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how to exclude null from @IsOptional #686

@horrendo

Description

@horrendo

I'm trying to validate a field which can be missing (or undefined), but if present, cannot be null. Currently it seems that if I have the @IsOptional() decorator and the value is null, it bypasses any further validation.

I tried making my own decorator similar to @IsOptional() but got a runtime error:

Error: Cannot find module 'class-validator/types/metadata/ValidationMetadata'
Require stack:
{my modules}
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:965:15)
    at Function.Module._resolveFilename (/Users/stbaldwin/git/unsullied/node_modules/tsconfig-paths/lib/register.js:75:40)
    at Function.Module._load (internal/modules/cjs/loader.js:841:27)
    at Module.require (internal/modules/cjs/loader.js:1025:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at Object.<anonymous> (/Users/stbaldwin/git/unsullied/src/utils/validation/OptionalButNotNull.ts:3:1)
    at Module._compile (internal/modules/cjs/loader.js:1137:30)
    at Module.m._compile (/Users/stbaldwin/git/unsullied/node_modules/ts-node/src/index.ts:837:23)
    at Module._extensions..js (internal/modules/cjs/loader.js:1157:10)
    at Object.require.extensions.<computed> [as .ts] (/Users/stbaldwin/git/unsullied/node_modules/ts-node/src/index.ts:840:12)

Here is my decorator:

import { ValidationOptions, ValidationTypes, getMetadataStorage } from 'class-validator';
import { ValidationMetadataArgs } from 'class-validator/types/metadata/ValidationMetadataArgs';
import { ValidationMetadata } from 'class-validator/types/metadata/ValidationMetadata';
/**
 * Checks if value is missing and if so, ignores all validators.
 */
export function IsOptionalButNotNull(validationOptions?: ValidationOptions): PropertyDecorator {
    return function (object: object, propertyName: string | symbol): void {
        const args: ValidationMetadataArgs = {
            type: ValidationTypes.CONDITIONAL_VALIDATION,
            target: object.constructor,
            propertyName: String(propertyName),
            constraints: [
                (object: any, _value: any): boolean => {
                    return object[propertyName] !== undefined;
                }
            ],
            validationOptions: validationOptions
        };
        getMetadataStorage().addValidationMetadata(new ValidationMetadata(args));
    };
}

Is there another solution?

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