4.x: protocol-configs does not allow h2 (http/2)

[klustria]

Environment Details

• Helidon Version: 4.x
• Helidon SE or Helidon MP
• JDK version:
• OS:
• Docker version (if applicable):

---

Problem Description

Even though http/2 is added as a dependency in the application, adding h2 in protocol-configs fails. h2 is used because it is the config-key for http/2. On the other hand, using http_1_1 to set http/1.1 config works fine.

Steps to reproduce

1. application.yaml setting:

   client:
       protocol-configs:
           http_1_1:
               max-header-size: 20000
               validate-request-headers: true
           h2:
               prior-knowledge: true
   

2. Add this in pom.xml of the project's application:

       <dependency>
           <groupId>io.helidon.webclient</groupId>
           <artifactId>helidon-webclient-http2</artifactId>
       </dependency>
   

3. And client code:

           WebClient client = WebClient.builder()
                   .baseUri(url)
                   .config(config.get("client"))
                   .build();
   

fails with:

Exception in thread "main" io.helidon.common.config.ConfigException: Unknown provider configured. Expected providers with types: [h2], but only the following providers are supported: [http_1_1], provider interface: io.helidon.webclient.spi.ProtocolConfigProvider, configured service: io.helidon.webclient.spi.ProtocolConfig

Observation

There is no Http2ProtocolConfigProvider in webclient that's why h2 does not show up as another option. Http1ProtocolConfigProvider on the other hand exists for http1 webclient

Potential Fix

1. Add Http2ProtocolConfigProvider.java in http2 module. Use Http1ProtocolConfigProvider.java as the template for this file and just replace all http1 related code with http2.
2. Add Http2ProtocolConfigProvider in module-info.java of http2 so this will be service loaded:

   ...
   import io.helidon.webclient.http2.Http2ProtocolConfigProvider;
   ...
   ...
        provides io.helidon.webclient.spi.ProtocolConfigProvider
              with Http2ProtocolConfigProvider;