From fda68917d174ed1682cb87f83ceca08ded7a931c Mon Sep 17 00:00:00 2001
From: Jiefan Li <jiefli@linkedin.com>
Date: Tue, 17 Jan 2023 12:58:36 -0800
Subject: [PATCH] Coral-Schema: return nullable schema for array item and map
 value (#345)

---
 .../linkedin/coral/schema/avro/ToNullableSchemaVisitor.java | 4 ++--
 .../src/test/resources/testToNullableSchema-expected.avsc   | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/coral-schema/src/main/java/com/linkedin/coral/schema/avro/ToNullableSchemaVisitor.java b/coral-schema/src/main/java/com/linkedin/coral/schema/avro/ToNullableSchemaVisitor.java
index a8247b532..2a04cccd6 100644
--- a/coral-schema/src/main/java/com/linkedin/coral/schema/avro/ToNullableSchemaVisitor.java
+++ b/coral-schema/src/main/java/com/linkedin/coral/schema/avro/ToNullableSchemaVisitor.java
@@ -46,12 +46,12 @@ public Schema union(Schema union, List<Schema> options) {
 
   @Override
   public Schema array(Schema array, Schema element) {
-    return Schema.createArray(element);
+    return Schema.createArray(SchemaUtilities.makeNullable(element, false));
   }
 
   @Override
   public Schema map(Schema map, Schema value) {
-    return Schema.createMap(value);
+    return Schema.createMap(SchemaUtilities.makeNullable(value, false));
   }
 
   @Override
diff --git a/coral-schema/src/test/resources/testToNullableSchema-expected.avsc b/coral-schema/src/test/resources/testToNullableSchema-expected.avsc
index 9bec8232e..c79b02be6 100644
--- a/coral-schema/src/test/resources/testToNullableSchema-expected.avsc
+++ b/coral-schema/src/test/resources/testToNullableSchema-expected.avsc
@@ -18,14 +18,14 @@
     "name" : "Array_Col",
     "type" : [ "null", {
       "type" : "array",
-      "items" : "string"
+      "items" : [ "null", "string" ]
     } ],
     "default" : null
   }, {
     "name" : "Map_Col",
     "type" : [ "null", {
       "type" : "map",
-      "values" : "string"
+      "values" : [ "null", "string" ]
     } ],
     "default" : null
   }, {
@@ -86,7 +86,7 @@
         "name" : "Map_Col",
         "type" : [ "null", {
           "type" : "map",
-          "values" : "string"
+          "values" : [ "null", "string" ]
         } ],
         "default" : null
       } ]