http2: make early hints generic

PR-URL: #44820
Fixes: #44816
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Minwoo Jung <nodecorelab@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

doc/api/http.md

@@ -2124,32 +2124,41 @@ Sends an HTTP/1.1 100 Continue message to the client, indicating that
 the request body should be sent. See the [`'checkContinue'`][] event on
 `Server`.
 
-### `response.writeEarlyHints(links[, callback])`
+### `response.writeEarlyHints(hints[, callback])`
 
 <!-- YAML
 added: REPLACEME
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/44820
+    description: Allow passing hints as an object.
 -->
 
-* `links` {string|Array}
+* `hints` {Object}
 * `callback` {Function}
 
 Sends an HTTP/1.1 103 Early Hints message to the client with a Link header,
 indicating that the user agent can preload/preconnect the linked resources.
-The `links` can be a string or an array of strings containing the values
-of the `Link` header. The optional `callback` argument will be called when
+The `hints` is an object containing the values of headers to be sent with
+early hints message. The optional `callback` argument will be called when
 the response message has been written.
 
 **Example**
 
 ```js
 const earlyHintsLink = '</styles.css>; rel=preload; as=style';
-response.writeEarlyHints(earlyHintsLink);
+response.writeEarlyHints({
+  'link': earlyHintsLink,
+});
 
 const earlyHintsLinks = [
   '</styles.css>; rel=preload; as=style',
   '</scripts.js>; rel=preload; as=script',
 ];
-response.writeEarlyHints(earlyHintsLinks);
+response.writeEarlyHints({
+  'link': earlyHintsLinks,
+  'x-trace-id': 'id for diagnostics'
+});
 
 const earlyHintsCallback = () => console.log('early hints message sent');
 response.writeEarlyHints(earlyHintsLinks, earlyHintsCallback);

lib/_http_server.js

@@ -81,7 +81,8 @@ const {
 const {
   validateInteger,
   validateBoolean,
-  validateLinkHeaderValue
+  validateLinkHeaderValue,
+  validateObject
 } = require('internal/validators');
 const Buffer = require('buffer').Buffer;
 const {
@@ -301,36 +302,27 @@ ServerResponse.prototype.writeProcessing = function writeProcessing(cb) {
   this._writeRaw('HTTP/1.1 102 Processing\r\n\r\n', 'ascii', cb);
 };
 
-ServerResponse.prototype.writeEarlyHints = function writeEarlyHints(links, cb) {
+ServerResponse.prototype.writeEarlyHints = function writeEarlyHints(hints, cb) {
   let head = 'HTTP/1.1 103 Early Hints\r\n';
 
-  if (typeof links === 'string') {
-    validateLinkHeaderValue(links, 'links');
-    head += 'Link: ' + links + '\r\n';
-  } else if (ArrayIsArray(links)) {
-    if (!links.length) {
-      return;
-    }
+  validateObject(hints, 'hints');
 
-    head += 'Link: ';
+  if (hints.link === null || hints.link === undefined) {
+    return;
+  }
 
-    for (let i = 0; i < links.length; i++) {
-      const link = links[i];
-      validateLinkHeaderValue(link, 'links');
-      head += link;
+  const link = validateLinkHeaderValue(hints.link);
 
-      if (i !== links.length - 1) {
-        head += ', ';
-      }
-    }
+  if (link.length === 0) {
+    return;
+  }
 
-    head += '\r\n';
-  } else {
-    throw new ERR_INVALID_ARG_VALUE(
-      'links',
-      links,
-      'must be an array or string of format "</styles.css>; rel=preload; as=style"'
-    );
+  head += 'Link: ' + link + '\r\n';
+
+  for (const key of ObjectKeys(hints)) {
+    if (key !== 'link') {
+      head += key + ': ' + hints[key] + '\r\n';
+    }
   }
 
   head += '\r\n';

lib/internal/http2/compat.js

@@ -57,6 +57,7 @@ const {
   validateFunction,
   validateString,
   validateLinkHeaderValue,
+  validateObject,
 } = require('internal/validators');
 const {
   kSocket,
