Fixing class-validator issues in a new Nest js project

PublishedApril 5, 2020

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Nest: No metadata found. There is more than once class-validator version installed probably. You need to flatten your dependencies.

This one made me crazy. Should I install class-validator as a peer dependency ? Is it a problem in the yarn.lock or in package.json ?

Not at all ! It turned out that my DTO had zero validation rules !

It's that simple : if you get a

No metadata found. There is more than once class-validator version installed probably. You need to flatten your dependencies.

when using ValidationPipe, triple-check that you have at least one validation rule.

For example:

import { IsNotEmpty } from "class-validator"; export class CreateUserDto { @IsNotEmpty() firstName: string; lastName: string; }

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The "class-validator" package is missing. Please, make sure to install this library ($ npm install class-validator) to take advantage of ValidationPipe.

Nest: No metadata found. There is more than once class-validator version installed probably. You need to flatten your dependencies.