A linter is an automatic tool to analyze code and catch errors.
To understand why linters are important, let’s take one concrete example. In mistake #1, “Unintended variable shadowing,” we discussed potential errors related to variable shadowing. Using vet, a standard linter from the Go toolset, and shadow, we can detect shadowed variables:
package main
import "fmt"
func main() {
i := 0
if true {
i := 1
fmt.Println(i)
}
fmt.Println(i)
}
Because vet is included with the Go binary, let’s first install shadow, link it with Go vet, and then run it on the previous example:
zzh@ZZHPC:/zdata/Github/ztest$ go install golang.org/x/tools/go/analysis/passes/shadow/cmd/shadow@latest go: downloading golang.org/x/tools v0.18.0 go: downloading golang.org/x/mod v0.15.0 zzh@ZZHPC:/zdata/Github/ztest$ go vet -vettool $(which shadow) # github.com/ZhangZhihuiAAA/ztest ./main.go:8:9: declaration of "i" shadows declaration at line 6
As we can see, vet informs us that the variable i is shadowed in this example. Using appropriate linters can help make our code more robust and detect potential errors.
NOTE that 'go vet' is a different tool with 'go tool vet':
zzh@ZZHPC:/zdata/Github/ztest$ go tool vet vet is a tool for static analysis of Go programs. Usage of vet: vet unit.cfg # execute analysis specified by config file vet help # general help, including listing analyzers and flags vet help name # help on specific analyzer and its flags
Here is a list that you may want to use daily:
https://golang.org/cmd/vet/—A standard Go analyzer
https://github.com/kisielk/errcheck—An error checker
https://github.com/fzipp/gocyclo—A cyclomatic complexity analyzer
https://github.com/jgautheron/goconst—A repeated string constants analyzer
Besides linters, we should also use code formatters to fix code style. Here is a list of some code formatters for you to try:
https://golang.org/cmd/gofmt/—A standard Go code formatter
https://godoc.org/golang.org/x/tools/cmd/goimports—A standard Go imports formatter
Meanwhile, we should also look at golangci-lint (https://github.com/golangci/golangci-lint). It’s a linting tool that provides a facade on top of many useful linters and formatters. Also, it allows running the linters in parallel to improve analysis speed, which is quite handy.