Handle const enums in schema type resolution

Author: smorimoto

src/schema-parser/base-schema-parsers/enum.ts

@@ -158,7 +158,7 @@ export class EnumSchemaParser extends MonoSchemaParser {
   }
 
   formatEnumKey = ({ key, value }) => {
-    let formatted;
+    let formatted: string | undefined;
 
     if (key) {
       formatted = this.typeNameFormatter.format(key, {

src/schema-parser/schema-utils.ts

@@ -266,9 +266,9 @@ export class SchemaUtils {
       );
     }
 
-    let resultType;
+    let resultType: string;
 
-    if (this.isConstantSchema(schema)) {
+    if (this.isConstantSchema(schema) && !schema.enum) {
       resultType = this.formatJsValue(schema.const);
     } else {
       const primitiveType = this.getSchemaPrimitiveType(schema);