🐛 BUG: Content-Length header missing from worker response when Content-Type present

What version of Wrangler are you using?

2.0.24

What operating system are you using?

Mac

Describe the Bug

When running wrangler dev, the Content-Length header is missing from responses if the Content-Type header is present and the Content-Length value is greater than "47".

Reproduce the bug

A list of steps to reproduce the bug.

1. Create src/index.ts:

   // src/index.ts
   export default {
     async fetch(request: Request): Promise<Response> {
       const query = new URL(request.url).searchParams;
       const contentLength = query.get("length") || "0";
       const useContentType = !query.has("no-content-type");
   
       return new Response(null, {
         headers: {
           "content-length": contentLength,
           "content-type": useContentType ? "text/plain" : "",
         },
       });
     },
   };
   

2. Run:

   wrangler dev src/index.ts
   

3. Test headers:

   curl --head "http://localhost:8787?length=47" # Should see content-length & content-type header
   curl --head "http://localhost:8787?length=48" # Will see only see content-type header
   curl --head "http://localhost:8787?length=48&no-content-type" # Will only see content-length
   

Example responses

➤ curl --head "http://localhost:8787?length=47"
HTTP/1.1 200 OK
date: Tue, 04 Oct 2022 01:56:18 GMT
content-type: text/plain
content-length: 47
report-to: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=0DzkIHu1Lq67UVp%2F3C6xjrLmoYA8hemI0R8ljz3tvi7u9myGZ%2BVkt%2FdFIeM3WKpPafwGrEAgY7H3ruK4t91qmfhDYUYH1iwZ%2Bw3z4lIESO4fP276c61m8SpV81EwTLMJGWajRXlu0IvBudGEdrjDAnI0Vt9qSEDT7tNy9r9%2F4oBG"}],"group":"cf-nel","max_age":604800}
nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
vary: Accept-Encoding
cf-ray: 754a4ce1befe8419-YVR
alt-svc: h3=":443"; ma=86400, h3-29=":443"; ma=86400
server: cloudflare
Connection: keep-alive
Keep-Alive: timeout=5

➤ curl --head "http://localhost:8787?length=48"
HTTP/1.1 200 OK
date: Tue, 04 Oct 2022 01:56:24 GMT
content-type: text/plain
report-to: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=SRSFjjRgbee0eBWHfBA7HRXPYIyWWuiXF7SjH493J7jfTz7OsdT6TskyZ%2BIR6u7F2o1Y3UtpHHKhYGnYFFEPH4bNv7JuOXQliDbRjDkfy0%2BC7KIamVJWlYB7aGXO4PxSLL24tcY1pD0RgawhKFOA%2B4Gf8SSFfrfTQgWIhWFo6MzX"}],"group":"cf-nel","max_age":604800}
nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
vary: Accept-Encoding
cf-ray: 754a4d027d628419-YVR
alt-svc: h3=":443"; ma=86400, h3-29=":443"; ma=86400
server: cloudflare
Connection: keep-alive
Keep-Alive: timeout=5

➤ curl --head "http://localhost:8787?length=48&no-content-type"
HTTP/1.1 200 OK
date: Tue, 04 Oct 2022 01:56:33 GMT
content-length: 48
report-to: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=TFg3iX90nLT%2FuAJsytKW9Y1WjbxmomkByaoO1y6lHBTgxt8YReSIXFPdpg84SMuJgziKoGgGr4gDmosML9L6%2Ft3cq7vh%2BglfWpPs9p0q8xUJncc9VJ%2FOFjtSyYpu5PHoF%2B67Omh6rwB%2FMFsZZ9sWlnqNGB%2B0%2FGObC1rLfUD0i1L5"}],"group":"cf-nel","max_age":604800}
nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
vary: Accept-Encoding
cf-ray: 754a4d3f8af18419-YVR
alt-svc: h3=":443"; ma=86400, h3-29=":443"; ma=86400
server: cloudflare
Connection: keep-alive
Keep-Alive: timeout=5

Work Around

As discovered in the Cloudflare community forum, this behaviour can be avoided by running wrangler dev with the --local flag (wrangler dev --local).

[penalosa]

I initially couldn’t reproduce it, but I think I can now trigger it intermittently. We’ll follow up internally to see what might be causing this (and thanks for the detailed reproduction steps), but in the meantime, would you be able to provide any more details on your original use case? Perhaps there’s a workaround that we could help with?

[alukach]

would you be able to provide any more details on your original use case?

My use-case is that I am developing an API that is required to send the content-length header in response to HEAD requests. Downstream clients throw errors if this header is not present in the responses.

I note that others have been able to reproduce this issue:

• https://github.com/honojs/hono/issues/577#issuecomment-1264553136
• https://community.cloudflare.com/t/content-length-header-missing-when-content-type-present/423568/2

Perhaps there’s a workaround that we could help with?

As mentioned in the original comment, this can be avoided by running Wrangler dev with the --local flag, so I’m not currently blocked.

---

I don’t think this is an emergency or top priority, but would argue that this bug:

1. demonstrates a small level of instability on the part of wrangler’s dev server, which adds to a developer’s cognitive load when developing applications with Wrangler2
2. can be a bit of a time suck for future developers who are developing applications and burn a number of hours trying to figure out why their API clients are not properly interacting with their local Wrangler-dev-hosted API.

As an aside, I will mention that my experience with Wrangler2 has been great and I’m having a fun time onboarding to Cloudflare Workers.