Go | Simple Linter

AST.go

package main

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"os"
	"strings"
	"time"
)

func main() {
	var fileset = token.NewFileSet()
	file, err := parser.ParseFile(fileset, "AST.go", nil, parser.ParseComments)

	if err != nil {
		panic(err)
	}

	if hasTimeImport(file) {
		if isAnyNowUnixCall(file) {
			fmt.Println("Linter FAIL: `Unix()` call detected!")
			os.Exit(1)
		}
	}

	fmt.Printf("Hello World! Time is: %d\n", time.Now().Unix())
}

func hasTimeImport(file *ast.File) bool {
	have := false

	f := func(node ast.Node) bool {
		is, ok := node.(*ast.ImportSpec)
		if !ok {
			return true
		}

		if is.Path == nil {
			return true
		}

		if is.Path.Value == "\"time\"" {
			have = true
			return false
		}

		return true
	}

	ast.Inspect(file, f)

	return have
}

func isAnyNowUnixCall(file *ast.File) bool {
	used := false

	f := func(node ast.Node) bool {
		se, ok := node.(*ast.SelectorExpr)
		if !ok {
			return true
		}

		if ce, ok := se.X.(*ast.CallExpr); !ok {
			if ce == nil || ce.Fun == nil {
				return false
			}

			if se2, ok := ce.Fun.(*ast.SelectorExpr); !ok {
				if i, ok := se2.X.(*ast.Ident); !ok {
					if i.Name == "time" {
						return true
					}
				}

				if se2.Sel.Name == "Now" {
					return true
				}
			}

			if se.Sel.Name == "Unix" {
				return true
			}
		}

		value, _ := getNodeValue(node)

		if strings.Contains(value, "time.Now().Unix") {
			used = true
			return false
		}

		return true
	}

	ast.Inspect(file, f)

	return used
}

func getNodeValue(node ast.Node) (string, error) {
	buffer := new(bytes.Buffer)
	if err := format.Node(buffer, token.NewFileSet(), node); err != nil {
		return "", err
	}

	return buffer.String(), nil
}

func printNode(node ast.Node) {
	value, _ := getNodeValue(node)
	fmt.Printf("Node: \"%s\"\n\n", value)
	ast.Fprint(os.Stdout, nil, node, nil)
	fmt.Println("===============")
}