From dacdbae4e3dbc5a8de2f39f13f5db456ed0d18b3 Mon Sep 17 00:00:00 2001
From: Nabil Abdel-Hafeez <7283535+987Nabil@users.noreply.github.com>
Date: Sun, 30 Jun 2024 23:24:51 +0200
Subject: [PATCH] Failing deriving Schemas with transient fields without
 defaults (#654)

---
 .../src/main/scala-2/zio/schema/DeriveSchema.scala | 14 +++++++++++---
 .../src/main/scala-3/zio/schema/DeriveSchema.scala |  4 ++++
 .../scala-2/zio/schema/codec/JsonCodecSpec.scala   |  2 +-
 .../scala-2/zio/schema/codec/ThriftCodecSpec.scala |  2 +-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/zio-schema-derivation/shared/src/main/scala-2/zio/schema/DeriveSchema.scala b/zio-schema-derivation/shared/src/main/scala-2/zio/schema/DeriveSchema.scala
index 018079141..9d5d070e4 100644
--- a/zio-schema-derivation/shared/src/main/scala-2/zio/schema/DeriveSchema.scala
+++ b/zio-schema-derivation/shared/src/main/scala-2/zio/schema/DeriveSchema.scala
@@ -271,10 +271,18 @@ object DeriveSchema {
                 }
                 val hasDefaultAnnotation =
                   annotations.exists {
-                    case q"new _root_.zio.schema.annotation.fieldDefaultValue(..$_)" => true
-                    case _                                                           => false
+                    case ann if ann.toString.contains("new fieldDefaultValue") => true
+                    case _                                                     => false
                   }
-                if (hasDefaultAnnotation || defaultConstructorValues.get(i).isEmpty) {
+                val transientField =
+                  annotations.exists {
+                    case ann if ann.toString().endsWith("new transientField()") => true
+                    case _                                                      => false
+                  }
+                if (transientField && !(hasDefaultAnnotation || defaultConstructorValues.contains(i))) {
+                  throw new IllegalStateException(s"Field ${symbol.name} is transient and must have a default value.")
+                }
+                if (hasDefaultAnnotation || !defaultConstructorValues.contains(i)) {
                   annotations
                 } else {
                   annotations :+
diff --git a/zio-schema-derivation/shared/src/main/scala-3/zio/schema/DeriveSchema.scala b/zio-schema-derivation/shared/src/main/scala-3/zio/schema/DeriveSchema.scala
index 57df11ebc..e012fbac0 100644
--- a/zio-schema-derivation/shared/src/main/scala-3/zio/schema/DeriveSchema.scala
+++ b/zio-schema-derivation/shared/src/main/scala-3/zio/schema/DeriveSchema.scala
@@ -339,6 +339,10 @@ private case class DeriveSchema()(using val ctx: Quotes) {
             .map(_.asExpr.asInstanceOf[Expr[Any]])
           val hasDefaultAnnotation =
             field.annotations.exists(_.tpe <:< TypeRepr.of[zio.schema.annotation.fieldDefaultValue[_]])
+          val transientField = field.annotations.exists(_.tpe <:< TypeRepr.of[zio.schema.annotation.transientField])
+          if (transientField && !hasDefaultAnnotation && defaults.get(field.name).isEmpty) {
+            report.errorAndAbort(s"Field ${field.name} is transient and must have a default value.")
+          }
           if (hasDefaultAnnotation || defaults.get(field.name).isEmpty) {
             annos
           } else {
diff --git a/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala b/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala
index 115bee8e5..a74fb7e27 100644
--- a/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala
+++ b/zio-schema-json/shared/src/test/scala-2/zio/schema/codec/JsonCodecSpec.scala
@@ -1629,7 +1629,7 @@ object JsonCodecSpec extends ZIOSpecDefault {
     query: String,
     pageNumber: Int,
     resultPerPage: Int,
-    @transientField nextPage: String
+    @transientField nextPage: String = ""
   )
 
   val searchRequestWithTransientFieldSchema: Schema[SearchRequestWithTransientField] =
diff --git a/zio-schema-thrift/src/test/scala-2/zio/schema/codec/ThriftCodecSpec.scala b/zio-schema-thrift/src/test/scala-2/zio/schema/codec/ThriftCodecSpec.scala
index 5f21af2ca..5067e24f4 100644
--- a/zio-schema-thrift/src/test/scala-2/zio/schema/codec/ThriftCodecSpec.scala
+++ b/zio-schema-thrift/src/test/scala-2/zio/schema/codec/ThriftCodecSpec.scala
@@ -1169,7 +1169,7 @@ object ThriftCodecSpec extends ZIOSpecDefault {
     implicit val schema: Schema[PersonWithOptionalField] = DeriveSchema.gen[PersonWithOptionalField]
   }
 
-  case class PersonWithTransientField(name: String, @transientField age: Int)
+  case class PersonWithTransientField(name: String, @transientField age: Int = 0)
 
   object PersonWithTransientField {
     implicit val schema: Schema[PersonWithTransientField] = DeriveSchema.gen[PersonWithTransientField]