builtin: FirstNonEmpty()

builtin/builtin.go

@@ -34,17 +34,6 @@ func Pointer[T any](val T) *T {
 	return &val
 }
 
-// returns first error, or nil if no errors
-func FirstError(errs ...error) error {
-	for _, err := range errs {
-		if err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
 // helper for wrapping an error with error prefix.
 // if error is nil, nil is returned.
 func ErrorWrap(prefix string, err error) error {
@@ -63,3 +52,26 @@ func ErrorIfUnset(isUnset bool, fieldName string) error {
 		return nil
 	}
 }
+
+// returns the first non-empty value.
+func FirstNonEmpty[T comparable](values ...T) T {
+	var empty T
+	for _, value := range values {
+		if value != empty {
+			return value
+		}
+	}
+	return empty
+}
+
+// returns first error, or nil if no errors
+// Deprecated: use `FirstNonEmpty()`
+func FirstError(errs ...error) error {
+	for _, err := range errs {
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

builtin/builtin_test.go

@@ -54,3 +54,24 @@ func TestErrorIfUnset(t *testing.T) {
 	assert.Assert(t, ErrorIfUnset(false, "foo") == nil)
 	assert.EqualString(t, ErrorIfUnset(true, "foo").Error(), "'foo' is required")
 }
+
+func TestFirstNonEmptyWithString(t *testing.T) {
+	assert.EqualString(t, FirstNonEmpty("foo", "bar"), "foo")
+	assert.EqualString(t, FirstNonEmpty("", "bar"), "bar")
+	assert.EqualString(t, FirstNonEmpty(""), "")
+}
+
+func TestFirstNonEmptyWithInt(t *testing.T) {
+	var zero int
+	pi := int(314)
+
+	assert.Assert(t, FirstNonEmpty(zero, pi) == 314)
+	assert.Assert(t, FirstNonEmpty(pi, zero) == 314)
+}
+
+func TestFirstNonEmptyWithError(t *testing.T) {
+	var nilError error = nil
+	actualError := errors.New("actual")
+
+	assert.EqualString(t, FirstNonEmpty(nilError, actualError).Error(), "actual")
+}