Set additional property descriptor flags when updating request 'heade…

…rs' segment

Set the 'configurable', 'enumerable', and 'writable' flags when updating the 'headers' segment with the validated results. An update to header parsing in Node 15 (nodejs/node#35281) resulted in these no longer being set on the IncomingMessage.headers property which led to a 'Cannot assign to read only property' TypeError if the celebrate middleware tries to update the 'headers' segment multiple times per request.

lib/celebrate.js

@@ -25,6 +25,14 @@ const internals = {
   },
 };
 
+internals.segmentPropertyDescriptors = {
+  [segments.HEADERS]: {
+    configurable: true,
+    enumerable: true,
+    writable: true,
+  }
+};
+
 internals.validateSegment = (segment) => (spec, joiConfig) => {
   const finalValidate = (req) => spec.validateAsync(req[segment], joiConfig);
   finalValidate.segment = segment;
@@ -87,6 +95,7 @@ internals.partialValidate = (steps, req) => steps.reduce((chain, validate) => ch
     if (value != null) {
       Object.defineProperty(req, validate.segment, {
         value,
+        ...internals.segmentPropertyDescriptors[validate.segment],
       });
     }
     return null;
@@ -119,6 +128,7 @@ internals.fullValidate = (steps, req) => {
     requestUpdates.forEach((result) => {
       Object.defineProperty(req, result[0], {
         value: result[1],
+        ...internals.segmentPropertyDescriptors[result[0]],
       });
     });