fix(csv-to-pg): emit empty array '{}' instead of NULL for array types

packages/csv-to-pg/__tests__/__snapshots__/export.test.ts.snap

@@ -8,6 +8,16 @@ exports[`test case arrays 1`] = `
   ('450e3b3b-b68d-4abc-990c-65cb8a1dcdb4', '{a,b}');"
 `;
 
+exports[`test case empty array fields emit empty array literal 1`] = `
+"INSERT INTO metaschema_modules_public.secure_table_provision (
+  id,
+  node_type,
+  fields,
+  grant_roles
+) VALUES
+  ('450e3b3b-b68d-4abc-990c-65cb8a1dcdb4', 'DataTimestamps', '{}', '{}');"
+`;
+
 exports[`test case image/attachment 1`] = `
 "INSERT INTO metaschema_public.field (
   id,
@@ -61,6 +71,17 @@ exports[`test case jsonb/json 1`] = `
   ('450e3b3b-b68d-4abc-990c-65cb8a1dcdb4', 'name here', '{"a":1}');"
 `;
 
+exports[`test case null array fields emit empty array literal instead of NULL 1`] = `
+"INSERT INTO metaschema_modules_public.secure_table_provision (
+  id,
+  node_type,
+  fields,
+  grant_privileges,
+  out_fields
+) VALUES
+  ('450e3b3b-b68d-4abc-990c-65cb8a1dcdb4', 'DataTimestamps', '{}', '{}', '{}');"
+`;
+
 exports[`test case test case 1`] = `Promise {}`;
 
 exports[`test case test case parser 1`] = `

packages/csv-to-pg/__tests__/export.test.ts

@@ -220,6 +220,64 @@ it('interval type', async () => {
   expect(sql).toMatchSnapshot();
 });
 
+it('null array fields emit empty array literal instead of NULL', async () => {
+  const parser = new Parser({
+    schema: 'metaschema_modules_public',
+    singleStmts: true,
+    table: 'secure_table_provision',
+    fields: {
+      id: 'uuid',
+      node_type: 'text',
+      fields: 'jsonb[]',
+      grant_privileges: 'jsonb[]',
+      out_fields: 'uuid[]'
+    }
+  });
+
+  const sql = await parser.parse([
+    {
+      id: '450e3b3b-b68d-4abc-990c-65cb8a1dcdb4',
+      node_type: 'DataTimestamps',
+      fields: null,
+      grant_privileges: null,
+      out_fields: null
+    }
+  ]);
+
+  // Should emit '{}' for array columns instead of NULL
+  expect(sql).toContain("'{}'");
+  expect(sql).not.toContain('NULL');
+  expect(sql).toMatchSnapshot();
+});
+
+it('empty array fields emit empty array literal', async () => {
+  const parser = new Parser({
+    schema: 'metaschema_modules_public',
+    singleStmts: true,
+    table: 'secure_table_provision',
+    fields: {
+      id: 'uuid',
+      node_type: 'text',
+      fields: 'jsonb[]',
+      grant_roles: 'text[]'
+    }
+  });
+
+  const sql = await parser.parse([
+    {
+      id: '450e3b3b-b68d-4abc-990c-65cb8a1dcdb4',
+      node_type: 'DataTimestamps',
+      fields: [],
+      grant_roles: []
+    }
+  ]);
+
+  // Empty arrays should also emit '{}' not NULL
+  expect(sql).toContain("'{}'");
+  expect(sql).not.toContain('NULL');
+  expect(sql).toMatchSnapshot();
+});
+
 it('interval type with string value', async () => {
   const parser = new Parser({
     schema: 'metaschema_modules_public',

packages/csv-to-pg/src/parse.ts

@@ -104,9 +104,13 @@ const escapeArrayElement = (value: unknown): string => {
 
 /**
  * Convert an array to PostgreSQL array literal format with proper escaping.
+ * Returns '{}' for empty arrays instead of undefined.
  */
 const psqlArray = (value: unknown): string | undefined => {
-  if (Array.isArray(value) && value.length) {
+  if (Array.isArray(value)) {
+    if (value.length === 0) {
+      return '{}';
+    }
     return `{${value.map(escapeArrayElement).join(',')}}`;
   }
   return undefined;
@@ -213,12 +217,23 @@ export class ValidationError extends Error {
 type CoercionFunc = (record: Record<string, unknown>) => Node;
 
 /**
- * Helper to create a NULL node or throw if field is required
+ * Check if a type is an array type (e.g. 'text[]', 'uuid[]', 'jsonb[]')
+ */
+const isArrayType = (type: string): boolean => type.endsWith('[]');
+
+/**
+ * Helper to create a NULL node or throw if field is required.
+ * For array types, emits an empty array literal '{}' instead of NULL.
  */
 const makeNullOrThrow = (fieldName: string, rawValue: unknown, type: string, required: boolean, reason: string): Node => {
   if (required) {
     throw new ValidationError(fieldName, rawValue, type, reason);
   }
+  if (isArrayType(type)) {
+    return nodes.aConst({
+      sval: ast.string({ sval: '{}' })
+    });
+  }
   return nodes.aConst({ isnull: true });
 };