ReactorDebugAgentTest.java

/*
 * Copyright (c) 2019-2022 VMware Inc. or its affiliates, All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package reactor.tools.agent;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Iterator;
import java.util.function.Function;
import java.util.stream.Stream;

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.NoOp;
import org.junit.jupiter.api.Test;

import reactor.core.CoreSubscriber;
import reactor.core.Scannable;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import static org.assertj.core.api.Assertions.assertThat;

public class ReactorDebugAgentTest {

	static {
		ReactorDebugAgent.init();

		// Since ReactorDebugAgentTest is already loaded, we need to re-process it
		ReactorDebugAgent.processExistingClasses();
	}

	@Test
	public void shouldAddAssemblyInfo() {
		int baseline = getBaseline();
		Flux<Integer> flux = Flux.just(1);

		assertThat(Scannable.from(flux).stepName())
				.startsWith("Flux.just ⇢ at reactor.tools.agent.ReactorDebugAgentTest.shouldAddAssemblyInfo(ReactorDebugAgentTest.java:" + (baseline + 1));
	}

	@Test
	public void shouldWorkWithMethodChains() {
		int baseline = getBaseline();
		Flux<Integer> flux = Flux.just(1).map(it -> it);

		assertThat(Scannable.from(flux).stepName())
				.startsWith("Flux.map ⇢ at reactor.tools.agent.ReactorDebugAgentTest.shouldWorkWithMethodChains(ReactorDebugAgentTest.java:" + (baseline + 1));
	}

	@Test
	public void shouldNotAddToCheckpoint() {
		Flux<Integer> flux = Flux.just(1).checkpoint("foo");

		assertThat(Scannable.from(flux).stepName())
				.isEqualTo("checkpoint(\"foo\")");
	}

	@Test
	public void shouldInstrumentReturns() {
		Mono<Integer> mono = methodReturningMono(Mono.just(1));

		assertThat(Scannable.from(mono).stepName())
				.startsWith("at reactor.tools.agent.ReactorDebugAgentTest.methodReturningMono(ReactorDebugAgentTest.java:" + (methodReturningMonoBaseline + 2));
	}

	@Test
	public void shouldWorkWithGroupedFlux() {
		int baseline = getBaseline();
		Flux<Integer> flux = Flux.just(1).groupBy(it -> it).blockFirst().map(Function.identity());

		assertThat(Scannable.from(flux).stepName())
				.startsWith("GroupedFlux.map ⇢ at reactor.tools.agent.ReactorDebugAgentTest.shouldWorkWithGroupedFlux(ReactorDebugAgentTest.java:" + (baseline + 1));
	}

	@Test
	public void shouldHandleNullReturnValue() {
		Mono<Integer> mono = methodReturningNullMono();

		assertThat(mono).isNull();
	}

	@Test
	public void stackTrace() {
		StringWriter sw = new StringWriter();
		int baseline = getBaseline();
		Mono.just(5)
				.map(i -> i < 3 ? i : null)
				.as(this::methodReturningMono)
				.onErrorResume(t -> {
					t.printStackTrace();
					t.printStackTrace(new PrintWriter(sw));
					return Mono.empty();
				})
				.block();

		String debugStack = sw.toString();

		Iterator<String> lines = Stream.of(debugStack.split("\n"))
				.map(String::trim)
				.iterator();

		while (lines.hasNext()) {
			String line = lines.next();
			if (line.endsWith("Error has been observed at the following site(s):")) {
				break;
			}
		}

		assertThat(lines.next())
				.as("first traceback line")
				.endsWith("*__Mono.map ⇢ at reactor.tools.agent.ReactorDebugAgentTest.stackTrace(ReactorDebugAgentTest.java:" + (baseline + 2) + ")");

		assertThat(lines.next())
				.as("second traceback line")
				.endsWith("|_          ⇢ at reactor.tools.agent.ReactorDebugAgentTest.methodReturningMono(ReactorDebugAgentTest.java:" + (methodReturningMonoBaseline + 2) + ")");
	}

	@Test
	public void cglibProxies() {
		ProxyMe proxy = (ProxyMe) Enhancer.create(ProxyMe.class, NoOp.INSTANCE);

		assertThat(proxy.doSomething()).isInstanceOf(ProxyMe.MyMono.class);
	}

	static final int methodReturningMonoBaseline = getBaseline();
	private Mono<Integer> methodReturningMono(Mono<Integer> mono) {
		return mono;
	}

	private Mono<Integer> methodReturningNullMono() {
		return null;
	}

	private static int getBaseline() {
		return new Exception().getStackTrace()[1].getLineNumber();
	}

	static class ProxyMe {
		static class MyMono extends Mono<Void> {
			@Override
			public void subscribe(CoreSubscriber<? super Void> actual) {
				Mono.<Void>empty().subscribe(actual);
			}
		}

		Mono<Void> doSomething() {
			Mono<Void> myMono = new MyMono();
			// Make it think that there were operator calls inside
			myMono.then();
			return myMono;
		}
	}
}