Improve S3776: Exclude complexity of JSX attribute short-circuits

[gabriel-vivas-sonarsource]

Label	Description
Rule	S3776 "Cognitive Complexity of functions should not be too high"
FP Example	* Short-circuits in JSX attribute values

Explanation

In JSX, it is fairly common to use short-circuit logic for conditionally rendering values. Currently, we count this as Cognitive Complexity.

See example:

• https://sonarcloud.io/project/issues?resolved=false&rules=javascript%3AS3776&id=gabriel-vivas-sonarsource_caronte-tool&open=AYIcpFGSkChixz00fwGY

See the dogwood thread (internal):

• https://discuss.sonarsource.com/t/cognitive-complexity-and-jsx-tsx/12399/5

Suggestion

When counting the Cognitive Complexity, we should consider short circuits, nulls coalescing, and optional chaining as shorthand.

Propagating

• something && something.prop
• something.?prop

Coalescing

• something || other
• something ?? other

This is true for the following cases at least:

In JSX

• JSX attribute values
• JSX embedded JS expressions

Everywhere, not only in JSX

• return statements
• Assignments

Perhaps there are more cases where it makes sense.
Perhaps we don't need to count them in any place?

[saberduck]

we didn't manage to do this in current sprint, removing from milestone

[gabriel-vivas-sonarsource]

See some of the comments in #2238
As people keep coming to this subject.