move logic into compat.js

lib/internal/http2/compat.js

@@ -47,6 +47,7 @@ const {
 } = constants;
 
 let statusMessageWarned = false;
+const statusHeaderMessageWarned = {};
 
 // Defines and implements an API compatibility layer on top of the core
 // HTTP/2 implementation, intended to provide an interface that is as
@@ -60,6 +61,9 @@ function assertValidHeader(name, value) {
     err = new ERR_HTTP2_PSEUDOHEADER_NOT_ALLOWED();
   } else if (value === undefined || value === null) {
     err = new ERR_HTTP2_INVALID_HEADER_VALUE(value, name);
+  } else if (name === constants.HTTP2_HEADER_CONNECTION) {
+    headerMessageWarn(name);
+    value = '';
   }
   if (err !== undefined) {
     Error.captureStackTrace(err, assertValidHeader);
@@ -90,6 +94,18 @@ function statusMessageWarn() {
   }
 }
 
+function headerMessageWarn(key) {
+  if (!statusHeaderMessageWarned[key] ||
+      statusHeaderMessageWarned[key] === false) {
+    process.emitWarning(
+      `The provided header "${key}" is not valid, ` +
+      'and is supported only for compatibility.',
+      'UnsupportedWarning'
+    );
+    statusHeaderMessageWarned[key] = true;
+  }
+}
+
 function onStreamData(chunk) {
   const request = this[kRequest];
   if (request !== undefined && !request.push(chunk))

lib/internal/http2/util.js

@@ -387,6 +387,7 @@ function getStreamState(stream) {
 
 function isIllegalConnectionSpecificHeader(name, value) {
   switch (name) {
+    case HTTP2_HEADER_CONNECTION:
     case HTTP2_HEADER_UPGRADE:
     case HTTP2_HEADER_HOST:
     case HTTP2_HEADER_HTTP2_SETTINGS:
@@ -479,8 +480,6 @@ function mapToHeaders(map,
           ret += `${key}\0${val}\0`;
         }
         count += value.length;
-      } else if (key === HTTP2_HEADER_CONNECTION) {
-        headerMessageWarn(key);
       } else {
         ret += `${key}\0${value}\0`;
         count++;
@@ -586,14 +585,6 @@ function sessionName(type) {
   }
 }
 
-function headerMessageWarn(key) {
-  process.emitWarning(
-    `The provided header "${key}" is not valid, ` +
-    'and is supported only for compatibility.',
-    'UnsupportedWarning'
-  );
-}
-
 module.exports = {
   assertIsObject,
   assertValidPseudoHeaderResponse,