Add HasRetryAfter helper

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `errorsext.Retrier` configurable retry helper for any fallible operation.
 - `httpext.Retrier` configurable retry helper for HTTP requests and parsing of responses.
 - `DecodeResponseAny` non-generic helper for decoding HTTP responses.
+- `HasRetryAfter` helper for checking if a response has a `Retry-After` header and returning duration to wait.
 
 ## [5.28.1] - 2024-02-14
 ### Fixed

net/http/helpers_go1.18.go

@@ -5,9 +5,14 @@ package httpext
 
 import (
 	"errors"
-	bytesext "github.com/go-playground/pkg/v5/bytes"
 	"net/http"
+	"strconv"
 	"strings"
+	"time"
+
+	asciiext "github.com/go-playground/pkg/v5/ascii"
+	bytesext "github.com/go-playground/pkg/v5/bytes"
+	. "github.com/go-playground/pkg/v5/values/option"
 )
 
 // DecodeResponse takes the response and attempts to discover its content type via
@@ -30,3 +35,20 @@ func DecodeResponse[T any](r *http.Response, maxMemory bytesext.Bytes) (result T
 	}
 	return
 }
+
+// HasRetryAfter parses the Retry-After header and returns the duration if possible.
+func HasRetryAfter(headers http.Header) Option[time.Duration] {
+	if ra := headers.Get(RetryAfter); ra != "" {
+		if asciiext.IsDigit(ra[0]) {
+			if n, err := strconv.ParseInt(ra, 10, 64); err == nil {
+				return Some(time.Duration(n) * time.Second)
+			}
+		} else {
+			// not a number so must be a date in the future
+			if t, err := http.ParseTime(ra); err == nil {
+				return Some(time.Until(t))
+			}
+		}
+	}
+	return None[time.Duration]()
+}

net/http/retrier.go

@@ -10,7 +10,6 @@ import (
 	"strconv"
 	"time"
 
-	asciiext "github.com/go-playground/pkg/v5/ascii"
 	bytesext "github.com/go-playground/pkg/v5/bytes"
 	errorsext "github.com/go-playground/pkg/v5/errors"
 	typesext "github.com/go-playground/pkg/v5/types"
@@ -111,17 +110,8 @@ func NewRetryer() Retryer {
 
 			var sce ErrStatusCode
 			if (sce.StatusCode == http.StatusTooManyRequests || sce.StatusCode == http.StatusServiceUnavailable) && errors.As(err, &sce) && sce.Headers != nil {
-				if ra := sce.Headers.Get(RetryAfter); ra != "" {
-					if asciiext.IsDigit(ra[0]) {
-						if n, err := strconv.ParseInt(ra, 10, 64); err == nil {
-							wait = time.Duration(n) * time.Second
-						}
-					} else {
-						// not a number so must be a date in the future
-						if t, err := http.ParseTime(ra); err == nil {
-							wait = time.Until(t)
-						}
-					}
+				if ra := HasRetryAfter(sce.Headers); ra.IsSome() {
+					wait = ra.Unwrap()
 				}
 			}