Cannot import decorators-legacy in V7

[w0rldart]

Issue Creation Checklist

• [x] I understand that my issue will be automatically closed if I don't fill in the requested information
• [x] I have read the contribution guidelines

Bug Description

The documentation explicitly indicates to use decorators to define all aspects related to a model. From types, to relationships, and more.

However, I personally cannot get it to work, due to this issue in my VSCode editor

Cannot find module '@sequelize/core/decorators-legacy' or its corresponding type declarations.ts(2307)

Reproducible Example

• I use TypeScript
• Everything works fine without importing or trying to use decorators. I.e.:

import { Model, DataTypes, InferAttributes, InferCreationAttributes, CreationOptional } from '@sequelize/core'
import { RequestType } from '../types'
import { sequelize } from '../db'

class Request extends Model<InferAttributes<Request>, InferCreationAttributes<Request>> {
  declare id: CreationOptional<number>
  declare requestType: string
  declare requestData: object
  declare requester: string
  declare createdAt: CreationOptional<Date>
  declare updatedAt: CreationOptional<Date>
}

Request.init({
  id: {
    type: DataTypes.INTEGER,
    primaryKey: true,
    autoIncrement: true
  },
  requestType: {
    type: DataTypes.ENUM(
      RequestType.EXPENV_AZURE,
      RequestType.EXPENV_GCP,
      RequestType.VM_AZURE,
      RequestType.VM_GCP,
      RequestType.RPA_AZURE,
      RequestType.RPA_GCP,
      RequestType.AZURE_RG
    ),
    allowNull: true
  },
  requestData: {
    type: DataTypes.JSON,
    allowNull: false
  },
  requester: {
    type: DataTypes.STRING,
    allowNull: false
  },
  createdAt: {
    type: DataTypes.DATE
  },
  updatedAt: {
    type: DataTypes.DATE
  }
}, { sequelize })

• The sequelize directory inside node_modules seems to have all the requested data

However, and as per a standard example on this page, the usual flow to use decorators

import { Model, DataTypes, InferAttributes, InferCreationAttributes, CreationOptional, NonAttribute } from '@sequelize/core'
import { PrimaryKey, Attribute, AutoIncrement, NotNull, HasMany, BelongsTo } from '@sequelize/core/decorators-legacy'

has the second line, no matter what else I have in my file, always throw this error: Cannot find module '@sequelize/core/decorators-legacy' or its corresponding type declarations.ts(2307)

What do you expect to happen?

Find the module and not throw that error

What is actually happening?

Environment

• Sequelize version:

$ npm list @sequelize/core
[email protected] 
└── @sequelize/[email protected]

• Node.js version:

$ node -v
v18.12.1

• If TypeScript related: TypeScript version:

npm list typescript
[email protected]
├─┬ [email protected]
│ └── [email protected]
└─┬ [email protected]
  ├─┬ @typescript-eslint/[email protected]
  │ └─┬ [email protected]
  │   └── [email protected] deduped
  ├─┬ [email protected]
  │ └── [email protected] deduped
  └── [email protected] deduped

• tsconfig.json

{
  "compilerOptions": {
    "allowJs": false,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "module": "commonjs",
    "moduleResolution": "node",
    "outDir": "dist",
    "rootDir": ".",
    "skipLibCheck": true,
    "sourceMap": true,
    "strict": true,
    "strictNullChecks": true,
    "target": "es6",
    "types": ["node"],
  },
}

• Database & Version: MySQL 8
• Connector library & Version: [email protected]

Would you be willing to resolve this issue by submitting a Pull Request?

• [ ] Yes, I have the time and I know how to start.
• [x] Yes, I have the time but I will need guidance.
• [ ] No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• [ ] No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

---

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[ephys]

You need to set your tsconfig moduleResolution option to node16 or nodenext: https://www.typescriptlang.org/docs/handbook/esm-node.html#packagejson-exports-imports-and-self-referencing

[w0rldart]

Thank you ephys for the reply. I will try it, but it doesn't make sense. Your own tsconfig has moduleResolution set just to node, like I do

If this turns out to be the issue, may I suggest that this is clearly reflected somewhere in the documentation?

[ephys]

Our own tsconfig should not be used as an example, it's overly complicated because we try to support multiple versions of TypeScript

I've converted this to a documentation issue

[w0rldart]

Our own tsconfig should not be used as an example, it's overly complicated because we try to support multiple versions of TypeScript

I've converted this to a documentation issue

It would be handy to have an example tsconfig.json that's suitable to use in a fresh V7 project

[Lordfirespeed]

This is pretty awful, I can't lie. NodeNext is practically unusable due to

• lack of (good) documentation/examples
• Impenetrable path aliasing (I vehemently reject ../../, that is an abomination)

The exports block is a lovely QoL feature when you're on NodeNext, but NodeNext being required to use v7 at all? :weary:

[ephys]

You can have path aliasing in your own project by configuring exports in your own package.json

The explanation for the different type of moduleResolutions is described here: https://www.typescriptlang.org/tsconfig#moduleResolution If that is not sufficient, I would recommend opening an issue on the TypeScript repo about it instead

You don't technically have to use Node16/NodeNext/Bundler (though I don't see why you wouldn't use the ts module resolution that accurately replicates how node resolves modules if you're using node). You can configure paths, or use resolvePackageJsonExports instead

[Lordfirespeed]

yeah, sorry. Was very frustrated last night. Turned out my path aliasing was working just fine but needed the .js extensions - the error was incredibly vague ('cannot resolve...')

[WikiRik]

We have opened https://github.com/sequelize/website/pull/583 to document this. Are we missing anything?

[ephys]

As mentioned in https://github.com/sequelize/sequelize/issues/16866, we also need to update the SSCCE repo's tsconfig

[johneatmon]

FWIW, you can set moduleResolution to "Bundler" and it also works. (TS notes that "This is the recommended setting in TypeScript 5.0+ for applications that use a bundler.")

I have Sequelize v7 with decorators working in a Next.js 14 project, and I'm basically using the default create-t3-app tsconfig.json. Posting this here in case anyone needs a similar resolution:

{
  "compilerOptions": {
    /* Base Options */
    "esModuleInterop": true,
    "skipLibCheck": true,
    "target": "ES2022",
    "allowJs": true,
    "resolveJsonModule": true,
    "moduleDetection": "force",
    "isolatedModules": true,
    /* Sequelize */
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "allowImportingTsExtensions": true,
    /* Strictness */
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "forceConsistentCasingInFileNames": true,
    "checkJs": true,
    /* Bundled projects */
    "lib": ["dom", "dom.iterable", "ES2022"],
    "noEmit": true,
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "jsx": "preserve",
    "plugins": [{ "name": "next" }],
    "incremental": true,
    /* Path aliases */
    "baseUrl": ".",
    "paths": {
      "@/*": ["./*"]
    },
    /* Needed for ts-node */
    "typeRoots": ["**/*.d.ts"]
  },
  "include": [
    ".eslintrc.cjs",
    "next-env.d.ts",
    "**/*.ts",
    "**/*.tsx",
    "**/*.cjs",
    "**/*.js",
    ".next/types/**/*.ts"
  ],
  "exclude": ["node_modules"],
  "ts-node": {
    "esm": true
  }
}