Static code analysis

[Marek Kolodziej]

All, 

I was wondering if someone familiar with the current state of static analysis tools in Scala could tell me if there's, say, a Findbugs equivalent for Scala. I found that Findbugs issues many unnecessary warnings for Scala, probably having to do with the way the "object" singleton compiles to bytecode, due to traits, etc. I heard that ScalaStyle is not only a Scala version of Java's CheckStyle, that it also includes bits of Findbugs and PMD. But if it doesn't implement all of Findbugs and/or PMD, then are there other tools that supplement it? Or, is ScalaStyle good not only for style checking, but is it good for improving code quality?

Also, what about Scala's integration with, say, Sonar? Is the Scala Sonar plugin (which works with Scalastyle) reliable?

Thanks in advance for the help!

Marek

[Clint Gilbert]

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Someone posted here a few months ago about taking over development of
the Scala plugin for Sonar, but I haven't heard any more about that.
I would love more and better static analysis tools; I really miss
Sonar since switching to Scala.

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[Marek Kolodziej]

Yeah, I saw this one but I'm not sure how good either the plugin or ScalaStyle is at checking non-stylistic (Findbugs-like) issues.

Marek

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[Dennis Haupt]

not sure about the current state of it, but there are a bunch of inspection in intellij idea's scala plugin (free version)

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[Marek Kolodziej]

Right, but the issue is how to get it working as part of the build-time inspection, not in the IDE - in the sense of warning developers in case they ignored IntelliJ's recommendations, for example. I assume that IntelliJ's ideas could be reused, but I'm not quite sure if the plugin could be reused directly unless it has an API that could call it. Maybe JetBrains have the code-checking logic available separately so it could be reused for a Sonar plugin, for instance. I just don't know, hence my questions :)

Marek

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[Stephen Compall]

On Mon, 2014-03-24 at 11:32 -0700, Marek Kolodziej wrote:

I was wondering if someone familiar with the current state of static analysis tools in Scala could tell me if there's, say, a Findbugs equivalent for Scala.

You found scalastyle; here are a couple other interesting tools:

https://github.com/typelevel/wartremover#wartremover
https://opensource.plausible.coop/src/projects/SNX/repos/nx/browse (very new)

Don't forget that the compiler can turn off things very usefully, but you have to ask it to do so:
https://gist.github.com/tpolecat/8812750

Or, is ScalaStyle good not only for style checking, but is it good for improving code quality?

Many of scalastyle's style checks have nothing to do with the location of whitespace, or whether something appeared on the same line as some other thing, or whether magic numbers appeared multiple times.  Some examples:

• CovariantEqualsChecker checks that you actually implemented what you thought you were implementing.
• EqualsHashCodeChecker checks that you finished implementing that, then.
• DeprecatedJavaChecker notes that in Scala @Deprecated is deprecated in favor of @deprecated.
• NotImplementedErrorUsage points out stubs you forgot to fill in.
• NullChecker says you shouldn't use that thing that you shouldn't use, like, ever.
• PublicMethodsHaveTypeChecker sounds like a documentation problem, but following it heads off complex problems like the Product with Serializable intersection that you wouldn't discover until sometime after release, or when someone tried to use your API from Java, or when you tried a tiny, seemingly simple microoptimization.

-- Stephen Compall "^aCollection allSatisfy: [:each | aCondition]": less is better than

[Marek Kolodziej]

Hi Stephen,

This is very helpful, thanks! I also thought that ScalaStyle could probably do the job - after all CheckStyle also evolved from a formatting tool to check many more things, such as duplicated code, clone() overrides, etc. So it makes sense that ScalaStyle would do the same.

I will definitely check the other ones too.

Thanks again!

Marek

[Haoyi Li]

> DeprecatedJavaChecker notes that in Scala @Deprecated is deprecated in favor of @deprecated.

This is silly and irrational, but I thought that this line is hilarious.

Just to make my post worth reading, I'll mention my own project Acyclic, which checks that you didn't do bad things you probably didn't want to do anyway, but are incredibly easy to do. It's a pretty simple compiler plugin that you can use to start implementing your own.