[PoC] feat(rest): add type coercion for parseParams

packages/rest/package.json

@@ -32,7 +32,8 @@
     "http-errors": "^1.6.3",
     "js-yaml": "^3.11.0",
     "lodash": "^4.17.5",
-    "path-to-regexp": "^2.2.0"
+    "path-to-regexp": "^2.2.0",
+    "tiny-coerce": "^1.0.1"
   },
   "devDependencies": {
     "@loopback/build": "^0.6.0",

packages/rest/src/parser.ts

@@ -18,6 +18,8 @@ import {
   PathParameterValues,
 } from './internal-types';
 import {ResolvedRoute} from './router/routing-table';
+const coerce = require('tiny-coerce');
+const debug = require('debug')('loopback:rest:parser');
 type HttpError = HttpErrors.HttpError;
 
 // tslint:disable-next-line:no-any
@@ -124,5 +126,14 @@ function buildOperationArguments(
     }
   }
   if (requestBodyIndex > -1) paramArgs.splice(requestBodyIndex, 0, body);
-  return paramArgs;
+
+  debug('Coercing parameters', paramArgs);
+
+  const coercedParamArgs: OperationArgs = [];
+  for (const arg of paramArgs) {
+    debug('Coercing parameter', arg);
+    coercedParamArgs.push(typeof arg === 'object' ? arg : coerce(arg));
+  }
+
+  return coercedParamArgs;
 }

packages/rest/test/acceptance/coercion/coercion.acceptance.ts

@@ -0,0 +1,83 @@
+import {supertest, createClientForHandler, sinon} from '@loopback/testlab';
+import {
+  RestApplication,
+  RestServer,
+  get,
+  param,
+  post,
+  requestBody,
+} from '../../..';
+
+describe('Coercion', () => {
+  let app: RestApplication;
+  let server: RestServer;
+  let client: supertest.SuperTest<supertest.Test>;
+
+  before(givenAnApplication);
+  before(givenAServer);
+  before(givenAClient);
+
+  after(async () => {
+    await app.stop();
+  });
+
+  class MyController {
+    @get('/create-number/{num}')
+    getNumber(@param.path.number('num') num: number) {
+      return num;
+    }
+
+    @get('/create-boolean')
+    getBoolean(@param.query.boolean('bool') bool: boolean) {
+      return bool;
+    }
+
+    @post('/create-object/')
+    createObject(@requestBody() obj: object) {}
+  }
+
+  it('coerces a number', async () => {
+    const spy = sinon.spy(MyController.prototype, 'getNumber');
+    await client.get('/create-number/13').expect(200);
+    sinon.assert.calledWithExactly(spy, 13);
+    sinon.assert.neverCalledWith(spy, '13');
+    spy.restore();
+  });
+
+  it('coerces "false" into a boolean', async () => {
+    const spy = sinon.spy(MyController.prototype, 'getBoolean');
+    await client.get('/create-boolean?bool=false').expect(200);
+    sinon.assert.calledWithExactly(spy, false);
+    sinon.assert.neverCalledWith(spy, 'false');
+    spy.restore();
+  });
+
+  it('coerces "true" into a boolean', async () => {
+    const spy = sinon.spy(MyController.prototype, 'getBoolean');
+    await client.get('/create-boolean?bool=true').expect(200);
+    sinon.assert.calledWithExactly(spy, true);
+    sinon.assert.neverCalledWith(spy, 'true');
+    spy.restore();
+  });
+
+  it('works with requestBody', async () => {
+    await client
+      .post('/create-object')
+      .send({foo: 'bar'})
+      .expect(200);
+  });
+
+  async function givenAnApplication() {
+    app = new RestApplication();
+    app.controller(MyController);
+    await app.start();
+  }
+
+  async function givenAServer() {
+    server = await app.getServer(RestServer);
+  }
+
+  async function givenAClient() {
+    client = await createClientForHandler(server.requestHandler);
+  }
+});