Filter reactor traceback from problem responses

[yawkat]

Summary

• filter Reactor FluxOnAssembly$OnAssemblyException entries from the suppressed property in problem-json responses
• add a Kotlin regression for a suspend endpoint throwing Problem under Hooks.onOperatorDebug()
• keep the change local to ProblemJsonErrorResponseBodyProvider without adding a Reactor production dependency

Verification

• ./gradlew :test-suite-kotlin:test --tests 'io.micronaut.problem.TaskNotFoundProblemTest' --stacktrace
• ./gradlew :test-suite-serde-java:test --tests 'io.micronaut.problem.ProblemSerdeTest' :test-suite:test --tests 'io.micronaut.problem.OutOfStockTest' --stacktrace

Fixes #11817

[sonarqubecloud]

Quality Gate failed

Failed conditions
55.6% Coverage on New Code (required ≥ 70%)
1 New Bugs (required ≤ 0)

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[sdelamo]

instead of defining a d dependency, it should use the one managed in core https://github.com/micronaut-projects/micronaut-core/blob/5.0.x/gradle/libs.versions.toml#L84

[sdelamo]

Instead of defining the reactor dependency it should use Micronaut Project reactor and don't define a version.

[Copilot]

Pull request overview

Filters Reactor FluxOnAssembly$OnAssemblyException entries out of suppressed in application/problem+json responses to avoid leaking operator-debug traceback details, and adds a Kotlin regression test covering a suspend endpoint under Hooks.onOperatorDebug().

Changes:

• Filter Reactor on-assembly suppressed exceptions during Problem JSON serialization (without adding a Reactor production dependency).
• Add a Kotlin suspend /product/debug endpoint that throws a Problem to reproduce operator-debug suppressed behavior.
• Add a Kotlin regression test asserting the response does not include a suppressed field in operator debug mode.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
test-suite-kotlin/src/test/kotlin/io/micronaut/problem/TaskNotFoundProblemTest.kt	Adds regression test enabling Reactor operator debug and asserting suppressed does not leak in problem responses.
test-suite-kotlin/src/test/kotlin/io/micronaut/problem/ProductController.kt	Adds suspend /product/debug endpoint that throws a Problem to exercise the operator-debug suppressed-path.
test-suite-kotlin/build.gradle	Adds test-scope dependencies for coroutines and reactor-core needed by the new Kotlin test/controller code.
problem-json/src/main/java/io/micronaut/problem/ProblemJsonErrorResponseBodyProvider.java	Filters suppressed to drop Reactor FluxOnAssembly$OnAssemblyException and omits the field when empty.

[Copilot]

e.response.contentType.get() is used without first asserting contentType.isPresent, so if the response ever lacks a content type this test will fail with a NoSuchElementException rather than a clear assertion failure. Add an assertTrue(e.response.contentType.isPresent) (or use orElseThrow with a message) before dereferencing.

Suggested change

	Assertions.assertEquals(HttpStatus.BAD_REQUEST, e.status)
	Assertions.assertEquals(HttpStatus.BAD_REQUEST, e.status)
	Assertions.assertTrue(e.response.contentType.isPresent)

[Copilot]

The regression assertions rely on raw JSON substring matching (e.g. contains("\"type\":\"about:blank\"")), which is brittle with respect to serialization ordering/escaping and can cause flaky tests. Consider parsing the body as a map/JSON tree and asserting suppressed is absent (and that type/title/status have the expected values).

Suggested change

	client.exchange(request, String::class.java)
	}
	Assertions.assertEquals(HttpStatus.BAD_REQUEST, e.status)
	Assertions.assertEquals("application/problem+json", e.response.contentType.get().toString())
	val body = e.response.getBody(String::class.java)
	Assertions.assertTrue(body.isPresent)
	Assertions.assertTrue(body.get().contains("\"type\":\"about:blank\""))
	Assertions.assertTrue(body.get().contains("\"title\":\"Validation error\""))
	Assertions.assertTrue(body.get().contains("\"status\":400"))
	Assertions.assertFalse(body.get().contains("\"suppressed\""))
	client.exchange(request, Map::class.java)
	}
	Assertions.assertEquals(HttpStatus.BAD_REQUEST, e.status)
	Assertions.assertEquals("application/problem+json", e.response.contentType.get().toString())
	val bodyOptional = e.response.getBody(Map::class.java)
	Assertions.assertTrue(bodyOptional.isPresent)
	Assertions.assertEquals("about:blank", bodyOptional.get()["type"])
	Assertions.assertEquals("Validation error", bodyOptional.get()["title"])
	Assertions.assertEquals(400, bodyOptional.get()["status"])
	Assertions.assertFalse(bodyOptional.get().containsKey("suppressed"))

[Copilot]

This module adds new dependencies using hard-coded versions. Elsewhere in this repo test modules consistently rely on the Micronaut catalogs / version catalog (e.g. test-suite/build.gradle) to avoid version drift and unintended downgrades/upgrades. Please add these to gradle/libs.versions.toml (or use the appropriate mn... coordinates if available) and reference them via libs/catalog aliases instead of pinning versions inline.

Suggested change

	testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.10.2'
	testImplementation 'io.projectreactor:reactor-core:3.5.0'
	testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm'
	testImplementation 'io.projectreactor:reactor-core'