configure: add --enable-headers-api to enable the headers API

Defaults to disabled while labeled EXPERIMENTAL.

Make all the headers API tests require 'headers-api' to run.

configure.ac

@@ -165,6 +165,7 @@ curl_verbose_msg="enabled (--disable-verbose)"
    curl_rtmp_msg="no      (--with-librtmp)"
     curl_psl_msg="no      (--with-libpsl)"
  curl_altsvc_msg="enabled (--disable-alt-svc)"
+ curl_headers_msg="no      (--enable-headers-api)"
    curl_hsts_msg="enabled (--disable-hsts)"
     ssl_backends=
      curl_h1_msg="enabled (internal)"
@@ -3931,6 +3932,25 @@ AS_HELP_STRING([--disable-alt-svc],[Disable alt-svc support]),
        AC_MSG_RESULT(yes)
 )
 
+dnl ************************************************************
+dnl switch on/off headers-api
+dnl
+AC_MSG_CHECKING([whether to support headers-api])
+AC_ARG_ENABLE(headers-api,
+AS_HELP_STRING([--enable-headers-api],[Enable headers-api support])
+AS_HELP_STRING([--disable-headers-api],[Disable headers-api support]),
+[ case "$enableval" in
+  yes)
+       AC_MSG_RESULT(yes)
+       AC_DEFINE(USE_HEADERS_API, 1, [enable headers-api])
+       curl_headers_msg="enabled";
+       ;;
+  *) AC_MSG_RESULT(no)
+       ;;
+  esac ],
+       AC_MSG_RESULT(no)
+)
+
 dnl only check for HSTS if there's SSL present
 if test -n "$SSL_ENABLED"; then
 
@@ -4345,6 +4365,7 @@ AC_MSG_NOTICE([Configured to build curl/libcurl:
   RTMP:             ${curl_rtmp_msg}
   PSL:              ${curl_psl_msg}
   Alt-svc:          ${curl_altsvc_msg}
+  Headers API:      ${curl_headers_msg}
   HSTS:             ${curl_hsts_msg}
   HTTP1:            ${curl_h1_msg}
   HTTP2:            ${curl_h2_msg}

tests/data/test1670

@@ -30,6 +30,9 @@ Funny-head: yesyes
 #
 # Client-side
 <client>
+<features>
+headers-api
+</features>
 <server>
 http
 </server>

tests/data/test1671

@@ -33,6 +33,9 @@ Connection: close
 #
 # Client-side
 <client>
+<features>
+headers-api
+</features>
 <server>
 http
 </server>

tests/data/test1940

@@ -23,6 +23,9 @@ Location: /%TESTNUMBER0002
 
 # Client-side
 <client>
+<features>
+headers-api
+</features>
 <server>
 http
 </server>

tests/data/test1941

@@ -33,6 +33,7 @@ Silly-thing: yes yes
 <features>
 proxy
 SSL
+headers-api
 </features>
 <server>
 http

tests/data/test1942

@@ -30,6 +30,7 @@ Location: /%TESTNUMBER0002
 <client>
 <features>
 http
+headers-api
 </features>
 <server>
 http

tests/data/test1943

@@ -33,6 +33,7 @@ Server: sent-as-trailer
 <client>
 <features>
 http
+headers-api
 </features>
 <server>
 http

tests/data/test1944

@@ -33,6 +33,9 @@ Set-Cookie: 2cookie=data2;
 
 # Client-side
 <client>
+<features>
+headers-api
+</features>
 <server>
 http
 </server>

tests/data/test1945

@@ -33,6 +33,7 @@ Silly-thing: yes yes
 <features>
 proxy
 SSL
+headers-api
 </features>
 <server>
 http

tests/data/test1946

@@ -33,6 +33,9 @@ Set-Cookie: 2cookie=data2;
 
 # Client-side
 <client>
+<features>
+headers-api
+</features>
 <server>
 http
 </server>

tests/runtests.pl

@@ -2933,6 +2933,7 @@ sub setupfeatures {
     $feature{"typecheck"} = 1;
     $feature{"verbose-strings"} = 1;
     $feature{"wakeup"} = 1;
+    $feature{"headers-api"} = 1;
 
 }
 

tests/server/disabled.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -69,6 +69,9 @@ static const char *disabled[]={
 #endif
 #ifndef ENABLE_WAKEUP
   "wakeup",
+#endif
+#ifndef USE_HEADERS_API
+  "headers-api",
 #endif
   NULL
 };