diff_nonzero.go

package main

import (
	"fmt"
	"reflect"

	"github.com/google/go-cmp/cmp"
)

type Response struct {
	Meta    Meta
	Summary Summary
	Results []Result
}

type Meta struct {
	Pages int
}

type Summary struct {
	First, Last string
	Count       int
}

type Result struct {
	ID     string
	Amount int64
}

func main() {
	got := Response{
		Meta: Meta{
			Pages: 10,
		},
		Summary: Summary{
			First: "a",
			Last:  "z",
			Count: 26,
		},
		Results: []Result{
			{ID: "a", Amount: 0},
			{ID: "b", Amount: 1},
			{ID: "c", Amount: 2},
		},
	}

	fmt.Println("1", diff(got, Response{Meta: Meta{Pages: 20}}))
	fmt.Println("2", diff(got, Response{Results: []Result{{ID: "a"}, {ID: "B"}, {ID: "c"}, {ID: "d"}}}))
}

func diff(got, want Response) string {
	d := cmp.Diff(
		want, got,
		cmp.FilterPath(
			func(path cmp.Path) bool {
				wantField, _ := path[len(path)-1].Values()
				return wantField.Kind() != reflect.Invalid && wantField.IsZero()
			},
			cmp.Ignore(),
		),
	)
	if d == "" {
		return "(same)"
	}
	return "(-want +got):\n" + d
}

Output: https://go.dev/play/p/eSgea433jii

1 (-want +got):
  main.Response{
- 	Meta: main.Meta{Pages: 20},
+ 	Meta: main.Meta{Pages: 10},
  	... // 2 ignored fields
  }

2 (-want +got):
  main.Response{
  	... // 2 ignored fields
  	Results: []main.Result{
  		{ID: "a"},
  		{
- 			ID: "B",
+ 			ID: "b",
  			... // 1 ignored field
  		},
  		{ID: "c"},
- 		{ID: "d"},
  	},
  }