@@ -847,34 +848,21 @@ class Http2ServerResponse extends Stream {
     return true;
   }
 
-  writeEarlyHints(links) {
-    let linkHeaderValue = '';
+  writeEarlyHints(hints) {
+    validateObject(hints, 'hints');
 
-    if (typeof links === 'string') {
-      validateLinkHeaderValue(links, 'links');
-      linkHeaderValue += links;
-    } else if (ArrayIsArray(links)) {
-      if (!links.length) {
-        return;
-      }
-
-      linkHeaderValue += '';
+    const headers = ObjectCreate(null);
 
-      for (let i = 0; i < links.length; i++) {
-        const link = links[i];
-        validateLinkHeaderValue(link, 'links');
-        linkHeaderValue += link;
+    const linkHeaderValue = validateLinkHeaderValue(hints.link);
 
-        if (i !== links.length - 1) {
-          linkHeaderValue += ', ';
-        }
+    for (const key of ObjectKeys(hints)) {
+      if (key !== 'link') {
+        headers[key] = hints[key];
       }
-    } else {
-      throw new ERR_INVALID_ARG_VALUE(
-        'links',
-        links,
-        'must be an array or string of format "</styles.css>; rel=preload; as=style"'
-      );
+    }
+
+    if (linkHeaderValue.length === 0) {
+      return false;
     }
 
     const stream = this[kStream];
@@ -883,8 +871,9 @@ class Http2ServerResponse extends Stream {
       return false;
 
     stream.additionalHeaders({
+      ...headers,
       [HTTP2_HEADER_STATUS]: HTTP_STATUS_EARLY_HINTS,
-      'Link': linkHeaderValue
+      'Link': linkHeaderValue,
     });
 
     return true;

lib/internal/validators.js

@@ -403,9 +403,13 @@ function validateUnion(value, name, union) {
   }
 }
 
-function validateLinkHeaderValue(value, name) {
-  const linkValueRegExp = /^(?:<[^>]*>;)\s*(?:rel=(")?[^;"]*\1;?)\s*(?:(?:as|anchor|title)=(")?[^;"]*\2)?$/;
+const linkValueRegExp = /^(?:<[^>]*>;)\s*(?:rel=(")?[^;"]*\1;?)\s*(?:(?:as|anchor|title)=(")?[^;"]*\2)?$/;
 
+/**
+ * @param {any} value
+ * @param {string} name
+ */
+function validateLinkHeaderFormat(value, name) {
   if (
     typeof value === 'undefined' ||
     !RegExpPrototypeExec(linkValueRegExp, value)
@@ -418,6 +422,42 @@ function validateLinkHeaderValue(value, name) {
   }
 }
 
+/**
+ * @param {any} hints
+ * @return {string}
+ */
+function validateLinkHeaderValue(hints) {
+  if (typeof hints === 'string') {
+    validateLinkHeaderFormat(hints, 'hints');
+    return hints;
+  } else if (ArrayIsArray(hints)) {
+    const hintsLength = hints.length;
+    let result = '';
+
+    if (hintsLength === 0) {
+      return result;
+    }
+
+    for (let i = 0; i < hintsLength; i++) {
+      const link = hints[i];
+      validateLinkHeaderFormat(link, 'hints');
+      result += link;
+
+      if (i !== hintsLength - 1) {
+        result += ', ';
+      }
+    }
+
+    return result;
+  }
+
+  throw new ERR_INVALID_ARG_VALUE(
+    'hints',
+    hints,
+    'must be an array or string of format "</styles.css>; rel=preload; as=style"'
+  );
+}
+
 module.exports = {
   isInt32,
   isUint32,

test/parallel/test-http-early-hints-invalid-argument.js

@@ -8,7 +8,7 @@ const testResBody = 'response content\n';
 
 const server = http.createServer(common.mustCall((req, res) => {
   debug('Server sending early hints...');
-  res.writeEarlyHints('bad argument value');
+  res.writeEarlyHints('bad argument type');
 
   debug('Server sending full response...');
   res.end(testResBody);
@@ -27,7 +27,7 @@ server.listen(0, common.mustCall(() => {
   process.on('uncaughtException', (err) => {
     debug(`Caught an exception: ${JSON.stringify(err)}`);
     if (err.name === 'AssertionError') throw err;
-    assert.strictEqual(err.code, 'ERR_INVALID_ARG_VALUE');
+    assert.strictEqual(err.code, 'ERR_INVALID_ARG_TYPE');
     process.exit(0);
   });
 }));