fix: force gzip when no accept encoding header is sent and use identity if gzip is not sent

[ryanthemanuel]

• Closes Ensure that deflate/brotli is filtered out in Accept Encoding by the Cypress proxy #28025

Additional details

Currently, Cypress tries to filter down Accept-Encoding headers to just gzip. This works when the header is present, but when it is blank according to the standards for the header:

If no Accept-Encoding header field is in the request, any content coding is considered acceptable by the user agent.

Thus, we need to update the logic to specify identity when there is no Accept Encoding header.

The problem would manifest itself in the following scenario:

1. No Accept-Encoding header is sent on a request
2. The server sends back the response encoded in an unsupported encoding (e.g. brotli/deflate)
3. Something in Cypress relies on the decompressed body (this could include cy.intercept or CSS, font, and image assets in Test Replay)

Steps to test

1. Set up a server that returns brotli encoded assets when no Accept Encoding header is specified.
2. Record a Cypress run where assets don't request an Accept Encoding.
3. Ensure that Test Replay is still functional

How has the user experience changed?

n/a

PR Tasks

• Have tests been added/updated?
• [na] Has a PR for user-facing changes been opened in cypress-documentation?
• [na] Have API changes been updated in the type definitions?

[cypress]

34 flaky tests on run #51660 ↗︎

0

28144

1345

0

34

Details:

Merge branch 'develop' into ryanm/fix/issue-with-brotli-and-deflate
Project: cypress	Commit: 04a6eed88d
Status: Passed	Duration: 18:40 💡
Started: Oct 16, 2023 8:00 PM	Ended: Oct 16, 2023 8:19 PM

  commands/net_stubbing.cy.ts • 2 flaky tests • 5x-driver-firefox

View Output Video

Test		Artifacts
network stubbing > intercepting request > can delay with deprecated delayMs param		Output
network stubbing > intercepting request > delay works correctly with 204 No Content		Output

  e2e/origin/commands/assertions.cy.ts • 1 flaky test • 5x-driver-firefox

View Output Video

Test		Artifacts
cy.origin assertions > #consoleProps > .should() and .and()		Output

  cypress/cypress.cy.js • 3 flaky tests • 5x-driver-firefox

View Output Video

Test		Artifacts
... > correctly returns currentRetry		Output
... > correctly returns currentRetry		Output
... > correctly returns currentRetry		Output

  runs.cy.ts • 1 flaky test • app-e2e

View Output Video

Test		Artifacts
... > opens the run page if a run is clicked		Test Replay Output Screenshots

  scaffold-component-testing.cy.ts • 1 flaky test • launchpad-e2e

View Output Video

Test		Artifacts
scaffolding component testing > create-react-app > scaffolds component testing for Create React App v5 project		Test Replay Output Screenshots

The first 5 flaky specs are shown, see all 20 specs in Cypress Cloud.

Review all test suite changes for PR #28026 ↗︎

[cypress-bot]

Released in 13.3.2.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
Cypress v13.3.2, please open a new issue.