add getMetadataFromDecorator

.npmignore

@@ -10,4 +10,5 @@ Dockerfile
 /dist/test
 /src
 /tests
-/dist/tests
+/dist/tests
\ No newline at end of file
+/build.js

src/def/decorator-types.ts

+export type AllDecorators = MethodDecorator &
+  ClassDecorator &
+  PropertyDecorator;
+
+export type AnyDecorators =
+  | MethodDecorator
+  | ClassDecorator
+  | PropertyDecorator
+  | ParameterDecorator;

src/def/index.ts

 export * from './interfaces';
+export * from './decorator-types';

src/reflector.ts

 import 'reflect-metadata';
-import { ArrayValue, GenericMap, Key, MapValue, StringDict } from './def';
+import {
+  AnyDecorators,
+  ArrayValue,
+  GenericMap,
+  Key,
+  MapValue,
+  StringDict,
+} from './def';
 import { getClass } from './utility/utility';
 
 export class Reflector<M extends StringDict, AM extends StringDict> {
@@ -41,4 +48,16 @@ export class Reflector<M extends StringDict, AM extends StringDict> {
       ...valueFromProperty,
     ] as ArrayValue<AM, K>;
   }
+
+  getMetadataFromDecorator<K extends Key<GenericMap<M, AM>>>(
+    dec: AnyDecorators,
+    metadataKey: K,
+  ): MapValue<M, AM, K> {
+    const _dec = dec as PropertyDecorator;
+    class TempClass {}
+    const propertyKey =
+      '_temp_property_key_' + Math.random().toString(16).slice(2);
+    _dec(TempClass.prototype, propertyKey);
+    return this.get(metadataKey, TempClass, propertyKey);
+  }
 }

src/setter.ts

 import 'reflect-metadata';
-import { ArrayValueMap, GenericMap, Key, MergeKey, StringDict } from './def';
+import { AllDecorators, ArrayValueMap, GenericMap, Key, MergeKey, StringDict } from './def';
 import { getClass } from './utility/utility';
 
-export type AllDecorators = MethodDecorator &
-  ClassDecorator &
-  PropertyDecorator;
-
 export class MetadataSetter<M extends StringDict, AM extends StringDict> {
   private getMetadataInDecorator<
     K extends MergeKey<M, AM>,

tests/reflect.spec.ts

@@ -212,4 +212,29 @@ describe('Reflector', () => {
     expect(reflector.get('bar', A, 'staticMethod')).toStrictEqual([5, 6]);
     expect(reflector.get('bar', a, 'staticMethod')).toStrictEqual([5, 6]);
   });
+
+  it('should get metadata from decorator', () => {
+    const classDec: ClassDecorator = Metadata.set('foo', 'class-decorator');
+    const propDec: PropertyDecorator = Metadata.set(
+      'foo',
+      'property-decorator',
+    );
+    const methodDec: MethodDecorator = Metadata.set('foo', 'method-decorator');
+
+    const transDec = Metadata.append('bar', 444);
+
+    expect(reflector.getMetadataFromDecorator(classDec, 'foo')).toEqual(
+      'class-decorator',
+    );
+
+    expect(reflector.getMetadataFromDecorator(propDec, 'foo')).toEqual(
+      'property-decorator',
+    );
+
+    expect(reflector.getMetadataFromDecorator(methodDec, 'foo')).toEqual(
+      'method-decorator',
+    );
+
+    expect(reflector.getMetadataFromDecorator(transDec, 'bar')).toEqual([444]);
+  });
 });