Adding joi validation for other content than the request body like qu…

…ery parameter or something else in the request or context (#4)

README.md

@@ -62,13 +62,23 @@ The body of the response could be customized by adding a transformer like in the
 
 ```typescript
 export default middleware(handler, [
-  validation(accountWithConnectionRequestSchema(), (message) => ({
+  validation(schema, (message) => ({
     type: 'Invalid  request object',
     detail: message,
   })),
 ])
 ```
 
+By default the request body is getting validated. To validate other parts of the request or context the `extractValidationContentFromRequest` function could be used, when initializing the middleware.
+
+```typescript
+export default middleware(handler, [
+  validation(schema, undefined, (req, context) => req.query.name)),
+])
+```
+
+In this example the `name` contained in the query is getting validated against the passed request.
+
 ### Authorization
 
 To authorize a request the middleware function `authorization` could be used. The function is verifying a request parameter against a JWT Bearer Token. The information get extracted using two functions for the correct parameter and token counterpart.

src/validation.test.ts

@@ -27,13 +27,14 @@ describe('The joi validator should', () => {
         expect(result).toBeUndefined();
     });
 
-    test('not call the validation when the method is GET', async () => {
+    test('successfully validate the object extracted through the passed function', async () => {
         requestMock.method = 'GET';
         const schemaMock = mock<JoiValidator.ObjectSchema>();
+        schemaMock.validate.mockReturnValue({ error: undefined, value: 'Test Validation' });
 
-        const result = await sut(schemaMock)(contextMock, requestMock);
+        const result = await sut(schemaMock, undefined, () => 'test-extracted-content')(contextMock, requestMock);
 
-        expect(schemaMock.validate).not.toBeCalled();
+        expect(schemaMock.validate).toBeCalledWith('test-extracted-content');
         expect(result).toBeUndefined();
     });
 

src/validation.ts

@@ -3,25 +3,29 @@ import { ObjectSchema } from 'joi';
 import { ApplicationError } from './applicationError';
 import { MiddlewareFunction } from './middleware';
 
-export default (schema: ObjectSchema, transformErrorMessage?: (message: string) => unknown): MiddlewareFunction => {
+export default (
+    schema: ObjectSchema,
+    transformErrorMessage?: (message: string) => unknown,
+    extractValidationContentFromRequest?: (context: Context, req: HttpRequest) => unknown,
+): MiddlewareFunction => {
     return (context: Context, req: HttpRequest): Promise<void> => {
-        const body = req.body;
-        if (req.method !== 'GET') {
-            const validationResult = schema.validate(body);
-            if (validationResult && validationResult.error) {
-                context.log.verbose(validationResult);
-                return Promise.reject(
-                    new ApplicationError(
-                        'Validation Error',
-                        400,
-                        transformErrorMessage
-                            ? transformErrorMessage(validationResult.error.message)
-                            : {
-                                  message: validationResult.error.message,
-                              },
-                    ),
-                );
-            }
+        const toBeValidatedContent = extractValidationContentFromRequest
+            ? extractValidationContentFromRequest(context, req)
+            : req.body;
+        const validationResult = schema.validate(toBeValidatedContent);
+        if (validationResult && validationResult.error) {
+            context.log.verbose(validationResult);
+            return Promise.reject(
+                new ApplicationError(
+                    'Validation Error',
+                    400,
+                    transformErrorMessage
+                        ? transformErrorMessage(validationResult.error.message)
+                        : {
+                              message: validationResult.error.message,
+                          },
+                ),
+            );
         }
         return Promise.resolve();
     };