pkg/osutil: add Read/ParseJSON functions

2 files changed, 40 insertions, 0 deletions

diff --git a/pkg/osutil/osutil.go b/pkg/osutil/osutil.go
index 1379e8c23..936465ee7 100644
--- a/pkg/osutil/osutil.go
+++ b/pkg/osutil/osutil.go
@@ -268,6 +268,25 @@ func WriteJSON[T any](filename string, obj T) error {
 	return WriteFile(filename, jsonData)
 }
 
+func ReadJSON[T any](filename string) (T, error) {
+	data, err := os.ReadFile(filename)
+	if err != nil {
+		var v T
+		return v, err
+	}
+	return ParseJSON[T](data)
+}
+
+func ParseJSON[T any](data []byte) (T, error) {
+	dec := json.NewDecoder(bytes.NewReader(data))
+	dec.DisallowUnknownFields()
+	var v T
+	if err := dec.Decode(&v); err != nil {
+		return v, fmt.Errorf("failed to unmarshal %T: %w", v, err)
+	}
+	return v, nil
+}
+
 func WriteGzipStream(filename string, reader io.Reader) error {
 	f, err := os.Create(filename)
 	if err != nil {
diff --git a/pkg/osutil/osutil_test.go b/pkg/osutil/osutil_test.go
index 7d5913b4a..4d9bf4cf8 100644
--- a/pkg/osutil/osutil_test.go
+++ b/pkg/osutil/osutil_test.go
@@ -10,6 +10,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestIsExist(t *testing.T) {
@@ -129,3 +131,22 @@ func TestMonotonicNano(t *testing.T) {
 		t.Fatalf("diff %v", diff)
 	}
 }
+
+func TestReadWriteJSON(t *testing.T) {
+	type Test struct {
+		X int
+		Y string
+	}
+	test := Test{10, "foo"}
+	file := filepath.Join(t.TempDir(), "file")
+	if err := WriteJSON(file, test); err != nil {
+		t.Fatal(err)
+	}
+	test2, err := ReadJSON[Test](file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if diff := cmp.Diff(test, test2); diff != "" {
+		t.Fatal(diff)
+	}
+}