Introduce support for truly non-blocking APIs with resteasy-reactive and mutiny (#387)

* feat(api): return response instead of void

Imagine POSTing to a resource that creates something and returns no
payload but a 201 with a Location header. Right now, there is no way to
get that url. After this commit, it
will be possible

* feat(api): support non-blocking apis

Introduce a ew config property `mutiny`, which will change the Api
classes to return `Uni<X>` instead of `X` for every method. This is
required to make truly non-blocking api calls with
quarkus-resteasy-reactive.

Of course, this requires `quarkus-resteasy-reactive` on the classpath.

* Update deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/SpecItemConfig.java

Co-authored-by: Helber Belmiro <[email protected]>

* Apply suggestions from code review

Co-authored-by: Helber Belmiro <[email protected]>

* Update deployment/src/main/resources/templates/api.qute

Co-authored-by: Helber Belmiro <[email protected]>

---------

Co-authored-by: Helber Belmiro <[email protected]>

Author: lordvlad

README.md

@@ -144,7 +144,12 @@ You can use the `quarkus-openapi-generator` with REST Client Classic or REST Cli
 </dependency>
 ```
 
-For both implementations, the generated code is always blocking code.
+To make truly non-blocking calls, you need to also set the `mutiny` option to `true`. This
+will wrap all API return types in a `io.smallrye.mutiny.Uni`.
+
+```properties
+quarkus.openapi-generator.codegen.spec.my_openapi_yaml.mutiny=true
+```
 
 When using RESTEasy Reactive:
   - The client must not declare multiple MIME-TYPES with `@Consumes`

deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/SpecItemConfig.java

@@ -75,4 +75,10 @@ public class SpecItemConfig {
      */
     @ConfigItem(name = "open-api-normalizer")
     public Map<String, String> normalizer;
+
+    /**
+     * Enable SmallRye Mutiny support. If you set this to `true`, all return types will be wrapped in `io.smallrye.mutiny.Uni`.
+     */
+    @ConfigItem(name = "mutiny")
+    public Optional<Boolean> supportMutiny;
 }

deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/OpenApiClientGeneratorWrapper.java

@@ -113,6 +113,13 @@ public OpenApiClientGeneratorWrapper withCustomRegisterProviders(String config)
         return this;
     }
 
+    public OpenApiClientGeneratorWrapper withMutiny(final Boolean config) {
+        if (config != null) {
+            configurator.addAdditionalProperty("mutiny", config);
+        }
+        return this;
+    }
+
     /**
      * Sets the global 'skipFormModel' setting. If not set this setting will default to true.
      *

deployment/src/main/resources/templates/api.qute

@@ -3,7 +3,6 @@ package {package};
 {#for imp in imports}
 import {imp.import};
 {/for}
-
 import org.eclipse.microprofile.rest.client.inject.RegisterRestClient;
 {#if hasAuthMethods || custom-register-providers.orEmpty.size > 0}
 import org.eclipse.microprofile.rest.client.annotation.RegisterProvider; 
@@ -83,10 +82,18 @@ public interface {classname} {
     @org.eclipse.microprofile.faulttolerance.CircuitBreaker
     {/if}{/for}
     {/if}{/for}
-        {#if return-response}
-    public jakarta.ws.rs.core.Response {op.nickname}(
+        {#if mutiny}
+            {#if return-response}
+    public io.smallrye.mutiny.Uni<jakarta.ws.rs.core.Response> {op.nickname}(
+            {#else}
+    public {#if op.returnType}io.smallrye.mutiny.Uni<{op.returnType}>{#else}io.smallrye.mutiny.Uni<jakarta.ws.rs.core.Response>{/if} {op.nickname}(
+            {/if}
         {#else}
+            {#if return-response}
+    public jakarta.ws.rs.core.Response {op.nickname}(
+            {#else}
     public {#if op.returnType}{op.returnType}{#else}jakarta.ws.rs.core.Response{/if} {op.nickname}(
+            {/if}
         {/if}
         {#if op.hasFormParams}
         {#if is-resteasy-reactive}

deployment/src/test/java/io/quarkiverse/openapi/generator/deployment/wrapper/OpenApiClientGeneratorWrapperTest.java

@@ -387,6 +387,28 @@ void withoutAnyTypeOrImportMappingsItShouldGenerateUsingJava8DatesAndTimes()
                 .contains("java.time.LocalDate", "java.time.OffsetDateTime");
     }
 
+    @Test
+    void shouldBeAbleToEnableMutiny() throws URISyntaxException, FileNotFoundException {
+        List<File> generatedFiles = createGeneratorWrapper("simple-openapi.json")
+                .withMutiny(true)
+                .generate("org.mutiny.enabled");
+
+        Optional<File> file = generatedFiles.stream()
+                .filter(f -> f.getName().endsWith("DefaultApi.java"))
+                .findAny();
+        assertThat(file).isNotEmpty();
+        CompilationUnit compilationUnit = StaticJavaParser.parse(file.orElseThrow());
+        List<MethodDeclaration> methodDeclarations = compilationUnit.findAll(MethodDeclaration.class);
+        assertThat(methodDeclarations).isNotEmpty();
+
+        methodDeclarations.forEach(m -> {
+            var returnType = m.getType().toString();
+            assertTrue(returnType.startsWith("io.smallrye.mutiny.Uni<"));
+            assertTrue(returnType.endsWith(">"));
+        });
+
+    }
+
     @Test
     void shouldBeAbleToAddCustomDateAndTimeMappings() throws URISyntaxException, FileNotFoundException {
         List<File> generatedFiles = createGeneratorWrapper("datetime-regression.yml")