feat: use del() function to ignore the member instead of assigning null

cmd/jsondiff/main_test.go

@@ -2,24 +2,25 @@ package main
 
 import (
 	"bytes"
+	"os"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
 )
 
 func Test(t *testing.T) {
 	type testCase struct {
-		name       string
-		argv       []string
-		wantStatus int
-		wantOut    string
-		wantErr    string
+		name        string
+		argv        []string
+		wantStatus  int
+		wantOutPath string
+		wantErr     string
 	}
 	testCases := []testCase{
-		{"ok; no queries", []string{"jsondiff", "../../testdata/from.json", "../../testdata/to.json"}, codeOK, "--- from.json\n+++ to.json\n@@ -1,7 +1,7 @@\n {\n   \"a\": 1,\n-  \"b\": 2,\n-  \"c\": 3,\n-  \"d\": 4\n+  \"b\": 1,\n+  \"c\": 2,\n+  \"d\": 3\n }\n \n", ""},
-		{"ok; with -exit-code", []string{"jsondiff", "-exit-code", "../../testdata/from.json", "../../testdata/to.json"}, codeHaveDifferences, "--- from.json\n+++ to.json\n@@ -1,7 +1,7 @@\n {\n   \"a\": 1,\n-  \"b\": 2,\n-  \"c\": 3,\n-  \"d\": 4\n+  \"b\": 1,\n+  \"c\": 2,\n+  \"d\": 3\n }\n \n", ""},
-		{"ok; with -only option", []string{"jsondiff", "-only", ".d", "../../testdata/from.json", "../../testdata/to.json"}, codeOK, "--- from.json\n+++ to.json\n@@ -1,2 +1,2 @@\n-4\n+3\n \n", ""},
-		{"ok; with -ignore option", []string{"jsondiff", "-ignore", ".d", "../../testdata/from.json", "../../testdata/to.json"}, codeOK, "--- from.json\n+++ to.json\n@@ -1,7 +1,7 @@\n {\n   \"a\": 1,\n-  \"b\": 2,\n-  \"c\": 3,\n+  \"b\": 1,\n+  \"c\": 2,\n   \"d\": null\n }\n \n", ""},
+		{"ok; no queries", []string{"jsondiff", "../../testdata/from.json", "../../testdata/to.json"}, codeOK, "./testdata/ok_no_queries.stdout.txt", ""},
+		{"ok; with -exit-code", []string{"jsondiff", "-exit-code", "../../testdata/from.json", "../../testdata/to.json"}, codeHaveDifferences, "./testdata/ok_with_exit_code.stdout.txt", ""},
+		{"ok; with -only option", []string{"jsondiff", "-only", ".d", "../../testdata/from.json", "../../testdata/to.json"}, codeOK, "./testdata/ok_with_only_option.stdout.txt", ""},
+		{"ok; with -ignore option", []string{"jsondiff", "-ignore", ".d", "../../testdata/from.json", "../../testdata/to.json"}, codeOK, "./testdata/ok_with_ignore_option.stdout.txt", ""},
 		{"no paths given", []string{"jsondiff"}, codeError, "", "2 file paths must be passed\n"},
 	}
 	for _, tc := range testCases {
@@ -33,11 +34,21 @@ func Test(t *testing.T) {
 			if gotStatus != tc.wantStatus {
 				t.Errorf("status code: got=%d want=%d", tc.wantStatus, gotStatus)
 			}
-			if diff := cmp.Diff(tc.wantOut, outStream.String()); diff != "" {
-				t.Errorf("output:\n%s", diff)
+			var wantOut string
+			if tc.wantOutPath != "" {
+				out, err := os.ReadFile(tc.wantOutPath)
+				if err != nil {
+					t.Fatal(err)
+				}
+				wantOut = string(out)
 			}
-			if diff := cmp.Diff(tc.wantErr, errStream.String()); diff != "" {
-				t.Errorf("error:\n%s", diff)
+			gotOut := outStream.String()
+			if diff := cmp.Diff(wantOut, gotOut); diff != "" {
+				t.Errorf("output (-want, +got):\n%s", diff)
+			}
+			gotErr := errStream.String()
+			if diff := cmp.Diff(tc.wantErr, gotErr); diff != "" {
+				t.Errorf("error (-want, +got):\n%s", diff)
 			}
 		})
 	}

