astequal

README

astequal

Package astequal provides AST (deep) equallity check operations.

Installation:

go get github.com/go-toolsmith/astequal

Example

package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"log"
	"reflect"

	"github.com/go-toolsmith/astequal"
)

func main() {
	const code = `
		package foo

		func main() {
			x := []int{1, 2, 3}
			x := []int{1, 2, 3}
		}`

	fset := token.NewFileSet()
	pkg, err := parser.ParseFile(fset, "string", code, 0)
	if err != nil {
		log.Fatalf("parse error: %+v", err)
	}

	fn := pkg.Decls[0].(*ast.FuncDecl)
	x := fn.Body.List[0]
	y := fn.Body.List[1]

	// Reflect DeepEqual will fail due to different Pos values.
	// astequal only checks whether two nodes describe AST.
	fmt.Println(reflect.DeepEqual(x, y)) // => false
	fmt.Println(astequal.Node(x, y))     // => true
	fmt.Println(astequal.Stmt(x, y))     // => true
}

Performance

astequal outperforms reflection-based comparison by a big margin:

BenchmarkEqualExpr/astequal.Expr-8       5000000     298 ns/op       0 B/op   0 allocs/op
BenchmarkEqualExpr/astequal.Node-8       3000000     409 ns/op       0 B/op   0 allocs/op
BenchmarkEqualExpr/reflect.DeepEqual-8     50000   38898 ns/op   10185 B/op   156 allocs/op

Documentation

Overview

Package astequal provides AST (deep) equallity check operations.

Example

package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"log"
	"reflect"

	"github.com/go-toolsmith/astequal"
)

func main() {
	const code = `
		package foo

		func main() {
			x := []int{1, 2, 3}
			x := []int{1, 2, 3}
		}`

	fset := token.NewFileSet()
	pkg, err := parser.ParseFile(fset, "string", code, 0)
	if err != nil {
		log.Fatalf("parse error: %+v", err)
	}

	fn := pkg.Decls[0].(*ast.FuncDecl)
	x := fn.Body.List[0]
	y := fn.Body.List[1]

	// Reflect DeepEqual will fail due to different Pos values.
	// astequal only checks whether two nodes describe AST.
	fmt.Println(reflect.DeepEqual(x, y)) // => false
	fmt.Println(astequal.Node(x, y))     // => true
	fmt.Println(astequal.Stmt(x, y))     // => true

}

Output:
false
true
true

Index

• func Decl(x, y ast.Decl) bool
• func Expr(x, y ast.Expr) bool
• func Node(x, y ast.Node) bool
• func Stmt(x, y ast.Stmt) bool

Examples

• Package

Functions

func Decl

func Decl(x, y ast.Decl) bool

Decl reports whether two AST declarations are structurally (deep) equal.

Nil arguments are permitted: true is returned if x and y are both nils. ast.BadDecl comparison always yields false.

func Expr

func Expr(x, y ast.Expr) bool

Expr reports whether two AST expressions are structurally (deep) equal.

Nil arguments are permitted: true is returned if x and y are both nils. ast.BadExpr comparison always yields false.

func Node

func Node(x, y ast.Node) bool

Node reports whether two AST nodes are structurally (deep) equal.

Nil arguments are permitted: true is returned if x and y are both nils.

See also: Expr, Stmt, Decl functions.

func Stmt

func Stmt(x, y ast.Stmt) bool

Stmt reports whether two AST statements are structurally (deep) equal.

Nil arguments are permitted: true is returned if x and y are both nils. ast.BadStmt comparison always yields false.