golang自定义linter

linter的原理是通过静态代码分析,发现其中隐藏的错误或者不符合规范的地方,然后给暴露出来,提升系统的稳定性。linter扫描的过程如下：首先进行词法分析得到一系列token,然后通过语法分析得到抽象语法树,接着通过inspector或者visitor模式提取我们感兴趣的语法单元,结合我们的规范,对比发现其中的差异,将差异暴露出来。

那么如何定义一个linter呢,首先我们从一个简单的demo开始,目标是扫描出函数第一个参数不是context.Context的函数,它可以作为我们代码提交后的lint工具。demo如下:

package main

import(

"fmt"

)

func add(a, b int) int {

return a + b

}

func main() {

add(1, 2)

fmt.Println(add(1, 2))

}

我们的的linter可以简单这么实现

package main

import (

"fmt"

"go/ast"

"go/parser"

"go/token"

"log"

"os"

)

func main() {

v := visitor{fset: token.NewFileSet()}

for _, filePath := range os.Args[1:] {

if filePath == "--" { // to be able to run this like "go run main.go -- input.go"

continue

}

f, err := parser.ParseFile(v.fset, filePath, nil, 0)

if err != nil {

log.Fatalf("Failed to parse file %s: %s", filePath, err)

}

ast.Walk(&v, f)

}

}

type visitor struct {

fset *token.FileSet

}

func (v *visitor) Visit(node ast.Node) ast.Visitor {

funcDecl, ok := node.(*ast.FuncDecl)

if !ok {

return v

}

params := funcDecl.Type.Params.List // get params

// list is equal of zero that don't need to checker.

if len(params) == 0 {

return v

}

firstParamType, ok := params[0].Type.(*ast.SelectorExpr)

if ok && firstParamType.Sel.Name == "Context" {

return v

}

fmt.Printf("%s: %s function first params should be Context\n",

v.fset.Position(node.Pos()), funcDecl.Name.Name)

return v

}

通过visitor模式,获取函数的第一个参数,判断类型不是我们需要的类型,就报错。执行结果如下：

% go run ./json/linter/exp1/main.go -- ./json/linter/demo/main.go

./json/linter/demo/main.go:4:1: add function first params should be Context

上述过程虽然能够满足我们的需求,但是,没法集成到通用的linter工具里面,我们可以使用golang官方的包"golang.org/x/tools/go/analysis"进行实现

package firstparamcontext

`

import (

"go/ast"

"golang.org/x/tools/go/analysis"

)

var Analyzer = &analysis.Analyzer{

Name: "firstparamcontext",

Doc: "Checks that functions first param type is Context",

Run: run,

}

func run(pass *analysis.Pass) (interface{}, error) {

inspect := func(node ast.Node) bool {

funcDecl, ok := node.(*ast.FuncDecl)

if !ok {

return true

}

params := funcDecl.Type.Params.List // get params

// list is equal of zero that don't need to checker.

if len(params) == 0 {

return true

}

firstParamType, ok := params[0].Type.(*ast.SelectorExpr)

if ok && firstParamType.Sel.Name == "Context" {

return true

}

pass.Reportf(node.Pos(), "''%s' function first params should be Context\n",

funcDecl.Name.Name)

return true

}

for _, f := range pass.Files {

ast.Inspect(f, inspect)

}

return nil, nil

}

然后用signlechecker来验证下它的功能

package main

import (

"golang.org/x/tools/go/analysis/singlechecker"

"learn/json/linter/exp2/firstparamcontext"

)

func main() {

singlechecker.Main(firstparamcontext.Analyzer)

}

执行结果如下：

% go run ./json/linter/exp2/main.go -- ./json/linter/demo/main.go

/Users/xiazemin/bilibili/live/learn/json/linter/demo/main.go:4:1: ''add' function first params should be Context

exit status 3

我们一般是使用https://github.com/golangci/golangci-lint来实现代码扫描的,我们的linter工具如何集成到golangci-lint里面呢?

首先,我们可以定义好linter工具

package firstparamcontext

import (

"go/ast"

"golang.org/x/tools/go/analysis"

)

var Analyzer = &analysis.Analyzer{

Name: "firstparamcontext",

Doc: "Checks that functions first param type is Context",

Run: run,

}

func run(pass *analysis.Pass) (interface{}, error) {

inspect := func(node ast.Node) bool {

funcDecl, ok := node.(*ast.FuncDecl)

if !ok {

return true

}

params := funcDecl.Type.Params.List // get params

// list is equal of zero that don't need to checker.

if len(params) == 0 {

return true

}

firstParamType, ok := params[0].Type.(*ast.SelectorExpr)

if ok && firstParamType.Sel.Name == "Context" {

return true

}

pass.Reportf(node.Pos(), "''%s' function first params should be Context\n",

funcDecl.Name.Name)

return true

}

for _, f := range pass.Files {

ast.Inspect(f, inspect)

}

return nil, nil

}

然后在golang-cli仓库中pkg/golinters目录下引入我们的linter

package golinters

import (

"golang.org/x/tools/go/analysis"

"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"

"github.com/xiazemin/firstparamcontext"

)

func NewfirstparamcontextCheck() *goanalysis.Linter {

return goanalysis.NewLinter(

"firstparamcontext",

"Checks that functions first param type is Context",

[]*analysis.Analyzer{firstparamcontext.Analyzer},

nil,

).WithLoadMode(goanalysis.LoadModeSyntax)

}

紧接着在learn/json/linter/golangci-lint/pkg/lint/lintersdb/manager.go中引入,否则在命令行中看不到

lcs := []*linter.Config{

linter.NewConfig(golinters.NewfirstparamcontextCheck()).

WithSince("0.0.0").

WithPresets(linter.PresetBugs).

WithLoadForGoAnalysis().

WithURL("github.com/xiazemin/firstparamcontext"),

然后进行编译,注意把makefile里面//export GOPROXY = https://proxy.golang.org替换为//export GOPROXY = https://proxy.cn

cd golangci-lint

% make

或者

go build -o golangci-lint ./cmd/golangci-lint

然后到我们的demo目录下测验下

% ../golangci-lint/golangci-lint linters

// Disabled by your configuration linters:

// firstparamcontext: Checks that functions first param type is Context [fast: false, auto-fix: false]

查看下lint结果

```

% ../golangci-lint/golangci-lint run -E firstparamcontext

main.go:8:1: ''add' function first params should be Context (firstparamcontext)

func add(a, b int) int {

^

main.go:13:2: SA4017: add doesn't have side effects and its return value is ignored (staticcheck)

add(1, 2)

^

```