Null pointer error in play.api.libs.ws.ahc.CookieBuilder if cookie has no value

[jonaskoelker-jypo]

In my app I construct a WSRequest and call .stream() on it (this is the Scala API). It's talking to an in-house service, which responds with a Set-Cookie header with a cookie name but no cookie value. In my repro setup I use a mock response with a line saying Set-Cookie: absent-value;. In both cases I get a null pointer exception.

I tracked it down:

• When I touch the cookies I hit this:

  play-ws/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/StreamedResponse.scala

  Line 56 in d06f8b1

  override lazy val cookies: scala.collection.Seq[WSCookie] = buildCookies(headers)

• This in turns goes here:

  play-ws/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/CookieBuilder.scala

  Line 21 in d06f8b1

  Some(c) = Some(

• Since the cookie value is absent, the underlying cookie builder returns null
• Then Some(c) = Some(null) acts just like c = null (in the cookie builder)
• Then asCookie(null) is called, which tries to access (null).name which throws the null pointer exception.

I believe Some(c) = Option(<the same expression as before>) will make the null pointer exception not happen, but it's not obvious to me that this is the right design.

It's just what I did as a workaround: I made a wrapper around WSRepsonse which forwards everything to the underlying response, except it diverts the code path leading to this buggy line onto a copy-pasted-and-the-fixed version which says Option instead of Some on this line—plus some incidental and (I believe) unrelated changes.

I'm not sure what behavior to expect, given that value-free cookie headers do not conform to any HTTP standard I could find—not that I looked all day—but I definitely don't expect a null pointer exception.

Here's sbt dependencyTree | grep ws | grep -v aws | cut -f2- -d'-' | sort -u, just in case it helps. My above links are to the most recent version of each of the linked files, as far as I can find out; they look like differently indented versions of the source my LSP/metals setup jumps to.

com.typesafe.play:play-ahc-ws-standalone_2.13:2.1.7 [S]
com.typesafe.play:play-ahc-ws_2.13:2.8.11 (evicted by: 2.8.13)
com.typesafe.play:play-ahc-ws_2.13:2.8.13 [S]
com.typesafe.play:play-ws-standalone-json_2.13:2.1.7 [S]
com.typesafe.play:play-ws-standalone-xml_2.13:2.1.7 [S]
com.typesafe.play:play-ws-standalone_2.13:2.1.7 [S]
com.typesafe.play:play-ws_2.13:2.8.13 [S]

API: Scala. We also have a bit of java stuff lying around but I don't think it interacts with this bug.

OS/Java:

$ uname -a
Linux <hostname_withheld> 5.4.0-122-generic #138-Ubuntu SMP Wed Jun 22 15:00:31 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

$ java -version
openjdk version "11.0.16" 2022-07-19
OpenJDK Runtime Environment (build 11.0.16+8-post-Ubuntu-0ubuntu120.04)
OpenJDK 64-Bit Server VM (build 11.0.16+8-post-Ubuntu-0ubuntu120.04, mixed mode, sharing)