquals(Optional.Absent, NullableVariableWithDefaultValueQuery().param)
+    assertEquals(Optional.Present(42), NullableVariableWithDefaultValueQuery(Optional.Present(42)).param)
+    // Because the variable is nullable, it is possible to send null
+    assertEquals(Optional.Present(null), NullableVariableWithDefaultValueQuery(Optional.Present(null)).param)
+  }
+
+  @Test
+  fun nonnullVariableWithDefaultValueGeneratesAbsentInKotlin() {
+    /**
+     * If the variable has a default value, it always gets generated as Optional
+     */
+    assertEquals(Optional.Absent, NonNullVariableWithDefaultValueQuery().param)
+    assertEquals(Optional.Present(42), NonNullVariableWithDefaultValueQuery(Optional.Present(42)).param)
+    // Because the variable is nonnull, we cannot send null
+  }
+}

composite/tests/integration-tests-kotlin/src/commonTest/kotlin/test/variables/graphql/operations.graphql

@@ -0,0 +1,19 @@
+query NullableVariable($param: Int) {
+  fieldWithNullableParameter(param: $param)
+}
+
+query NullableVariableWithOptionalDirective($param: Int @optional) {
+  fieldWithNullableParameter(param: $param)
+}
+
+query NonNullVariable($param: Int!) {
+  fieldWithNullableParameter(param: $param)
+}
+
+query NullableVariableWithDefaultValue($param: Int = 42) {
+  fieldWithNullableParameter(param: $param)
+}
+
+query NonNullVariableWithDefaultValue($param: Int! = 42) {
+  fieldWithNullableParameter(param: $param)
+}

composite/tests/integration-tests-kotlin/src/commonTest/kotlin/test/variables/graphql/schema.graphqls

@@ -0,0 +1,4 @@
+type Query {
+  fieldWithNullableParameter(param: Int): Int
+  fieldWithNonNullParameter(param: Int!): Int
+}