How to avoid annoying error declared and not used

Question

I m learning Go but I feel it is a bit annoying that when compiling  I should not leave any variable or package unused    This is really quite slowing me down  For example  I just wanted to declare a new package and plan to use it later or just uncomment some command to test  I always get the error and need to go comment all of those uses   Is there any way to avoid this kind of check in Go

User · Answer

As far as I can tell  these lines in the Go compiler look like the ones to comment out  You should be able to build your own toolchain that ignores these counterproductive warnings

User · Answer

According to the FAQ   Some have asked for a compiler option to turn those checks off or at least reduce them to warnings  Such an option has not been added  though  because compiler options should not affect the semantics of the language and because the Go compiler does not report warnings  only errors that prevent compilation  There are two reasons for having no warnings  First  if it s worth complaining about  it s worth fixing in the code   And if it s not worth fixing  it s not worth mentioning   Second  having the compiler generate warnings encourages the implementation to warn about weak cases that can make compilation noisy  masking real errors that should be fixed   I don t necessarily agree with this for various reasons not worth going into  It is what it is  and it s not likely to change in the near future  For packages  there s the goimports tool which automatically adds missing packages and removes unused ones  For example    Install it   go get golang org x tools cmd goimports    -w to write the source file instead of stdout   goimports -w my file go  You should be able to run this from any half-way decent editor - for example for Vim    goimports -w    The goimports page lists some commands for other editors  and you typically set it to be run automatically when you save the buffer to disk  Note that goimports will also run gofmt   As was already mentioned  for variables the easiest way is to  temporarily  assign them to        No errors tasty     quot ice cream quot  horrible     quot marmite quot      Commented out for debugging   eat tasty  horrible          tasty  horrible

User · Answer

I ran into this issue when I wanted to temporarily disable the sending of an email while working on another part of the code  Commenting the use of the service triggered a lot of cascade errors  so instead of commenting I used a condition if false          Technically  svc still be used so no yelling        err   svc SendRawEmail input       Check err

User · Answer

One angle not so far mentioned is tool sets used for editing the code     Using Visual Studio Code along with the Extension from lukehoban called Go will do some auto-magic for you   The Go extension automatically runs gofmt  golint etc  and removes and adds import entries  So at least that part is now automatic   I will admit its not 100  of the solution to the question  but however useful enough

User · Answer

In case others have a hard time making sense of this  I think it might help to explain it in very straightforward terms  If you have a variable that you don t use  for example a function for which you ve commented out the invocation  a common use-case    myFn    func           myFn     You can assign a useless blank variable to the function so that it s no longer unused   myFn    func            myFn    myFn

User · Answer

I ran into this while I was learning Go 2 years ago  so I declared my own function     UNUSED allows unused variables to be included in Go programs func UNUSED x    interface        And then you can use it like so  UNUSED x  UNUSED x  y  UNUSED x  y  z   The great thing about it is  you can pass anything into UNUSED  Is it better than the following            x  y  z  That s up to you

User · Answer

You can use a simple  null function  for this  for example   func Use vals    interface          for    val    range vals               val           Which you can use like so   package main  func main         a     declared and not used      b     another declared and not used      c    123      Use a  b  c      There s also a package for this so you don t have to define the Use function every time   import      github com lunux2008 xulu     func main                  xulu Use a  b  c

User · Answer

That error is here to force you to write better code  and be sure to use everything you declare or import  It makes it easier to read code written by other people  you are always sure that all declared variables will be used   and avoid some possible dead code   But  if you really want to skip this error  you can use the blank identifier        package main  import        fmt     imported and not used   fmt     func main         i    1    i declared and not used     becomes  package main  import          fmt     no more error    func main         i    1    no more error         i     As said by kostix in the comments below  you can find the official position of the Go team in the FAQ       The presence of an unused variable may indicate a bug  while unused imports just slow down compilation  Accumulate enough unused imports in your code tree and things can get very slow  For these reasons  Go allows neither

[go] How to avoid annoying error "declared and not used"

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