Add decorator feature and tests (#71)

* Add decorator feature and tests

* Avoid warning

* Remove unwanted change

package.json

@@ -43,5 +43,7 @@
     },
     "testEnvironment": "node"
   },
-  "dependencies": {}
+  "dependencies": {
+    "reflect-metadata": "^0.1.12"
+  }
 }

src/decorator.spec.ts

@@ -0,0 +1,125 @@
+import { check, checked, String } from '.';
+
+describe('Decorators', () => {
+  describe('@checked', () => {
+    describe('parameter length', () => {
+      it('works', () => {
+        expect(() => {
+          class Class {
+            @checked(String)
+            static method(s: string) {
+              return s;
+            }
+          }
+          return Class;
+        }).not.toThrow();
+        expect(() => {
+          class Class {
+            @checked(String, String)
+            static method(s: string) {
+              return s;
+            }
+          }
+          return Class;
+        }).toThrow();
+        expect(() => {
+          class Class {
+            @checked()
+            static method(s: string) {
+              return s;
+            }
+          }
+          return Class;
+        }).toThrow();
+        expect(() => {
+          class Class {
+            @checked(String, String)
+            static method(s: string = 'initial', t: string = 'initial') {
+              return { s, t };
+            }
+          }
+          return Class;
+        }).not.toThrow();
+      });
+    });
+    describe('parameter check', () => {
+      it('works', () => {
+        class Class {
+          @checked(String)
+          static method1(s: string) {
+            return s;
+          }
+          @checked(String.withConstraint(s => /^world$/.test(s)))
+          static method2(s: string) {
+            return s;
+          }
+        }
+        expect(() => {
+          Class.method1('hello');
+        }).not.toThrow();
+        expect(() => {
+          Class.method2('hello');
+        }).toThrow(/Failed constraint check/);
+        expect(() => {
+          Class.method2('world');
+        }).not.toThrow();
+      });
+    });
+  });
+  describe('@check', () => {
+    describe('parameter length', () => {
+      it('works', () => {
+        expect(() => {
+          class Class {
+            @checked(String)
+            static method(@check s: string) {
+              return s;
+            }
+          }
+          return Class;
+        }).not.toThrow();
+        expect(() => {
+          class Class {
+            @checked(String, String)
+            static method(@check s: string, t: string) {
+              return { s, t };
+            }
+          }
+          return Class;
+        }).toThrow();
+        expect(() => {
+          class Class {
+            @checked(String)
+            static method(@check s: string, t: string) {
+              return { s, t };
+            }
+          }
+          return Class;
+        }).not.toThrow();
+      });
+    });
+    describe('parameter check', () => {
+      it('works', () => {
+        class Class {
+          @checked(String)
+          static method1(@check s: string) {
+            return s;
+          }
+          @checked(String.withConstraint(s => /^world$/.test(s)))
+          static method2(s: string, @check t: string) {
+            return { s, t };
+          }
+        }
+        expect(() => {
+          Class.method1('hello');
+        }).not.toThrow();
+        expect(() => {
+          Class.method2('world', 'hello');
+        }).toThrow(/Failed constraint check/);
+        expect(() => {
+          Class.method2('hello', 'world');
+        }).not.toThrow();
+      });
+    });
+  });
+});

