fix: Ensure conflicting flat headers in HTTP/2 are combined correctly (#4196)

pimterry · web-flow · commit bd2425052227 · 2025-05-09T10:11:17.000+02:00
diff --git a/lib/dispatcher/client-h2.js b/lib/dispatcher/client-h2.js
@@ -295,11 +295,13 @@ function writeH2 (client, request) {
     if (Array.isArray(val)) {
       for (let i = 0; i < val.length; i++) {
         if (headers[key]) {
-          headers[key] += `,${val[i]}`
+          headers[key] += `, ${val[i]}`
         } else {
           headers[key] = val[i]
         }
       }
+    } else if (headers[key]) {
+      headers[key] += `, ${val}`
     } else {
       headers[key] = val
     }
diff --git a/test/http2.js b/test/http2.js
@@ -125,8 +125,9 @@ test('Should support H2 connection (headers as array)', async t => {
   const server = createSecureServer(pem)
 
   server.on('stream', (stream, headers) => {
-    t.strictEqual(headers['x-my-header'], 'foo')
-    t.strictEqual(headers['x-my-drink'], 'coffee,tea')
+    t.strictEqual(headers['x-my-header'], 'foo, bar')
+    t.strictEqual(headers['x-my-drink'], 'coffee, tea, water')
+    t.strictEqual(headers['x-other'], 'value')
     t.strictEqual(headers[':method'], 'GET')
     stream.respond({
       'content-type': 'text/plain; charset=utf-8',
@@ -146,14 +147,20 @@ test('Should support H2 connection (headers as array)', async t => {
     allowH2: true
   })
 
-  t = tspl(t, { plan: 7 })
+  t = tspl(t, { plan: 8 })
   after(() => server.close())
   after(() => client.close())
 
   const response = await client.request({
     path: '/',
     method: 'GET',
-    headers: ['x-my-header', 'foo', 'x-my-drink', ['coffee', 'tea']]
+    headers: [
+      'x-my-header', 'foo',
+      'x-my-drink', ['coffee', 'tea'],
+      'x-my-drink', 'water',
+      'X-My-Header', 'bar',
+      'x-other', 'value'
+    ]
   })
 
   response.body.on('data', chunk => {

Original file line number	Diff line number	Diff line change
`@@ -295,11 +295,13 @@ function writeH2 (client, request) {`
`295`	`295`	`if (Array.isArray(val)) {`
`296`	`296`	`for (let i = 0; i < val.length; i++) {`
`297`	`297`	`if (headers[key]) {`
`298`		- headers[key] += `,${val[i]}`
	`298`	+ headers[key] += `, ${val[i]}`
`299`	`299`	`} else {`
`300`	`300`	`headers[key] = val[i]`
`301`	`301`	`}`
`302`	`302`	`}`
	`303`	`+ } else if (headers[key]) {`
	`304`	+ headers[key] += `, ${val}`
`303`	`305`	`} else {`
`304`	`306`	`headers[key] = val`
`305`	`307`	`}`