fix(NODE-5925): driver throws error when non-read operation in a transaction has a ReadPreferenceMode other than 'primary'

[aditi-khare-mongoDB]

Description

Within a transaction, readPreferences != 'primary' are not supported, and our error logic must support that to comply with spec. An error should only be thrown in these circumstances when a read operation is being executed.

What is changing?

In a transaction, when a user provides a readPreference != 'primary' and then tries to perform a command that involves a read, the Node Driver will now throw a

Is there new documentation needed for these changes?

Yes, update Transactions Node.js Manual to reflect desired readPreference inputs.

What is the motivation for this change?

See Release Highlights

Release Highlight

Don't throw error when non-read operation in a transaction has a ReadPreferenceMode other than 'primary'

The following error will now only be thrown when a user provides a ReadPreferenceMode other than primary and then tries to perform a command that involves a read:

new MongoTransactionError('Read preference in a transaction must be primary');

Prior to this change, the Node Driver would incorrectly throw this error even when the operation does not perform a read.
Note: a RunCommandOperation is treated as a read operation for this error.

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[nbbeeken]

Suggested change

	(operation.hasAspect(Aspect.READ_OPERATION) || operation.commandName === 'runCommand')
	(operation.hasAspect(Aspect.READ_OPERATION) || operation.commandName === 'runCommand')

Very minor but a handful of lines down we check for read/write aspect, can we move those variable declarations up here and reuse the result of this call? I figure we can just reuse the same work once.

[aditi-khare-mongoDB]

Yep, I've moved the isReadOperation up in the function!