src/decorator.ts

@@ -0,0 +1,98 @@
+import { Runtype, ValidationError } from './runtype';
+
+import 'reflect-metadata';
+
+const CHECKED_PARAMETER_INDICES = Symbol.for('runtypes:checked-parameter-indices');
+
+/**
+ * A parameter decorator. Explicitly mark the parameter as checked on every method call in combination with `@checked` method decorator. The number of `@check` params must be the same as the number of provided runtypes into `@checked`.\
+ * Usage:
+ * ```ts
+ * @checked(Runtype1, Runtype3)
+ * method(@check p1: Runtype1, p2: number, @check p3: Runtype3) { ... }
+ * ```
+ */
+export function check(target: any, propertyKey: string | symbol, parameterIndex: number) {
+  const existingValidParameterIndices: number[] =
+    Reflect.getOwnMetadata(CHECKED_PARAMETER_INDICES, target, propertyKey) || [];
+  existingValidParameterIndices.push(parameterIndex);
+  Reflect.defineMetadata(
+    CHECKED_PARAMETER_INDICES,
+    existingValidParameterIndices,
+    target,
+    propertyKey,
+  );
+}
+
+/**
+ * A method decorator. Takes runtypes as arguments which correspond to the ones of the actual method.
+ *
+ * Usually, the number of provided runtypes must be _**the same as**_ or _**less than**_ the actual parameters.
+ *
+ * If you explicitly mark which parameter shall be checked using `@check` parameter decorator, the number of `@check` parameters must be _**the same as**_ the runtypes provided into `@checked`.
+ *
+ * Usage:
+ * ```ts
+ * @checked(Runtype1, Runtype2)
+ * method1(param1: Static1, param2: Static2, param3: any) {
+ *   ...
+ * }
+ *
+ * @checked(Runtype1, Runtype3)
+ * method2(@check param1: Static1, param2: any, @check param3: Static3) {
+ *   ...
+ * }
+ * ```
+ */
+export function checked(...runtypes: Runtype[]) {
+  if (runtypes.length === 0) {
+    throw new Error('No runtype provided to `@checked`. Please remove the decorator.');
+  }
+  return (target: any, propertyKey: string | symbol, descriptor: PropertyDescriptor) => {
+    const method: Function = descriptor.value!;
+    const className = target.name || target.constructor.name;
+    const methodId =
+      className +
+      (target.name ? '' : '.prototype') +
+      (typeof propertyKey === 'string' ? `["${propertyKey}"]` : `[${String(propertyKey)}]`);
+    const validParameterIndices: number[] | undefined = Reflect.getOwnMetadata(
+      CHECKED_PARAMETER_INDICES,
+      target,
+      propertyKey,
+    );
+    if (validParameterIndices) {
+      // if used with `@check` parameter decorator
+      if (runtypes.length === validParameterIndices.length) {
+        descriptor.value = function(...args: any[]) {
+          runtypes.forEach((type, typeIndex) => {
+            const parameterIndex = validParameterIndices[typeIndex];
+            try {
+              type.check(args[parameterIndex]);
+            } catch (err) {
+              throw new ValidationError(`${methodId}, argument #${parameterIndex}: ${err.message}`);
+            }
+          });
+
+          return method.apply(this, args);
+        };
+      } else {
+        throw new Error('Number of `@checked` runtypes and @valid parameters not matched.');
+      }
+    } else {
+      // if used without `@check` parameter decorator
+      if (runtypes.length <= method.length) {
+        descriptor.value = function(...args: any[]) {
+          runtypes.forEach((type, typeIndex) => {
+            try {
+              type.check(args[typeIndex]);
+            } catch (err) {
+              throw new ValidationError(`${methodId}, argument #${typeIndex}: ${err.message}`);
+            }
+          });
+        };
+      } else {
+        throw new Error('Number of `@checked` runtypes exceeds actual parameter length.');
+      }
+    }
+  };
+}

src/index.ts

@@ -23,3 +23,4 @@ export { InstanceOf } from './types/instanceof';
 export * from './types/lazy';
 export * from './types/constraint';
 export { Brand } from './types/brand';
+export * from './decorator';

tsconfig.json

@@ -9,7 +9,8 @@
     "declaration": true,
     "sourceMap": false,
     "outDir": "lib",
-    "forceConsistentCasingInFileNames": true
+    "forceConsistentCasingInFileNames": true,
+    "experimentalDecorators": true
   },
   "exclude": ["./lib/**/*", "./examples/**/*"]
 }

yarn.lock

@@ -2630,6 +2630,11 @@ realpath-native@^1.0.0:
   dependencies:
     util.promisify "^1.0.0"
 
+reflect-metadata@^0.1.12:
+  version "0.1.12"
+  resolved "https://registry.yarnpkg.com/reflect-metadata/-/reflect-metadata-0.1.12.tgz#311bf0c6b63cd782f228a81abe146a2bfa9c56f2"
+  integrity sha512-n+IyV+nGz3+0q3/Yf1ra12KpCyi001bi4XFxSjbiWWjfqb52iTTtpGXmCCAOWWIAn9KEuFZKGqBERHmrtScZ3A==
+
 regenerator-runtime@^0.11.0:
   version "0.11.1"
   resolved "https://registry.yarnpkg.com/regenerator-runtime/-/regenerator-runtime-0.11.1.tgz#be05ad7f9bf7d22e056f9726cee5017fbf19e2e9"