feat: add nakedefer linter

[rawen17]

nakedefer is a linter that finds defer functions which return anything.
https://github.com/GaijinEntertainment/go-nakedefer

[boring-cyborg]

Hey, thank you for opening your first Pull Request !

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ ldez
❌ rawen17
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[ldez]

In order for a pull request adding a linter to be reviewed, the linter and the PR must follow some requirements.

Pull Request Description

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.golangci.reference.yml

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---

The golangci-lint team will edit this comment to check the boxes before and during the review.

This checklist does not imply that we will accept the linter.

[ldez]

Hello,

maybe I have missed something: why only defer that uses a function returning a function is a problem?

IMO using a function that returns something (not only a function) for a defer is a problem.

[xobotyi]

@ldez sometimes we're using factory for deferred functions, this linter tracks situation when deferred function returns a function and ensures that returned function is invoked, i.e. defer deferredFnFactory() would raise an error

[xobotyi]

Overall you're right, and maybe we have to make the linter stricter🤔

[rawen17]

Hello!
I\ve fixed this problem. Now defer linter сhecks that deferred call does not return anything.

[ldez]

@rawen17 you have to sign the CLA #3282 (comment)

[rawen17]

I've signed it already

[ldez]

vbuianov seems not to be a GitHub user.

The email that you are using to commit is not set up in your GitHub account, so you haven't signed.

[rawen17]

Sorry, now is signed

[Antonboom]

@rawen17, please, select more specific naming.

defer does not reflect the essence of the linter, as well as messages from it.

Moreover, it would be great to see among the examples something less abstract and closer to real life. Now it raise more questions than answers.

E.g., why is it invalid?

funcfuncDeferAnonymousReturnIntAndErr(){deferfunc() (int, error){// want "deferred call should not return anything"return1, nil }() }

If you explain more clearly the reason of the linter, I can help with the name.

Thanks 👍

[rawen17]

@Antonboom, hi!
This linter was been created to prevent cases when defer functions return any types
There are two cases:

• defer function doesn't return anything - valid for linter
• defer function returns one or more types - invalid for linter
  In this case there is a function which has defer anonymous function inside and it returns two types (int and error)
  That's why it is invalid for linter

func funcDeferAnonymousReturnIntAndErr(){defer func() (int, error){// want "deferred call should not return anything" return 1, nil }() } 

May be i misunderstood your question
If you mean why defer function must not return anything
i think, it is best practice because it error-prone cases

[Antonboom]

Okay, does the linter ignore io.Closer and other functions from popular interfaces that are usually deferred?

I propose something like:

• nakedefer (like nakedret)
• novaluedefer (like nonamedreturn)
• puredefer, cleandefer, etc.

[bombsimon]

Okay, does the linter ignore io.Closer and other functions from popular interfaces that are usually deferred?

Curious about this as well. If not, I see a lot of this pattern incoming:

deferfunc(){_, _=whatIActuallyWanted() }()

[rawen17]

In test/testdata/defer.go there are 2 examples

funcReturnErr - can be like io.Closer method Close which returns error

1. Valid for linter

func funcDeferNotReturnAnyType2(){defer func(){_ = funcReturnErr() }() } 

2. Invalid for linter

func funcDeferReturnErr(){defer funcReturnErr() // want "deferred call should not return anything" } 

[rawen17]

Change name linter 'defer' to 'nakedefer'
Add 'exclude' in config to exclude function names

[ldez]

@rawen17 can you rebase and fix the conflict?

[ldez]

@rawen17 why did you close the PR?

[rawen17]

No, it is my fault, i will try fix it
Can i open this PR again?

[ldez]

yes you can reopen this PR, but you need to add commits 😉

[rawen17]

@ldez Hello!
Can you please review this PR and tell me what i have to do for your approval?

[ldez]

Sorry for the late reply.

I share the point of view of @bombsimon maybe it can be a good idea to add io\.Close as default (only if no user configuration)

[Antonboom]

@xobotyi@rawen17 hi!

Could you please add default value for -e flag?
See comments above.

I run linter on large code base and receive warnings about:

defert.Stop() // *time.Timerdeferresponse.Body.Close() deferdb.Close() // *pg.DB

P.S. It's also cool to not ignore README badges like "Go Report", "CI Build Status", etc.

P.P.S. Could be helpful

• errcheck excludes

• golangci-lint config

--exclude-use-default Use or not use default excludes: # EXC0001 errcheck: Almost all programs ignore errors on these functions and in most cases it's ok - Error return value of .((os\.)?std(out|err)\..*|.*Close|.*Flush|os\.Remove(All)?|.*print(f|ln)?|os\.(Un)?Setenv). is not checked