http2: add headersDistinct to Http2ServerRequest fixes #64060

doc/api/http2.md

@@ -4189,6 +4189,53 @@ removeAllHeaders(request.headers);
 assert(request.url);   // Fails because the :path header has been removed
 ```
 
+#### `request.headersDistinct`
+
+<!-- YAML
+added:
+  - v18.3.0
+  - v16.17.0
+-->
+
+* Type: {Object}
+
+Similar to [`request.headers`][], but there is no join logic and the values are
+always arrays of strings, even for headers received just once.
+
+The object has a null prototype and should not be accessed using the `in`
+operator.
+
+```js
+// Prints something like:
+//
+// { 'user-agent': ['curl/7.22.0'],
+//   host: ['127.0.0.1:8000'],
+//   accept: ['*/*'] }
+console.log(request.headersDistinct);
+```
+
+<!-- YAML
+added: v8.4.0
+-->
+
+* Type: {Object}
+
+Similar to `request.headers`, but preserves duplicate header values.
+Each property is an array containing all values received for that header.
+
+The object has a null prototype and should not be accessed using the `in`
+operator.
+
+```js
+// Prints something like:
+//
+// {
+//   host: ['127.0.0.1:8000'],
+//   accept: ['text/html', 'application/json']
+// }
+console.log(request.headersDistinct);
+```
+
 #### `request.httpVersion`
 
 <!-- YAML

lib/internal/http2/compat.js

@@ -71,6 +71,7 @@ const kRawTrailers = Symbol('rawTrailers');
 const kSetHeader = Symbol('setHeader');
 const kAppendHeader = Symbol('appendHeader');
 const kAborted = Symbol('aborted');
+const kHeadersDistinct = Symbol('headersDistinct');
 
 let statusMessageWarned = false;
 let statusConnectionHeaderWarned = false;
@@ -323,6 +324,7 @@ class Http2ServerRequest extends Readable {
     this[kRawTrailers] = [];
     this[kStream] = stream;
     this[kAborted] = false;
+    this[kHeadersDistinct] = undefined;
     stream[kProxySocket] = null;
     stream[kRequest] = this;
 
@@ -356,6 +358,29 @@ class Http2ServerRequest extends Readable {
     return this[kHeaders];
   }
 
+  get headersDistinct() {
+    if (this[kHeadersDistinct] === undefined) {
+      const distinct = { __proto__: null };
+
+      const raw = this[kRawHeaders];
+
+      for (let i = 0; i < raw.length; i += 2) {
+        const name = raw[i].toLowerCase();
+        const value = raw[i + 1];
+
+        if (distinct[name] === undefined) {
+          distinct[name] = [value];
+        } else {
+          distinct[name].push(value);
+        }
+      }
+
+      this[kHeadersDistinct] = distinct;
+    }
+
+    return this[kHeadersDistinct];
+  }
+
   get rawHeaders() {
     return this[kRawHeaders];
   }

test/parallel/test-http2-compat-serverrequest-headers.js

@@ -39,6 +39,25 @@
         assert.strictEqual(rawHeaders[position + 1], value);
       }
 
+      const headersDistinct = request.headersDistinct;
+
+      assert.deepStrictEqual(
+        headersDistinct,
+        {
+          __proto__: null,
+          ':path': ['/foobar'],
+          ':method': ['GET'],
+          ':scheme': ['http'],
+          ':authority': [`localhost:${port}`],
+          'foo-bar': ['abc123'],
+        }
+      );
+
+      assert.strictEqual(
+        headersDistinct,
+        request.headersDistinct
+      );
+
       request.url = '/one';
       assert.strictEqual(request.url, '/one');