fix(typescript): generate non-nullable json columns as NonNullable<Json>

src/server/templates/typescript.ts

@@ -483,6 +483,11 @@ export const apply = async ({
     : ''
 
   function generateNullableUnionTsType(tsType: string, isNullable: boolean) {
+    // The Json type already includes `null`, so a NOT NULL json/jsonb column has to be
+    // narrowed with NonNullable to reflect the database constraint. See supabase/postgres-meta#1055.
+    if (tsType === 'Json' && !isNullable) {
+      return `NonNullable<${tsType}>`
+    }
     // Only add the null union if the type is not unknown as unknown already includes null
     if (tsType === 'unknown' || tsType === 'any' || !isNullable) {
       return tsType

test/server/typegen.ts

@@ -6964,3 +6964,46 @@ test('typegen: python w/ excluded/included schemas', async () => {
     })
   }
 })
+
+test('typegen: typescript w/ NOT NULL json column narrows Json to NonNullable<Json>', async () => {
+  // The generated Json type includes `null`, so a NOT NULL json/jsonb column has to be
+  // narrowed with NonNullable to honor the database constraint. A nullable json column is
+  // left as-is because Json already covers null. See supabase/postgres-meta#1055.
+  await app.inject({
+    method: 'POST',
+    path: '/query',
+    payload: {
+      query: `
+        CREATE SCHEMA IF NOT EXISTS json_nullability_test;
+        CREATE TABLE IF NOT EXISTS json_nullability_test.documents (
+          id serial PRIMARY KEY,
+          required_metadata jsonb NOT NULL,
+          optional_metadata jsonb
+        );
+      `,
+    },
+  })
+
+  try {
+    const { body } = await app.inject({
+      method: 'GET',
+      path: '/generators/typescript',
+      query: { included_schemas: 'json_nullability_test' },
+    })
+    // NOT NULL jsonb narrows to NonNullable<Json> (Row and Insert).
+    expect(body).toContain('required_metadata: NonNullable<Json>')
+    expect(body).not.toContain('required_metadata: Json | null')
+    // Nullable jsonb is unchanged: Json already includes null.
+    expect(body).toContain('optional_metadata: Json | null')
+  } finally {
+    await app.inject({
+      method: 'POST',
+      path: '/query',
+      payload: {
+        query: `
+          DROP SCHEMA IF EXISTS json_nullability_test CASCADE;
+        `,
+      },
+    })
+  }
+})