fix(codegen): make startCursor and endCursor optional, as the edges may be empty

Author: WipeAir

graphql-kotlin-toolkit-codegen/src/main/kotlin/com/auritylab/graphql/kotlin/toolkit/codegen/generator/fieldResolver/PaginationFieldResolverGenerator.kt

@@ -88,12 +88,18 @@ internal class PaginationFieldResolverGenerator(
                 )
                 getFunSpec.addStatement("val result = resolve(${resolveArgs}env = internalEnv)")
 
-                getFunSpec.addStatement("val edges = result.data.map { %T(it, resolveCursor(it, internalEnv)) }", generatedMapper.getPaginationEdgeClassName())
                 getFunSpec.addStatement(
-                    "val pageInfo = %T(result.hasNextPage, result.hasPreviousPage, edges.first().cursor, edges.last().cursor)",
+                    "val edges = result.data.map { %T(it, resolveCursor(it, internalEnv)) }",
+                    generatedMapper.getPaginationEdgeClassName()
+                )
+                getFunSpec.addStatement(
+                    "val pageInfo = %T(result.hasNextPage, result.hasPreviousPage, edges.firstOrNull()?.cursor, edges.lastOrNull()?.cursor)",
                     generatedMapper.getPaginationPageInfoClassName()
                 )
-                getFunSpec.addStatement("return %T(edges, pageInfo)", generatedMapper.getPaginationConnectionClassName())
+                getFunSpec.addStatement(
+                    "return %T(edges, pageInfo)",
+                    generatedMapper.getPaginationConnectionClassName()
+                )
             }
             .build())
     }

graphql-kotlin-toolkit-codegen/src/main/kotlin/com/auritylab/graphql/kotlin/toolkit/codegen/generator/pagination/PaginationPageInfoGenerator.kt

@@ -20,7 +20,7 @@ internal class PaginationPageInfoGenerator(
     override val dataProperties: List<DataProperty> = listOf(
         DataProperty("hasNextPage", GraphQLNonNull(Scalars.GraphQLBoolean)),
         DataProperty("hasPreviousPage", GraphQLNonNull(Scalars.GraphQLBoolean)),
-        DataProperty("startCursor", GraphQLNonNull(Scalars.GraphQLString)),
-        DataProperty("endCursor", GraphQLNonNull(Scalars.GraphQLString))
+        DataProperty("startCursor", Scalars.GraphQLString),
+        DataProperty("endCursor", Scalars.GraphQLString)
     )
 }