Cypress’ parallel mode overwrites files among Cypress instances

[romankhomitskyi]

Current behavior

My Cypress test specs are coded in TypeScript. Compiling TypeScript code in Cypress’ parallel mode causes overwriting in files among Cypress instances

I am getting the following errors on CI

• Invalid or unexpected token
• Unexpected end of input
• Failed to execute 'atob' on 'Window'
• is not a function, however it is a function and works OK on local and without parallel mode, or with work around

And also this error in this issue #9442

The only workaround is to isolate test files in their test runs, so test code will not get overwritten by other instances

I have this code to append unique IDs to filenames before Webpack processes test files in cypress.config.ts

import { v4 as uuid } from "uuid";

import webpackPreprocessor from "@cypress/webpack-batteries-included-preprocessor";

const filePreprocessor = webpackPreprocessor({ typescript: "typescript" });

const id = uuid();
on("file:preprocessor", (file) => {
  file.outputPath = file.outputPath.replace(
    /^(.*\/)(.*?)(\..*)$/,
    `$1$2.${id}$3`
  );
  console.log("File output", file.outputPath);
  return filePreprocessor(file);
});

The path will be replaced with “specs/my_feature/abc.<uuid>.spec.ts”. is unique among each cypress instances.

Desired behavior

Cypress should not overwrite files among Cypress instances
It should be implemented under the hood

Test code to reproduce

I run 58 cypress instances in one container which is starting in one Gitlab job

Overall I have the following flow

4 parallel gitlab jobs
4 cypress docker container in each
58 cypress instances in each container

I am using AWS spot instances

Cypress Version

12.5.0

Node version

18.13.0

Operating System

Debian, cypress/factory docker image

Debug Logs

No response

Other

No response

[AtofStryker]

Hi @romankhomitskyi . Thank you for opening an issue. This seems like it might be a hard issue to reproduce. Is there anyway we can get a small scale reproduction repository going that shows the issues with the file overwriting with the preprocessor? Also what version of Typescript are you using?

[romankhomitskyi]

Hi @romankhomitskyi . Thank you for opening an issue. This seems like it might be a hard issue to reproduce. Is there anyway we can get a small scale reproduction repository going that shows the issues with the file overwriting with the preprocessor? Also what version of Typescript are you using?

Typescript: 4.9.5, and oldest

Here is an article describing a problem and solution to this issue

https://link.medium.com/Q9YrwZGaryb

Also @BlueWinds confirmed that is a root cause

#9442

[romankhomitskyi]

The reproduction is a running multiple cypress runner instances on the same machine, which is not recommended but anyway, they should not mutate each other

[emilyrohrbough]

@romankhomitskyi Yeah, Cypress is not setup out-of-the box to run in parallel on the same machine. The webpack output is assuming a single directory when leveraging the cypress/webpack-preprocessor and the way we load these processed files in, we assume the are already unique. The solution you posted is the correct path forward. I will flag as an enhacement for our team to consider.