/
reflector.service.ts
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/
reflector.service.ts
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import { CustomDecorator, SetMetadata, Type } from '@nestjs/common';
import { isEmpty, isObject } from '@nestjs/common/utils/shared.utils';
import { uid } from 'uid';
/**
* @publicApi
*/
export interface CreateDecoratorOptions<TParam = any, TTransformed = TParam> {
/**
* The key for the metadata.
* @default uid(21)
*/
key?: string;
/**
* The transform function to apply to the metadata value.
* @default value => value
*/
transform?: (value: TParam) => TTransformed;
}
type CreateDecoratorWithTransformOptions<
TParam,
TTransformed = TParam,
> = CreateDecoratorOptions<TParam, TTransformed> &
Required<Pick<CreateDecoratorOptions<TParam, TTransformed>, 'transform'>>;
/**
* @publicApi
*/
export type ReflectableDecorator<TParam, TTransformed = TParam> = ((
opts?: TParam,
) => CustomDecorator) & {
KEY: string;
};
/**
* Helper class providing Nest reflection capabilities.
*
* @see [Reflection](https://docs.nestjs.com/guards#putting-it-all-together)
*
* @publicApi
*/
export class Reflector {
/**
* Creates a decorator that can be used to decorate classes and methods with metadata.
* Can be used as a strongly-typed alternative to `@SetMetadata`.
* @param options Decorator options.
* @returns A decorator function.
*/
static createDecorator<TParam>(
options?: CreateDecoratorOptions<TParam>,
): ReflectableDecorator<TParam>;
static createDecorator<TParam, TTransformed>(
options: CreateDecoratorWithTransformOptions<TParam, TTransformed>,
): ReflectableDecorator<TParam, TTransformed>;
static createDecorator<TParam, TTransformed = TParam>(
options: CreateDecoratorOptions<TParam, TTransformed> = {},
): ReflectableDecorator<TParam, TTransformed> {
const metadataKey = options.key ?? uid(21);
const decoratorFn =
(metadataValue: TParam) =>
(target: object | Function, key?: string | symbol, descriptor?: any) => {
const value = options.transform
? options.transform(metadataValue)
: metadataValue;
SetMetadata(metadataKey, value ?? {})(target, key, descriptor);
};
decoratorFn.KEY = metadataKey;
return decoratorFn as ReflectableDecorator<TParam, TTransformed>;
}
/**
* Retrieve metadata for a reflectable decorator for a specified target.
*
* @example
* `const roles = this.reflector.get(Roles, context.getHandler());`
*
* @param decorator reflectable decorator created through `Reflector.createDecorator`
* @param target context (decorated object) to retrieve metadata from
*
*/
public get<T extends ReflectableDecorator<any>>(
decorator: T,
target: Type<any> | Function,
): T extends ReflectableDecorator<any, infer R> ? R : unknown;
/**
* Retrieve metadata for a specified key for a specified target.
*
* @example
* `const roles = this.reflector.get<string[]>('roles', context.getHandler());`
*
* @param metadataKey lookup key for metadata to retrieve
* @param target context (decorated object) to retrieve metadata from
*
*/
public get<TResult = any, TKey = any>(
metadataKey: TKey,
target: Type<any> | Function,
): TResult;
/**
* Retrieve metadata for a specified key or decorator for a specified target.
*
* @example
* `const roles = this.reflector.get<string[]>('roles', context.getHandler());`
*
* @param metadataKey lookup key or decorator for metadata to retrieve
* @param target context (decorated object) to retrieve metadata from
*
*/
public get<TResult = any, TKey = any>(
metadataKeyOrDecorator: TKey,
target: Type<any> | Function,
): TResult {
const metadataKey =
(metadataKeyOrDecorator as ReflectableDecorator<unknown>).KEY ??
metadataKeyOrDecorator;
return Reflect.getMetadata(metadataKey, target);
}
/**
* Retrieve metadata for a specified decorator for a specified set of targets.
*
* @param decorator lookup decorator for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAll<T extends ReflectableDecorator<any>>(
decorator: T,
targets: (Type<any> | Function)[],
): T extends ReflectableDecorator<infer R>
? R extends Array<any>
? R
: R[]
: unknown;
/**
* Retrieve metadata for a specified key for a specified set of targets.
*
* @param metadataKey lookup key for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAll<TResult extends any[] = any[], TKey = any>(
metadataKey: TKey,
targets: (Type<any> | Function)[],
): TResult;
/**
* Retrieve metadata for a specified key or decorator for a specified set of targets.
*
* @param metadataKeyOrDecorator lookup key or decorator for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAll<TResult extends any[] = any[], TKey = any>(
metadataKeyOrDecorator: TKey,
targets: (Type<any> | Function)[],
): TResult {
return (targets || []).map(target =>
this.get(metadataKeyOrDecorator, target),
) as TResult;
}
/**
* Retrieve metadata for a specified decorator for a specified set of targets and merge results.
*
* @param decorator lookup decorator for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAllAndMerge<T extends ReflectableDecorator<any>>(
decorator: T,
targets: (Type<any> | Function)[],
): T extends ReflectableDecorator<infer R> ? R : unknown;
/**
* Retrieve metadata for a specified key for a specified set of targets and merge results.
*
* @param metadataKey lookup key for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAllAndMerge<TResult extends any[] | object = any[], TKey = any>(
metadataKey: TKey,
targets: (Type<any> | Function)[],
): TResult;
/**
* Retrieve metadata for a specified key or decorator for a specified set of targets and merge results.
*
* @param metadataKeyOrDecorator lookup key for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAllAndMerge<TResult extends any[] | object = any[], TKey = any>(
metadataKeyOrDecorator: TKey,
targets: (Type<any> | Function)[],
): TResult {
const metadataCollection = this.getAll<any[], TKey>(
metadataKeyOrDecorator,
targets,
).filter(item => item !== undefined);
if (isEmpty(metadataCollection)) {
return metadataCollection as TResult;
}
return metadataCollection.reduce((a, b) => {
if (Array.isArray(a)) {
return a.concat(b);
}
if (isObject(a) && isObject(b)) {
return {
...a,
...b,
};
}
return [a, b];
});
}
/**
* Retrieve metadata for a specified decorator for a specified set of targets and return a first not undefined value.
*
* @param decorator lookup decorator for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAllAndOverride<T extends ReflectableDecorator<any>>(
decorator: T,
targets: (Type<any> | Function)[],
): T extends ReflectableDecorator<infer R> ? R : unknown;
/**
* Retrieve metadata for a specified key for a specified set of targets and return a first not undefined value.
*
* @param metadataKey lookup key for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAllAndOverride<TResult = any, TKey = any>(
metadataKey: TKey,
targets: (Type<any> | Function)[],
): TResult;
/**
* Retrieve metadata for a specified key or decorator for a specified set of targets and return a first not undefined value.
*
* @param metadataKeyOrDecorator lookup key or metadata for metadata to retrieve
* @param targets context (decorated objects) to retrieve metadata from
*
*/
public getAllAndOverride<TResult = any, TKey = any>(
metadataKeyOrDecorator: TKey,
targets: (Type<any> | Function)[],
): TResult {
for (const target of targets) {
const result = this.get(metadataKeyOrDecorator, target);
if (result !== undefined) {
return result;
}
}
return undefined;
}
}