support suppression of warning on import

[SethTisue]

typically the warning would be a deprecation warning

imports can't have annotations, so it would have to be via some other mechanism:

• a special comment?
• a setting where you specify what deprecated things you want to be able to import warning-free?

(opening the issue partly as documentation that there isn't any support currently)

[2m]

I have bumped into this when migrating some code that is using .mapValues from 2.12 to 2.13. Such code shows a warning with 2.13 and suggests to change to .view.mapValues. However for that one to compile with 2.12 an import scala.collection.compat._ is needed. Which is unused in 2.13 and thus shows a warning. :)

[2m]

I was able to use the warning message matching for this:

Compile / compile / scalacOptions += "-P:silencer:globalFilters=[import scala.collection.compat._]"

[SethTisue]

@ghik should this be closed, then?

[ghik]

@SethTisue why? It's as unsolved as it was in the beginning so it still serves its original "partly documentation" purpose, right?

[SethTisue]

I wasn't aware when I opened the ticket that globalFilters was applicable

[ghik]

Yeah, but it's global so it can't be used to silent each import independently.

[taig]

I was able to use the warning message matching for this:

Compile / compile / scalacOptions += "-P:silencer:globalFilters=[import scala.collection.compat._]"

Unfortunately this suppressed all warnings from files with an import scala.collection.compat._ for me.

[ghik]

@taig silencer has a test for that situation and everything looks good. Can you file a separate issue for that and provide a reproduction?

[taig]

@ghik I prepared a reproducer and checked out the project to take a deeper look and possibly submit a fix. I'm happy to share the reproduction repo and raise a new issue but I have a couple assumptions that I'd like to clarify beforehand:

• The globalFilters syntax shared in this issue ("-P:silencer:globalFilters=[import scala.collection.compat._]") appears to be wrong. From what I understand it should be a ;-delimited list of regexes. So in this case probably something like "-P:silencer:globalFilters=import scala\\.collection\\.compat\\._".

• Given that the globalFilters directive from above [import scala.collection.compat._] is treated as a regex, the contained . probably disables/filters all messages which is the issue I was seeing.

• When I look into the plugin's filter method and the msg it receives, I see an "Unused import" message, but it does not provide the second line which specifies the affected import. I therefore think that it's not possible to filter for a specific import as attempted in this issue.

[ghik]

@taig thanks a lot for your insight, it indeed looks like @2m accidentally silenced everything.

I think the solution would be to create a separate option to silence warnings based on line content.
I've created #42 for that.

[ghik]

#42 is fixed and IMO this is the best solution for suppressing unused import warnings.