`avoid_catches_without_on_clauses` false positives

[Hixie]

One valid use for catching all exceptions and errors is to forward them to some error reporting logic, for example, the way that Flutter frequently catches all exceptions and forwards them to FlutterError.reportError.

It would be nice if a function like FlutterError.reportError could be annotated as a valid reason to catch exceptions, such that if the catch block contains a call to such a function, it isn't flagged with avoid_catches_without_on_clauses.

[Hixie]

Forwarding to Completer.completeError would be another example of a valid reason to catch all exceptions.

[Hixie]

Another example of a false positive is catch blocks that unconditionally call rethrow.

[Hixie]

Another false positive is when a new exception is thrown, wrapping the original one.

[Hixie]

Another false positive is when the catch block does return Future.error with the exception.

[bwilkerson]

How common are the false positive cases? Would it be better to fix them all, or to just stop using it?

[Hixie]

It did catch some problems, so it has value. flutter/flutter#91642 is the PR where I'm trying to turn it on (along with a few other lints), if you want to take a look.

[bwilkerson]

I wonder whether there's a better way to formulate the lint (something other than "don't do this broad thing except in these 5 cases"). Maybe one or more specific use cases that should unconditionally be avoided.

[Hixie]

The two problems I personally care about catching here are (1) cases where people willy-nilly swallow all exceptions because they just want to push all problems under the carpet, and (2) cases where someone wants to catch a specific exception but casts a much wider net than necessary (e.g. they just need to catch FormatException but they actually catch everything). Because Flutter is a framework it also does a lot of passing exceptions around, but I think that's pretty uncommon in apps.

[Hixie]

FWIW, due to the number of false positives, we've decided in flutter/flutter#91642 to disable the lint for Flutter's framework for now, but if we can ever enable it without all the //ignores I would be very happy because it catches some insidious patterns that a lot of people (including me) accidentally use and that are very hard to fix after the fact.