feat(chore): add request stale-if-error directive

cacheobject/directive.go

@@ -132,7 +132,6 @@ func parse(value string, cd cacheDirective) error {
 // time in seconds: http://tools.ietf.org/html/rfc7234#section-1.2.1
 //
 // When set to -1, this means unset.
-//
 type DeltaSeconds int32
 
 // Parser for delta-seconds, a uint31, more or less:
@@ -167,7 +166,6 @@ type cacheDirective interface {
 // LOW LEVEL API: Representation of possible request directives in a `Cache-Control` header: http://tools.ietf.org/html/rfc7234#section-5.2.1
 //
 // Note: Many fields will be `nil` in practice.
-//
 type RequestCacheDirectives struct {
 
 	// max-age(delta seconds): http://tools.ietf.org/html/rfc7234#section-5.2.1.1
@@ -188,7 +186,7 @@ type RequestCacheDirectives struct {
 	// by no more than the specified number of seconds.  If no value is
 	// assigned to max-stale, then the client is willing to accept a stale
 	// response of any age.
-	MaxStale DeltaSeconds
+	MaxStale    DeltaSeconds
 	MaxStaleSet bool
 
 	// min-fresh(delta seconds): http://tools.ietf.org/html/rfc7234#section-5.2.1.3
@@ -227,6 +225,9 @@ type RequestCacheDirectives struct {
 	// wishes to obtain a stored response.
 	OnlyIfCached bool
 
+	// stale-if-error(delta seconds): https://datatracker.ietf.org/doc/html/rfc5861#section-4
+	StaleIfError DeltaSeconds
+
 	// Extensions: http://tools.ietf.org/html/rfc7234#section-5.2.3
 	//
 	// The Cache-Control header field can be extended through the use of one
@@ -253,6 +254,8 @@ func (cd *RequestCacheDirectives) addToken(token string) error {
 		cd.NoTransform = true
 	case "only-if-cached":
 		cd.OnlyIfCached = true
+	case "stale-if-error":
+		err = ErrMaxAgeDeltaSeconds
 	default:
 		cd.Extensions = append(cd.Extensions, token)
 	}
@@ -286,6 +289,11 @@ func (cd *RequestCacheDirectives) addPair(token string, v string) error {
 		err = ErrNoTransformNoArgs
 	case "only-if-cached":
 		err = ErrOnlyIfCachedNoArgs
+	case "stale-if-error":
+		cd.StaleIfError, err = parseDeltaSeconds(v)
+		if err != nil {
+			err = ErrStaleIfErrorDeltaSeconds
+		}
 	default:
 		// TODO(pquerna): this sucks, making user re-parse
 		cd.Extensions = append(cd.Extensions, token+"="+v)
@@ -312,7 +320,6 @@ func ParseRequestCacheControl(value string) (*RequestCacheDirectives, error) {
 // LOW LEVEL API: Repersentation of possible response directives in a `Cache-Control` header: http://tools.ietf.org/html/rfc7234#section-5.2.2
 //
 // Note: Many fields will be `nil` in practice.
-//
 type ResponseCacheDirectives struct {
 
 	// must-revalidate(bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.1

cacheobject/directive_test.go

@@ -442,6 +442,13 @@ func TestNoSpacesIssue3(t *testing.T) {
 	require.Equal(t, cd.MustRevalidate, true)
 }
 
+func TestStaleIfError(t *testing.T) {
+	cd, err := ParseRequestCacheControl(`stale-if-error=999`)
+	require.NoError(t, err)
+	require.NotNil(t, cd)
+	require.Equal(t, cd.StaleIfError, DeltaSeconds(999))
+}
+
 func TestNoSpacesIssue3PrivateFields(t *testing.T) {
 	cd, err := ParseResponseCacheControl(`no-cache, no-store, private=set-cookie,hello, max-age=0, must-revalidate`)
 	require.NoError(t, err)