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scopelint

Go Report Card CircleCI Coverage Status

scopelint checks for unpinned variables in go programs.

OBSOLETED

Use looppointer or exportloopref instead.

If you want to find lints as nervous as possible (with some false-positives), you should use looppointer.

If you want to find lints as accurately as possible (with some lints ignored), you should use exportloopref.

What's this?

Sample problem code from: https://github.com/kyoh86/scopelint/blob/master/example/readme.go

6  values := []string{"a", "b", "c"}
7  var funcs []func()
8  for _, val := range values {
9  	funcs = append(funcs, func() {
10 		fmt.Println(val)
11 	})
12 }
13 for _, f := range funcs {
14 	f()
15 }
16 /*output:
17 c
18 c
19 c
20 */
21 var copies []*string
22 for _, val := range values {
23 	copies = append(copies, &val)
24 }
25 /*(in copies)
26 &"c"
27 &"c"
28 &"c"
29 */

In Go, the val variable in the above loops is actually a single variable. So in many case (like the above), using it makes for us annoying bugs.

You can find them with scopelint, and fix it.

$ scopelint ./example/readme.go
example/readme.go:10:16: Using the variable on range scope "val" in function literal
example/readme.go:23:28: Using a reference for the variable on range scope "val"
Found 2 lint problems; failing.

(Fixed sample):

values := []string{"a", "b", "c"}
var funcs []func()
for _, val := range values {
  val := val // pin!
	funcs = append(funcs, func() {
		fmt.Println(val)
	})
}
for _, f := range funcs {
	f()
}
var copies []*string
for _, val := range values {
  val := val // pin!
	copies = append(copies, &val)
}

Install

go get -u github.com/kyoh86/scopelint

Use

Give the package paths of interest as arguments:

scopelint github.com/kyoh86/scopelint/example

To check all packages recursively in the current directory:

scopelint ./...

And also, scopelint supports the following options:

  • The --set-exit-status flag makes it to set exit status to 1 if any problem variables are found (if you DO NOT it, set --no-set-exit-status)
  • The --vendor flag enables checking in the vendor directories (if you DO NOT it, set --no-vendor flag)
  • The --test flag enables checking in the *_test.go files" (if you DO NOT it, set --no-test flag)

Nolint

To ignore issues from use an option comment like //scopelint:ignore. For example, if it's used inline (not from the beginning of the line), it ignores issues only for the line.

var copies []*string
for _, val := range values {
	copies = append(copies, &val) //scopelint:ignore
}

To ignore issues for the block of code put it on the beginning of a line before the block:

var copies []*string
//scopelint:ignore
for _, val := range values {
	copies = append(copies, &val)
}

Also, you can exclude all issues in a file by:

//scopelint:ignore
package pkg

You may add a comment explaining or justifying why //scopelint:ignore is being used on the same line as the flag itself:

//scopelint:ignore // any comment

Use with gometalinter

scopelint can be used with gometalinter in --linter flag.

gometalinter --disable-all --linter 'scope:scopelint {path}:^(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*)$'

Exit Codes

scopelint returns 1 if any problems were found in the checked files. It returns 2 if there were any other failures.

Known Issues

  • False positive for for table tests #4
    • I won't fix it because scopelint supports ignore them all. => nolint

TODO

  • Write tests
  • License (Some codes copied from golint)