perf(error): better deal with deferred errors

utils/errs/errors_defer.go

@@ -0,0 +1,16 @@
+package errs
+
+import (
+	"errors"
+	"fmt"
+)
+
+// Capture runs errFunc and assigns the error, if any, to *errPtr. Preserves the
+// original error by wrapping with errors.Join if the errFunc err is non-nil.
+func Capture(errPtr *error, errFunc func() error, msg string) {
+	err := errFunc()
+	if err == nil {
+		return
+	}
+	*errPtr = errors.Join(*errPtr, fmt.Errorf("%s: %w", msg, err))
+}

utils/errs/errors_defer_test.go

@@ -0,0 +1,58 @@
+package errs
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+func TestCapture(t *testing.T) {
+	tests := []struct {
+		name     string
+		initial  error
+		errFunc  func() error
+		msg      string
+		expected string
+	}{
+		{
+			name:     "No error from errFunc",
+			initial:  nil,
+			errFunc:  func() error { return nil },
+			msg:      "test message",
+			expected: "",
+		},
+		{
+			name:     "Error from errFunc with no initial error",
+			initial:  nil,
+			errFunc:  func() error { return errors.New("error from func") },
+			msg:      "test message",
+			expected: "test message: error from func",
+		},
+		{
+			name:     "Error from errFunc with initial error",
+			initial:  errors.New("initial error"),
+			errFunc:  func() error { return errors.New("error from func") },
+			msg:      "test message",
+			expected: "initial error\ntest message: error from func",
+		},
+		{
+			name:     "Error from errFunc with initial wrapped error",
+			initial:  fmt.Errorf("wrapped error: %w", errors.New("initial error")),
+			errFunc:  func() error { return errors.New("error from func") },
+			msg:      "test message",
+			expected: "wrapped error: initial error\ntest message: error from func",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var err error = tt.initial
+			Capture(&err, tt.errFunc, tt.msg)
+			if err != nil && err.Error() != tt.expected {
+				t.Errorf("expected %q, got %q", tt.expected, err.Error())
+			} else if err == nil && tt.expected != "" {
+				t.Errorf("expected %q, got nil", tt.expected)
+			}
+		})
+	}
+}