For completeness, I'm attaching the full stack of what happens:

1. Server hits the swagger-ui ring handler
   https://github.com/metosin/reitit/blob/master/modules/reitit-swagger-ui/src/reitit/swagger_ui.cljc#L40
2. Reitit uses response/resource-response under the hood https://github.com/metosin/reitit/blob/master/modules/reitit-ring/src/reitit/ring.cljc#L237

3. ring/ring-core/src/ring/util/response.clj

   Line 337 in bc87e3b

   (defn resource-response

4. ring/ring-core/src/ring/util/response.clj

   Line 355 in bc87e3b

   (let [response (url-response resource)]

5. ring/ring-core/src/ring/util/response.clj

   Line 313 in bc87e3b

   (defn url-response
6. And here the protocol is different:

   ring/ring-core/src/ring/util/response.clj

   Line 244 in bc87e3b

   (defmulti resource-data

GraalVM native-image produces the binary with embedded resources from jar:. They substitute the protocol with resource:, so that they can .getResource embedded in the binary.

• https://github.com/oracle/graal/blob/db22885e2deb21ff0c1a72314f7b9bb86b7d334c/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/Resources.java#L128
• https://github.com/oracle/graal/blob/db22885e2deb21ff0c1a72314f7b9bb86b7d334c/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/Resources.java#L128

Why is it important to add the following change to Ring if it's only for GraalVM?

1. Almost all of the Clojure frameworks are based on Ring. If we add the following change in the Ring we will not have to patch other libraries that use response/resource-response.
2. Without this change GraalVM returns a cryptic error on runtime.

Thanks for the patch. I think explanations of why this is included should be mainly confined to the commit message rather than as part of a comment. We can limit the comment to something like ;; GraalVM resource scheme.

Commit messages of this repository should follow the seven rules of a great Git commit message, as mentioned in the project's contributing guidelines. It looks like there's a few issues with the commit messages in this pull request:

• The commit message should not contain markdown.
• The commit message body has a line over 72 characters.

Thank you so much @weavejester. I have updated the patch. Hope the changes match Ring standards :)

BTW: Thank you for making Ring!

@weavejester Is there something I can do more to have it merged?

Apologies for the delay. I haven't had the time to setup a GraalVM environment to test this properly. Do you have an example project that uses Ring and GraalVM?

Don't sorry, it's all good! I'm patient :)

Working demo: here
Source code: here

I have included the patch in my library (see here).

How to test if patch is correct

1. Install aws, sam, bb commands. Make sure you have a docker, and at least 8GB of RAM. (if you're using mac enable 8GB in Docker Desktop).

2. Configure you AWS Account via aws configure

3. Clone the library.

4. Remove the patch.

5. Go to the examples/native/

6. You would need aws, sam, bb CLI's to deploy.

7. Run the following commands in examples/native/:

   bb hl:compile && bb hl:native:executable && sam deploy --guided

8. After deployment get the URL of the endpoint and navigate to <URL>/api-docs/index.html. It should not work without the patch.

PS: If you're using the Mac with M1 you would need to change :image in bb.edn to ghcr.io/fierycod/holy-lambda-builder:aarch64-java11-21.3.0.

Thanks for the link, but I'm looking for something a little easier to set up, and something we can keep around to test this in future (or even automate). For example, a small project that uses the Leiningen GraalVM plugin.

Hi @weavejester! Sorry for not responding for so long.

Here is the repro/example. Let me know if it's minimal enough.
I've also found this issue: #370, which I was not aware of before.

I've also prepared the configuration necessary to run Ring apps with GraalVM CE 21.3.0. See here. If you're interested in pushing it upstream, I'm happy to help with this.

This PR is not yet ready to merge. @borkdude found a corner case.
When serving a resource directory e.g. public at /public and trying to access the /public the resource-data will return an URL instead of nil.

Thanks for the heads up.

Any updates on this? It seems for now that I need to add these lines manually to every project using ring (or perhaps reitit with ring) that I want to build a native image.

Waiting for this too!

@agorgl @skynet-gh I forgot to create an issue on the GraalVM repo. I will try to find some time this week to address it, but I don't promise anything 😂