feat(rest): improve validation errors for invalid parameter value

Rework the validation code to use exiting `RestHttpErrors.invalidData`
error instead of a custom `BadRequest` error. This way the error object
includes the parameter name in the error message & properties and has
a machine-readable `code` property.

Signed-off-by: Miroslav Bajtoš <[email protected]>

packages/rest/src/__tests__/acceptance/coercion/coercion.acceptance.ts

@@ -15,6 +15,7 @@ import {
 import {
   Client,
   createRestAppClient,
+  expect,
   givenHttpServerConfig,
   sinon,
 } from '@loopback/testlab';
@@ -253,6 +254,34 @@ describe('Coercion', () => {
     sinon.assert.calledWithExactly(spy, {...inclusionFilter});
   });
 
+  it('returns AJV validation errors in error details', async () => {
+    const filter = {
+      where: 'string-instead-of-object',
+    };
+    const response = await client
+      .get(`/nested-inclusion-from-query`)
+      .query({filter: JSON.stringify(filter)})
+      .expect(400);
+
+    expect(response.body.error).to.containDeep({
+      code: 'INVALID_PARAMETER_VALUE',
+      details: [
+        {
+          code: 'type',
+          info: {
+            type: 'object',
+          },
+          message: 'should be object',
+          path: '/where',
+        },
+      ],
+    });
+
+    expect(response.body.error.message).to.match(
+      /Invalid data.* for parameter "filter"/,
+    );
+  });
+
   async function givenAClient() {
     app = new RestApplication({rest: givenHttpServerConfig()});
     app.controller(MyController);

packages/rest/src/coercion/coerce-parameter.ts

@@ -187,7 +187,7 @@ async function coerceObject(
       data,
       schema,
       {},
-      {...options, coerceTypes: true, source: 'parameter'},
+      {...options, coerceTypes: true, source: 'parameter', name: spec.name},
     );
   }
 

packages/rest/src/rest-http-error.ts

@@ -11,7 +11,7 @@ export namespace RestHttpErrors {
     name: string,
     extraProperties?: Props,
   ): HttpErrors.HttpError & Props {
-    const msg = `Invalid data ${JSON.stringify(data)} for parameter ${name}!`;
+    const msg = `Invalid data ${JSON.stringify(data)} for parameter "${name}".`;
     return Object.assign(
       new HttpErrors.BadRequest(msg),
       {
@@ -51,11 +51,15 @@ export namespace RestHttpErrors {
 
   export const INVALID_REQUEST_BODY_MESSAGE =
     'The request body is invalid. See error object `details` property for more info.';
-  export function invalidRequestBody(): HttpErrors.HttpError {
+
+  export function invalidRequestBody(
+    details: ValidationErrorDetails[],
+  ): HttpErrors.HttpError & {details: ValidationErrorDetails[]} {
     return Object.assign(
       new HttpErrors.UnprocessableEntity(INVALID_REQUEST_BODY_MESSAGE),
       {
         code: 'VALIDATION_FAILED',
+        details,
       },
     );
   }

packages/rest/src/types.ts

@@ -117,6 +117,11 @@ export interface ValueValidationOptions extends ValidationOptions {
    * 'query', 'cookie', etc...
    */
   source?: string;
+
+  /**
+   * Parameter name, as provided in `ParameterObject#name` property.
+   */
+  name?: string;
 }
 
 /**

packages/rest/src/validation/request-body.validator.ts

@@ -12,7 +12,6 @@ import {
 } from '@loopback/openapi-v3';
 import ajv, {Ajv} from 'ajv';
 import debugModule from 'debug';
-import _ from 'lodash';
 import util from 'util';
 import {HttpErrors, RequestBody, RestHttpErrors} from '..';
 import {
@@ -180,30 +179,32 @@ export async function validateValueAgainstSchema(
 
   // Throw invalid request body error
   if (options.source === 'body') {
-    const error = RestHttpErrors.invalidRequestBody();
-    addErrorDetails(error, validationErrors);
+    const error = RestHttpErrors.invalidRequestBody(
+      buildErrorDetails(validationErrors),
+    );
     throw error;
   }
 
   // Throw invalid value error
-  const error = new HttpErrors.BadRequest('Invalid value.');
-  addErrorDetails(error, validationErrors);
+  const error = RestHttpErrors.invalidData(value, options.name ?? '(unknown)', {
+    details: buildErrorDetails(validationErrors),
+  });
   throw error;
 }
 
-function addErrorDetails(
-  // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  error: any,
+function buildErrorDetails(
   validationErrors: ajv.ErrorObject[],
-) {
-  error.details = _.map(validationErrors, e => {
-    return {
-      path: e.dataPath,
-      code: e.keyword,
-      message: e.message,
-      info: e.params,
-    };
-  });
+): RestHttpErrors.ValidationErrorDetails[] {
+  return validationErrors.map(
+    (e: ajv.ErrorObject): RestHttpErrors.ValidationErrorDetails => {
+      return {
+        path: e.dataPath,
+        code: e.keyword,
+        message: e.message ?? `must pass validation rule ${e.keyword}`,
+        info: e.params,
+      };
+    },
+  );
 }
 
 /**