fix: Remove error message wrapping of Cypress.Blob return values

[chrisbreiding]

• Closes Remove .then wrap from return value of Cypress.Blob.base64StringToBlob #8365

User facing changelog

• Cypress no longer adds a .then method to the return value of Cypress.Blob methods for the sake of a custom error message. Fixes an issue where those return values were mistaken for promises and unintentionally trigger the custom error.

Additional details

There is no longer a custom error message for using the old promise-returning API of Blob methods, but it makes it easier to wrap those methods for backwards compatibility. I think this an okay compromise.

How has the user experience changed?

Before, this would incorrectly error:

Cypress.Promise.resolve(Cypress.Blob.base64StringToBlob(btoa('foo'))
// => throws error 'base64StringToBlob() no longer returns a Promise. Update the use of base64StringToBlob() to expect a returned Blob'

Now it does not error:

Cypress.Promise.resolve(Cypress.Blob.base64StringToBlob(btoa('foo'))
// => returns promise with base64 value

The error experience of using .then has degraded a bit:

Before:

Cypress.Blob.base64StringToBlob(btoa('foo').then(() => {})
// => throws error 'base64StringToBlob() no longer returns a Promise. Update the use of base64StringToBlob() to expect a returned Blob'

After:

Cypress.Blob.base64StringToBlob(btoa('foo').then(() => {})
// => throws error '.then is not a function'

PR Tasks

• Have tests been added/updated?
• Has the original issue been tagged with a release in ZenHub?

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[cypress]

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Test summary

8134 • 0 • 108 • 3

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Run details

Project	cypress
Status	Passed
Commit	fbaf084
Started	Aug 20, 2020 4:31 PM
Ended	Aug 20, 2020 4:38 PM
Duration	06:56 💡
OS	Linux Debian - 10.2
Browser	Multiple

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