map: Accept regex substitution in outputs (#3991)

* Replace placeholders with regex groups

* using Matcher methods

* test added

* linting fix

* Revert "linting fix"

This reverts commit cafd7296f4.

* Revert "test added"

This reverts commit 3a76cc7b0b.

* Revert "using Matcher methods"

This reverts commit cc34337b8e.

* tests added

caddytest/integration/map_test.go

@@ -19,7 +19,7 @@ func TestMap(t *testing.T) {
 
 		map {http.request.method} {dest-1} {dest-2} {
 			default unknown1    unknown2
-			~G.T    get-called
+			~G(.)(.)    G${1}${2}-called
 			POST    post-called foobar
 		}
 
@@ -30,7 +30,7 @@ func TestMap(t *testing.T) {
 	`, "caddyfile")
 
 	// act and assert
-	tester.AssertGetResponse("http://localhost:9080/version", 200, "hello from localhost get-called unknown2")
+	tester.AssertGetResponse("http://localhost:9080/version", 200, "hello from localhost GET-called unknown2")
 	tester.AssertPostResponseBody("http://localhost:9080/version", []string{}, bytes.NewBuffer([]byte{}), 200, "hello from localhost post-called foobar")
 }
 

modules/caddyhttp/map/map.go

@@ -136,6 +136,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhtt
 					if output := m.Outputs[destIdx]; output == nil {
 						continue
 					} else {
+						output = m.re.ReplaceAllString(input, m.Outputs[destIdx].(string))
 						return output, true
 					}
 				}