cmd/jsondiff/testdata/ok_no_queries.stdout.txt

@@ -0,0 +1,13 @@
+--- from.json
++++ to.json
+@@ -1,7 +1,7 @@
+ {
+   "a": 1,
+-  "b": 2,
+-  "c": 3,
+-  "d": 4
++  "b": 1,
++  "c": 2,
++  "d": 3
+ }
+

cmd/jsondiff/testdata/ok_with_exit_code.stdout.txt

@@ -0,0 +1,13 @@
+--- from.json
++++ to.json
+@@ -1,7 +1,7 @@
+ {
+   "a": 1,
+-  "b": 2,
+-  "c": 3,
+-  "d": 4
++  "b": 1,
++  "c": 2,
++  "d": 3
+ }
+

cmd/jsondiff/testdata/ok_with_ignore_option.stdout.txt

@@ -0,0 +1,11 @@
+--- from.json
++++ to.json
+@@ -1,6 +1,6 @@
+ {
+   "a": 1,
+-  "b": 2,
+-  "c": 3
++  "b": 1,
++  "c": 2
+ }
+

cmd/jsondiff/testdata/ok_with_only_option.stdout.txt

@@ -0,0 +1,6 @@
+--- from.json
++++ to.json
+@@ -1,2 +1,2 @@
+-4
++3
+

diff.go

@@ -103,7 +103,7 @@ func Diff(from, to *Input, opts ...Option) (string, error) {
 	switch {
 	case o.ignore != nil:
 		var err error
-		q := WithUpdate(o.ignore)
+		q := deleting(o.ignore)
 		fromObj, err = ModifyValue(q, fromObj)
 		if err != nil {
 			return "", fmt.Errorf("modify(lhs): %v", err)
@@ -163,6 +163,9 @@ func toJSON(x interface{}) (string, error) {
 	return b.String(), nil
 }
 
+// WithUpdate is a internal helper function.
+//
+// Deprecated: WithUpdate will be deleted in the future.
 func WithUpdate(query *gojq.Query) *gojq.Query {
 	var ret *gojq.Query
 	qs := splitIntoTerms(query)
@@ -186,6 +189,18 @@ func WithUpdate(query *gojq.Query) *gojq.Query {
 	return ret
 }
 
+func deleting(query *gojq.Query) *gojq.Query {
+	return &gojq.Query{
+		Term: &gojq.Term{
+			Type: gojq.TermTypeFunc,
+			Func: &gojq.Func{
+				Name: "del",
+				Args: []*gojq.Query{query},
+			},
+		},
+	}
+}
+
 var nullRhs *gojq.Query
 
 func init() {

diff_test.go

@@ -72,6 +72,28 @@ func Test_withUpdate(t *testing.T) {
 	}
 }
 
+func Test_deleting(t *testing.T) {
+	queries := []struct {
+		query string
+		want  string
+	}{
+		{".age", "del(.age)"},
+		{".age, .name", "del(.age, .name)"},
+		{".age, .name, .meta", "del(.age, .name, .meta)"},
+		{".meta[]", "del(.meta[])"},
+		{".meta[0:-1]", "del(.meta[0:-1])"},
+	}
+	for _, c := range queries {
+		t.Run(c.query, func(t *testing.T) {
+			want := parseQuery(t, c.want)
+			got := deleting(parseQuery(t, c.query))
+			if diff := cmp.Diff(want, got); diff != "" {
+				t.Errorf("-want, +got:\n%s", diff)
+			}
+		})
+	}
+}
+
 func parseQuery(t *testing.T, q string) *gojq.Query {
 	t.Helper()
 	parsed, err := gojq.Parse(q)

example_test.go

@@ -69,10 +69,9 @@ func ExampleDiffFromObjects_ignore() {
 	// Output:
 	// --- from
 	// +++ to
-	// @@ -2,6 +2,6 @@
+	// @@ -1,5 +1,5 @@
+	//  {
 	//    "a": 1,
-	//    "b": null,
-	//    "c": null,
 	// -  "d": 4
 	// +  "d": 3
 	//  }