Add Diff func (#20)

diff.go

@@ -0,0 +1,23 @@
+package astequal
+
+import (
+	"bytes"
+	"go/ast"
+	"go/format"
+	"go/token"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func Diff(x, y ast.Node) string {
+	var buf bytes.Buffer
+	format.Node(&buf, token.NewFileSet(), x)
+	s1 := buf.String()
+
+	buf.Reset()
+	format.Node(&buf, token.NewFileSet(), y)
+	s2 := buf.String()
+
+	// TODO(cristaloleg): replace with a more lightweight diff impl.
+	return cmp.Diff(s1, s2)
+}

go.mod

@@ -4,5 +4,6 @@ go 1.16
 
 require (
 	github.com/go-toolsmith/strparse v1.1.0
+	github.com/google/go-cmp v0.6.0
 	golang.org/x/exp/typeparams v0.0.0-20230203172020-98cc5a0785f9
 )

go.sum

@@ -2,6 +2,8 @@ github.com/go-toolsmith/astequal v1.0.3/go.mod h1:9Ai4UglvtR+4up+bAD4+hCj7iTo4m/
 github.com/go-toolsmith/strparse v1.0.0/go.mod h1:YI2nUKP9YGZnL/L1/DLFBfixrcjslWct4wyljWhSRy8=
 github.com/go-toolsmith/strparse v1.1.0 h1:GAioeZUK9TGxnLS+qfdqNbA4z0SSm5zVNtCQiyP2Bvw=
 github.com/go-toolsmith/strparse v1.1.0/go.mod h1:7ksGy58fsaQkGQlY8WVoBFNyEPMGuJin1rfoPS4lBSQ=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 golang.org/x/exp/typeparams v0.0.0-20220428152302-39d4317da171/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
 golang.org/x/exp/typeparams v0.0.0-20230203172020-98cc5a0785f9 h1:6WHiuFL9FNjg8RljAaT7FNUuKDbvMqS1i5cr2OE2sLQ=
 golang.org/x/exp/typeparams v0.0.0-20230203172020-98cc5a0785f9/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=