fix #1557

Former-commit-id: 55589069c8ed458183d28f32870fdf8f233629c6

context/compress.go

@@ -10,7 +10,7 @@ import (
 	"github.com/andybalholm/brotli"
 	"github.com/klauspost/compress/flate"
 	"github.com/klauspost/compress/gzip"
-	"github.com/klauspost/compress/s2"
+	"github.com/klauspost/compress/s2" // snappy output but likely faster decompression.
 	"github.com/klauspost/compress/snappy"
 )
 
@@ -184,11 +184,10 @@ func AcquireCompressResponseWriter(w ResponseWriter, r *http.Request, level int)
 		return nil, ErrResponseNotCompressed
 	}
 
-	encoding := negotiateAcceptHeader(acceptEncoding, []string{"gzip", "deflate", "br", "snappy", "s2"}, "")
+	encoding := negotiateAcceptHeader(acceptEncoding, []string{GZIP, DEFLATE, BROTLI, SNAPPY, S2}, IDENTITY)
 	if encoding == "" {
 		return nil, fmt.Errorf("%w: %s", ErrNotSupportedCompression, encoding)
 	}
-	AddCompressHeaders(w.Header(), encoding)
 
 	v := compressWritersPool.Get().(*CompressResponseWriter)
 	v.ResponseWriter = w
@@ -212,6 +211,8 @@ func AcquireCompressResponseWriter(w ResponseWriter, r *http.Request, level int)
 	}
 
 	v.CompressWriter = encWriter
+
+	AddCompressHeaders(w.Header(), encoding)
 	return v, nil
 }
 

context/context.go

@@ -4505,6 +4505,32 @@ func (ctx *Context) Application() Application {
 	return ctx.app
 }
 
+const errorContextKey = "iris.context.error"
+
+// SetErr is just a helper that sets an error value
+// as a context value, it does nothing more.
+// Also, by-default this error's value is written to the client
+// on failures when no registered error handler is available (see `Party.On(Any)ErrorCode`).
+// See `GetError` to retrieve it back.
+//
+// Note that, if you want to stop the chain
+// with an error see the `StopWithError` instead.
+func (ctx *Context) SetErr(err error) {
+	ctx.Values().Set(errorContextKey, err)
+}
+
+// GetErr is a helper which retrieves
+// the error value stored by `SetErr`.
+func (ctx *Context) GetErr() error {
+	if v := ctx.Values().Get(errorContextKey); v != nil {
+		if err, ok := v.(error); ok {
+			return err
+		}
+	}
+
+	return nil
+}
+
 const idContextKey = "iris.context.id"
 
 // SetID sets an ID, any value, to the Request Context.