fix: handle case of implicit plugins/index.js files during migration

[lmiller1990]

• Closes Migration Helper loads endlessly #22461

User facing changelog

Fix a bug in migration where the old pluginsFile API is not respected during migration, causing the migration tool to hang without a response.

Additional details

The migration tool is not respecting when pluginsFile points to a directory containing index.js. For example:

- root
--- cypress
------ plugins
-------- index.js

If you set your cypress.json to

{
   "pluginsFile": "cypress/plugins"
}

Cypress 9 would figure out you wanted cypress/plugins/index.js, since we just did require(config.pluginsFile). It's not really documented, but it worked, so we should respect this during migration.

Although this was not explicitly documented, users coming from this usage encounter a migration screen that doesn't show any error, which is a terrible first experience when using Cypress 10, so I think it's better to just support this than error confusingly.

Steps to test

1. Grab reproduction from Migration Helper loads endlessly #22461
2. Try to migrate it

Note: supportFile pointing to a directory with index.js also worked previously, although not explicitly documented. This throws a reasonable error telling the user the problem, so it's not as problematic as the case of pluginsFile, where it just sat on a screen with a spinner.

How has the user experience changed?

Can migrate without getting stuck.

PR Tasks

• Have tests been added/updated?
• Has the original issue (or this PR, if no issue exists) been tagged with a release in ZenHub? (user-facing changes only)
• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?

[cypress-bot]

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[cypress]

---

Test summary

37681 • 0 • 456 • 0 • 13

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Run details

Project	cypress
Status	Passed
Commit	41c3f44
Started	Jun 24, 2022 7:38 AM
Ended	Jun 24, 2022 7:55 AM
Duration	16:54 💡
OS	Linux Debian - 10.11
Browser	Multiple

View run in Cypress Dashboard ➡️

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Flakiness

	actions/click.cy.js		1
1	... > scroll-behavior > can scroll to and click elements in html with scroll-behavior: smooth
	xhr.cy.js		4
1	... > logs request + response headers
2	... > logs Method, Status, URL, and XHR
3	... > logs response
4	... > logs Method, Status, URL, and XHR
This comment includes only the first 5 flaky tests. See all 13 flaky tests in the Cypress Dashboard.

---

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[emilyrohrbough]

Suggested change

	throw Error(`Could not find pluginsFile. Received projectRoot ${projectRoot} and pluginPath: ${pluginPath}`)
	throw Error(`Could not find pluginsFile in %s`, pluginLoc)

[tbiethman]

Works good. I appreciate the extra logs in here 👍

[cypress-bot]

Released in 10.3.0.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
Cypress v10.3.0, please open a new issue.