v01.config accepts and applies json patch

src/device/input/parse/v01/config.go

@@ -1,5 +1,11 @@
 package v01
 
+import (
+	"encoding/json"
+
+	patch "github.com/evanphx/json-patch/v5"
+)
+
 type config struct {
 	Feedback struct {
 		Addr   string
@@ -14,3 +20,24 @@ type config struct {
 	}
 	Quiet bool
 }
+
+func (cfg config) WithJSONPatch(v interface{}) config {
+	originalData, _ := json.Marshal(cfg)
+	patchData, err := json.Marshal(v)
+	if err != nil {
+		return cfg
+	}
+	patcher, err := patch.DecodePatch(patchData)
+	if err != nil {
+		return cfg
+	}
+	patchedData, err := patcher.Apply(originalData)
+	if err != nil {
+		return cfg
+	}
+	var patched config
+	if err := json.Unmarshal(patchedData, &patched); err != nil {
+		return cfg
+	}
+	return patched
+}

src/device/input/parse/v01/config_test.go

@@ -0,0 +1,79 @@
+package v01
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestConfigPatch(t *testing.T) {
+	cases := map[string]struct {
+		cfg   config
+		patch interface{}
+		want  config
+	}{
+		"nil patch": {
+			cfg:   config{Quiet: true},
+			patch: nil,
+			want:  config{Quiet: true},
+		},
+		"[] patch": {
+			cfg:   config{Quiet: true},
+			patch: []interface{}{},
+			want:  config{Quiet: true},
+		},
+		"set fake field": {
+			cfg: config{Quiet: true},
+			patch: []interface{}{
+				map[string]interface{}{"op": "add", "path": "/Fake", "value": true},
+			},
+			want: config{Quiet: true},
+		},
+		"remove field": {
+			cfg: config{Quiet: true},
+			patch: []interface{}{
+				map[string]interface{}{"op": "remove", "path": "/Quiet"},
+			},
+			want: config{Quiet: false},
+		},
+		"replace field with valid": {
+			cfg: config{Quiet: true},
+			patch: []interface{}{
+				map[string]interface{}{"op": "replace", "path": "/Quiet", "value": false},
+			},
+			want: config{Quiet: false},
+		},
+		"replace field with invalid": {
+			cfg: config{Quiet: true},
+			patch: []interface{}{
+				map[string]interface{}{"op": "replace", "path": "/Quiet", "value": "teehee"},
+			},
+			want: config{Quiet: true},
+		},
+		"test and noop": {
+			cfg: config{Quiet: true},
+			patch: []interface{}{
+				map[string]interface{}{"op": "test", "path": "/Quiet", "value": false},
+				map[string]interface{}{"op": "replace", "path": "/Quiet", "value": false},
+			},
+			want: config{Quiet: true},
+		},
+		"test and apply": {
+			cfg: config{Quiet: true},
+			patch: []interface{}{
+				map[string]interface{}{"op": "test", "path": "/Quiet", "value": true},
+				map[string]interface{}{"op": "replace", "path": "/Quiet", "value": false},
+			},
+			want: config{Quiet: false},
+		},
+	}
+
+	for name, d := range cases {
+		c := d
+		t.Run(name, func(t *testing.T) {
+			got := c.cfg.WithJSONPatch(c.patch)
+			if fmt.Sprintf("%+v", got) != fmt.Sprintf("%+v", c.want) {
+				t.Errorf("(%+v).Patch(%+v) want %+v, got %+v", c.cfg, c.patch, c.want, got)
+			}
+		})
+	}
+}