check if writable end in both fileResponse as well as response end

Author: ujjwalguptaofficial

src/handlers/file_handler.ts

@@ -119,7 +119,7 @@ export class FileHandler {
         });
     }
 
-    protected sendFileAsResponse(filePath: string, mimeType: MIME_TYPE) {
+    private sendFileAsResponse_(filePath: string, mimeType: MIME_TYPE) {
         return promise((res, rej) => {
             const handler = this.option;
             const readStream = Fs.createReadStream(filePath);
@@ -136,12 +136,16 @@ export class FileHandler {
     }
 
     send(filePathInfo: IFileResultInfo) {
+        const response = this.option.response;
+        if (response.writableEnded || response.headersSent) {
+            console.warn("FileHandler.send called after response was already sent/ended");
+            return;
+        }
         const { fileInfo, filePath } = filePathInfo;
         const lastModified = fileInfo.mtime.toUTCString();
         const eTagValue = etag(fileInfo, {
             weak: this.option.global.eTag.type === ETAG_TYPE.Weak
         });
-        const response = this.option.response;
         response.setHeader('Etag', eTagValue);
         const extension = path.parse(filePath).ext;
         const contentType = response.getHeader(CONTENT_TYPE);
@@ -154,7 +158,7 @@ export class FileHandler {
         }
         else {
             response.setHeader('Last-Modified', lastModified);
-            return this.sendFileAsResponse(filePath, mimeType);
+            return this.sendFileAsResponse_(filePath, mimeType);
         }
     }
 

src/handlers/request_handler_helper.ts

@@ -77,6 +77,10 @@ export class RequestHandlerHelper {
     // which was not supposed to be done
     // then you don't follow regular rules but just throw them from anywhere
     onErrorOccured(error) {
+        if (this.response.headersSent) {
+            console.log("Response already sent, cannot send error response");
+            return;
+        }
         if (typeof error === 'string') {
             error = {
                 message: error
@@ -162,14 +166,18 @@ export class RequestHandlerHelper {
             }
         ) : "";
 
-        if (this.response.headersSent) {
+        const response = this.response;
+
+        // double check to avoid multiple end calls
+        // placement is before writing head to avoid writing head multiple times
+        if (response.headersSent || response.writableEnded) {
             console.trace("Request is finished, but triggered again");
             return;
         }
 
-        this.response.writeHead(this.controllerResult.statusCode || HTTP_STATUS_CODE.Ok,
+        response.writeHead(this.controllerResult.statusCode || HTTP_STATUS_CODE.Ok,
             { [CONTENT_TYPE]: negotiateMimeType });
-        this.response.end(data);
+        response.end(data);
     }
 
     private async handleCustomResult_() {