encode: Drop prefer from Caddyfile (#4156)

Followup to #4150, #4151 /cc @ueffel @polarathene

After a bit of discussion with @mholt, we decided to remove `prefer` as a subdirective and just go with using the order implicitly always. Simpler config, simpler docs, etc.

Effectively changes 7776471 and reverts a small part of f35a7fa.

caddytest/integration/caddyfile_adapt/encode_options.txt

@@ -3,7 +3,6 @@
 # All the options
 encode gzip zstd {
 	minimum_length 256
-	prefer zstd gzip
 	match {
 		status 2xx 4xx 500
 		header Content-Type text/*
@@ -16,18 +15,10 @@ encode gzip zstd {
 	}
 }
 
-# Prefer list is implied (short way)
-encode gzip zstd
-
-# Prefer list is implied (long way)
+# Long way with a block for each encoding
 encode {
-	gzip 5
 	zstd
-}
-
-# Prefer list is turned off
-encode gzip zstd {
-	prefer off
+	gzip 5
 }
 ----------
 {
@@ -66,17 +57,6 @@ encode gzip zstd {
 										]
 									},
 									"minimum_length": 256,
-									"prefer": [
-										"zstd",
-										"gzip"
-									]
-								},
-								{
-									"encodings": {
-										"gzip": {},
-										"zstd": {}
-									},
-									"handler": "encode",
 									"prefer": [
 										"gzip",
 										"zstd"
@@ -91,16 +71,9 @@ encode gzip zstd {
 									},
 									"handler": "encode",
 									"prefer": [
-										"gzip",
-										"zstd"
+										"zstd",
+										"gzip"
 									]
-								},
-								{
-									"encodings": {
-										"gzip": {},
-										"zstd": {}
-									},
-									"handler": "encode"
 								}
 							]
 						}

modules/caddyhttp/encode/caddyfile.go

@@ -43,7 +43,6 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 //         gzip           [<level>]
 //         zstd
 //         minimum_length <length>
-//         prefer         off|<formats...>
 //         # response matcher block
 //         match {
 //             status <code...>
@@ -55,8 +54,7 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 //
 // Specifying the formats on the first line will use those formats' defaults.
 func (enc *Encode) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
-	var preferDefaults []string
-	var preferOff bool
+	var prefer []string
 
 	responseMatchers := make(map[string]caddyhttp.ResponseMatcher)
 
@@ -74,7 +72,7 @@ func (enc *Encode) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 				enc.EncodingsRaw = make(caddy.ModuleMap)
 			}
 			enc.EncodingsRaw[arg] = caddyconfig.JSON(encoding, nil)
-			preferDefaults = append(preferDefaults, arg)
+			prefer = append(prefer, arg)
 		}
 
 		for d.NextBlock(0) {
@@ -88,20 +86,6 @@ func (enc *Encode) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 					return err
 				}
 				enc.MinLength = minLength
-			case "prefer":
-				var encs []string
-				for d.NextArg() {
-					// if one of the values is "off", then
-					// we'll skip setting the prefer list.
-					if d.Val() == "off" {
-						preferOff = true
-					}
-					encs = append(encs, d.Val())
-				}
-				if len(encs) == 0 {
-					return d.ArgErr()
-				}
-				enc.Prefer = encs
 			case "match":
 				err := caddyhttp.ParseNamedResponseMatcher(d.NewFromNextSegment(), responseMatchers)
 				if err != nil {
@@ -124,22 +108,13 @@ func (enc *Encode) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 					enc.EncodingsRaw = make(caddy.ModuleMap)
 				}
 				enc.EncodingsRaw[name] = caddyconfig.JSON(encoding, nil)
-				preferDefaults = append(preferDefaults, name)
+				prefer = append(prefer, name)
 			}
 		}
 	}
 
-	// if the "prefer" subdirective wasn't specified, use
-	// the order in which the encoders were defined.
-	if len(enc.Prefer) == 0 {
-		enc.Prefer = preferDefaults
-	}
-
-	// if "prefer off" was set, then we'll not use the default
-	// behaviour of the order in which they were defined.
-	if preferOff {
-		enc.Prefer = nil
-	}
+	// use the order in which the encoders were defined.
+	enc.Prefer = prefer
 
 	return nil
 }