EPIC: re-design of db seed feature

[Jolg42]

prisma db seed is currently a Preview feature.

During this phase, we noticed different issues caused by the complexity of the current implementation.

The Migrations Team decided to remove the complexity and make it a lot easier to understand for users and to maintain.

The new implementation is in #8146

How it will work is that a prisma.seed property in the package.json of your project will be required if you want to use prisma db seed.

The CLI will give examples that can be copy-pasted.

If you are currently using the previous implementation of prisma db seed and upgrade to this new version then it will throw an error with an upgrade help message which should be easy to fix (add prisma.seed to the package.json)

package.json example for a JavaScript project

  "prisma": {
    "seed": "node prisma/seed.js"
  } 

package.json example for a TypeScript project

  "prisma": {
    "seed": "ts-node prisma/seed.ts"
  }

Example of a prisma/seed.js

async function main() {
  await new Promise((resolve) => setTimeout(resolve, 100))
  console.log('Hello from seed.js')
}

main()
  .then(() => console.log('Goodbye from seed.js'))
  .catch((e) => {
    console.error(e)
    process.exit(1)
  })

What needs to done for releasing the "new" db seed:

• Review and merge fix(db seed): redesign of db seed #8146
• QA db seed
• Update docs db seed GA docs#2161
• db seed tests need to run on multiple platforms, not just Ubuntu #8033
• e2e Test seeding ecosystem-tests#1806
• Update Preview feature feedback: Integrated seeding  #5161
• Close issues and let users know that they can use the new version https://github.com/prisma/prisma/issues?q=is%3Aissue+label%3A%22topic%3A+db+seed%22+is%3Aopen

[Jolg42]

It's possible to try it out with a specific version of the Prisma CLI like this:

npm install -D prisma@2.30.0-integration-db-seed-new-behavior.1

# Then run 
prisma db seed --preview-feature

# db seed is also integrated in
prisma migrate reset
prisma migrate dev

Or by using npx with the specific version:

npx prisma@2.30.0-integration-db-seed-new-behavior.1 db seed --preview-feature

[jasonkuhrt]

Note this will work and is cleaner IMO:

"prisma": {
    "seed": "ts-node prisma/seed"
  }

[tobiasdiez]

May I suggest that the error handling part (copied from the above example)

main()
  .then(() => console.log('Goodbye from seed.js'))
  .catch((e) => {
    console.error(e)
    process.exit(1)
  })

may be moved to Prisma's cli code, i.e one only exports the main method and prisma takes care of the invocation. The main reason is that sometimes you do not want to exit in case there is an error during seeding. For example, if one uses generate --watch or jest --watch using seed to initialize tests. In the former case you prefer to be notified about the error, and in the latter the test should fail -- however, you don't really want to exit the calling process.

[Jolg42]

Hi @tobiasdiez indeed, exiting is not the best in some cases. This is just an example and in this implementation you are free to change it as you need.
We removed the "magic" around export and invocation to simplify but that also means you can write a small layer that does that in your project.

[Jolg42]

Closing, rest is tracked in #8628

I'll create an issue to have better suggestion for ESM module projects help output.