feat: keep original headers after validation

src/server/validation/validateRequest.test.ts

@@ -97,9 +97,9 @@ describe('validateRequest.headers', () => {
     })
 
     expect(response).toMatchObject({ ok: 1 })
-    expect(response.headers).toEqual({
+    expect(response.headers).toMatchObject({
       shortstring: 'shortstring',
-      numeric: 123,
+      numeric: '123',
       bool: '1',
       sessionid: 'sessionid',
     })
@@ -154,4 +154,56 @@ describe('validateRequest.headers', () => {
     expect(err.cause.message).toContain('"REDACTED": "REDACTED"')
     expect(err.cause.message).not.toContain('sessionid')
   })
+
+  test('should not replace the headers with the validated value by default', async () => {
+    const response = await app.get<TestResponse>('', {
+      headers: {
+        shortstring: 'shortstring',
+        numeric: '123',
+        bool: '1',
+        sessionid: 'sessionid',
+        foo: 'bar',
+      },
+    })
+
+    expect(response.headers).toMatchObject({
+      shortstring: 'shortstring',
+      numeric: '123',
+      bool: '1',
+      sessionid: 'sessionid',
+      foo: 'bar',
+    })
+  })
+
+  test('should replace the headers with the validated value when configured so', async () => {
+    const resource = getDefaultRouter().get('/', async (req, res) => {
+      validateRequest.headers(
+        req,
+        objectSchema<any>({
+          shortstring: stringSchema.min(8).max(16),
+          numeric: numberSchema,
+        }),
+        { keepOriginal: false },
+      )
+
+      res.json({ ok: 1, headers: req.headers })
+    })
+    const app = expressTestService.createAppFromResource(resource)
+
+    const response = await app.get<TestResponse>('', {
+      headers: {
+        shortstring: 'shortstring',
+        numeric: 123,
+        foo: 'bar',
+      },
+    })
+
+    expect(response.headers).toEqual({
+      shortstring: 'shortstring',
+      numeric: 123, // converted to number
+      // foo: 'bar' // fields not in the schema are removed
+    })
+
+    await app.close()
+  })
 })

src/server/validation/validateRequest.ts

@@ -16,6 +16,11 @@ export interface ReqValidationOptions<ERR extends Error> {
    * If true - `genericErrorHandler` will report it to errorReporter (aka Sentry).
    */
   report?: boolean | ((err: ERR) => boolean)
+
+  /**
+   * When set to true, the validated object will not be replaced with the Joi-converted value.
+   */
+  keepOriginal?: boolean
 }
 
 /**
@@ -55,12 +60,25 @@ class ValidateRequest {
     return this.validate(req, 'params', schema, opt)
   }
 
+  /**
+   * Validates `req.headers` against the provided Joi schema.
+   *
+   * Note: as opposed to other methods, this method does not mutate `req.headers` in case of success,
+   * i.e. schemas that cast values will not have any effect.
+   *
+   * If you wish to mutate `req.headers` with the validated value, use `keepOriginal: false` option.
+   * Keep in mind that this will also remove all values that are not in the schema.
+   */
   headers<T>(
     req: BackendRequest,
     schema: AnySchema<T>,
     opt: ReqValidationOptions<JoiValidationError> = {},
   ): T {
-    return this.validate(req, 'headers', schema, opt)
+    const options: ReqValidationOptions<JoiValidationError> = {
+      keepOriginal: true,
+      ...opt,
+    }
+    return this.validate(req, 'headers', schema, options)
   }
 
   private validate<T>(
@@ -92,7 +110,10 @@ class ValidateRequest {
     }
 
     // mutate req to replace the property with the value, converted by Joi
-    req[reqProperty] = value
+    if (!opt.keepOriginal) {
+      req[reqProperty] = value
+    }
+
     return value
   }
 }