feat: add @type? optional notation

src/csv-loader/loader.ts

@@ -82,7 +82,11 @@ function resolveReferenceId(
 }
 
 function parseReferenceIds(schema: ReferenceSchema, valueString: string): unknown {
-  const valueParser = new ReferenceValueParser(valueString.trim());
+  const trimmed = valueString.trim();
+  if (schema.isOptional && trimmed === '') {
+    return null;
+  }
+  const valueParser = new ReferenceValueParser(trimmed);
   const ids = valueParser.parseIds(schema.isArray);
   if (schema.isArray) {
     return ids;
@@ -136,6 +140,7 @@ function parseValueWithReferenceIds(
 function extractNestedReferenceIds(value: unknown, schema: Schema): unknown {
   switch (schema.type) {
     case 'reference':
+      if (value === null || value === undefined) return value;
       if (schema.isArray) {
         const ids = Array.isArray(value) ? value : [value];
         return ids.map(id => String(id));
@@ -258,6 +263,7 @@ function resolveNestedReferences(
 ): unknown {
   switch (schema.type) {
     case 'reference': {
+      if (value === null || value === undefined) return value;
       const { lookup } = loadReferenceTable(schema, refBaseDir, defaultPrimaryKey, currentFilePath);
       if (schema.isArray) {
         const ids = Array.isArray(value) ? value : [value];
@@ -379,9 +385,14 @@ function parseReferenceValue(
   defaultPrimaryKey: string,
   currentFilePath: string | undefined
 ): unknown {
+  const trimmed = valueString.trim();
+  if (schema.isOptional && trimmed === '') {
+    return null;
+  }
+
   const { lookup } = loadReferenceTable(schema, refBaseDir, defaultPrimaryKey, currentFilePath);
   
-  const valueParser = new ReferenceValueParser(valueString.trim());
+  const valueParser = new ReferenceValueParser(trimmed);
   const ids = valueParser.parseIds(schema.isArray);
   
   if (schema.isArray) {
@@ -497,10 +508,10 @@ function schemaToTypeString(schema: Schema, resourceNames?: Map<string, string>)
     case 'union':
       return schema.members.map(m => schemaToTypeString(m, resourceNames)).join(' | ');
     case 'reference': {
-      // Use the resource name mapping if provided, otherwise capitalize table name
       const typeName = resourceNames?.get(schema.tableName) ||
         schema.tableName.charAt(0).toUpperCase() + schema.tableName.slice(1);
-      return schema.isArray ? `readonly ${typeName}[]` : typeName;
+      const baseType = schema.isArray ? `readonly ${typeName}[]` : typeName;
+      return schema.isOptional ? `${baseType} | null` : baseType;
     }
     case 'array':
       if (schema.element.type === 'tuple') {
@@ -764,6 +775,12 @@ function generateSchemaResolutionCode(
   switch (schema.type) {
     case 'reference': {
       const lookup = lookupVar(schema.tableName);
+      if (schema.isOptional) {
+        if (schema.isArray) {
+          return `(${valueExpr} === null || ${valueExpr} === undefined ? ${valueExpr} : (Array.isArray(${valueExpr}) ? ${valueExpr}.map(id => ${lookup}.get(String(id))) : ${lookup}.get(String(${valueExpr}))))`;
+        }
+        return `(${valueExpr} === null || ${valueExpr} === undefined ? ${valueExpr} : ${lookup}.get(String(${valueExpr})))`;
+      }
       if (schema.isArray) {
         return `(Array.isArray(${valueExpr}) ? ${valueExpr}.map(id => ${lookup}.get(String(id))) : ${valueExpr})`;
       }