In the case of working with Sanity TypeGen, it can create Types for Sanity Studio schema types and GROQ query results. So, as you build out your front end, you only access values within documents that exist, as well as defensively code against values that could be null.

Sanity TypeGen will create Types for queries that are assigned to a variable and use the defineQuery function.

You're able to use the Sanity CLI from inside the Next.js application because of the sanity.cli.ts file at the root of your project.

npx sanity@latest schema extract --path=./src/sanity/extract.json

The --path argument is provided so the schema file is written to the same folder as all our other Sanity utilities.

You should see a response like the one below and a newly generated schema.json file in your src/sanity directory

✅ Extracted schema

This file contains all the details about your Sanity Studio schema types, which TypeGen will need to create types from.

By default, TypeGen will create a file for types at the project's root. Again, to keep Sanity-specific files colocated, we can preconfigure some defaults and keep the project root tidy.

{
  "path": "./src/**/*.{ts,tsx,js,jsx}",
  "schema": "./src/sanity/extract.json",
  "generates": "./src/sanity/types.ts"
}

The configuration here will:

1. Scan the src directory for GROQ queries to create Types.
2. Additionally, use the extract.json file created during the previous task.
3. Write a new types.ts file with our other Sanity utilities.

npx sanity@latest typegen generate

You should see a response like the one below and a newly created src/sanity/types.ts file in your project.

✅ Generated TypeScript types for 15 schema types and 2 GROQ queries in 1 files into: ./src/sanity/types.ts

Success! You now have Types for your Sanity Studio schema types and GROQ queries.

The extract.json file will need to be updated every time you update your Sanity Studio schema types and TypeGen every time you do or update your GROQ queries.

Instead of doing these steps separately, you can include scripts in your package.json file to make running these automatic and more convenient.

"scripts": {
  // ...all your other scripts
  "predev": "npm run typegen",
  "prebuild": "npm run typegen",
  "typegen": "sanity schema extract --path=./src/sanity/extract.json && sanity typegen generate"
},

You can now run both the schema extraction and TypeGen commands with one line:

npm run typegen

You now have all the tools and configurations to author and query Sanity content with a Type-safe, excellent developer experience. Now it's finally time to query and display Sanity content.