switch_to_blog() - flag for missing subsequent restore_current_blog()

[rebeccahum]

Describe the solution you'd like

From #649 (comment), it would be worth flagging that restore_current_blog() should be called subsequently (if not already).

What code should be reported as a violation?

function switch_blog() {
	$id = get_current_blog_id();

	if ( $id === 2 ) {
		return;
	}

	switch_to_blog( 2 );
}

What code should not be reported as a violation?

function switch_blog() {
	$id = get_current_blog_id();

	if ( $id === 2 ) {
		return;
	}

	switch_to_blog( 2 );
	restore_current_blog();
}

[jrfnl]

Note: while I think it would be good to add a check for this, it should be a warning and the checking for restore_current_blog() should be limited to the scope in which the call to switch_to_blog() is found.

Any such sniff will always have the potential for false positives as a plugin can have a wrapper PluginClass::restore_stuff() function declared in another file and we won't be able to trace the function calls through the code base/across files.

All the same, it is best practice to always call restore_current_blog() after a switch_to_blog() within the same function, so the fact that the sniff has the risk of false positives should not be a deterrent for creating it as the potential for bugs when the call is not made far outweighs the annoyance of false positives from a sniff.

[rebeccahum]

#649 (comment) You mentioned that you can see this being a good sniff for WPCS — is this something you'd like me to open an issue there for, @jrfnl?

[jrfnl]

@rebeccahum I wouldn't be surprised if there is an issue open for it already, but yeah, go ahead, though search in the repo first for existing issues.