Enforce Checkstyle failures

* Fix `FileSupplierConfiguration` to use `toReactivePublisher(true)`
to defer a start of channel adapters until reactive subscription.
* Also use `IntegrationReactiveUtils.messageSourceToFlux()` API instead of manual Reactor API composition

build.gradle

@@ -114,7 +114,6 @@ configure(javaProjects) { subproject ->
 	checkstyle {
 		toolVersion = '10.3'
 		configDirectory = rootProject.file('etc/checkstyle')
-		ignoreFailures = true
 	}
 
 	// dependencies that are common across all java projects

supplier/spring-file-supplier/src/main/java/org/springframework/cloud/fn/supplier/file/FileSupplierConfiguration.java

@@ -21,12 +21,9 @@
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
-import reactor.core.publisher.Mono;
-import reactor.core.scheduler.Schedulers;
+import reactor.util.context.Context;
 
 import org.springframework.beans.factory.BeanInitializationException;
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
@@ -35,7 +32,6 @@
 import org.springframework.cloud.fn.common.file.FileReadingMode;
 import org.springframework.cloud.fn.common.file.FileUtils;
 import org.springframework.context.annotation.Bean;
-import org.springframework.context.annotation.Lazy;
 import org.springframework.integration.dsl.IntegrationFlow;
 import org.springframework.integration.dsl.IntegrationFlowBuilder;
 import org.springframework.integration.file.FileReadingMessageSource;
@@ -47,6 +43,7 @@
 import org.springframework.integration.file.filters.RegexPatternFileListFilter;
 import org.springframework.integration.file.filters.SimplePatternFileListFilter;
 import org.springframework.integration.metadata.ConcurrentMetadataStore;
+import org.springframework.integration.util.IntegrationReactiveUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.util.StringUtils;
@@ -67,11 +64,6 @@ public class FileSupplierConfiguration {
 
 	private final FileConsumerProperties fileConsumerProperties;
 
-	@Autowired
-	@Lazy
-	@Qualifier("fileMessageSource")
-	private FileReadingMessageSource fileMessageSource;
-
 	public FileSupplierConfiguration(FileSupplierProperties fileSupplierProperties,
 			FileConsumerProperties fileConsumerProperties) {
 
@@ -110,21 +102,18 @@ public FileInboundChannelAdapterSpec fileMessageSource(FileListFilter<File> file
 	}
 
 	@Bean
-	public Flux<Message<?>> fileMessageFlux() {
-		return Mono
-			.<Message<?>>create(
-					(monoSink) -> monoSink.onRequest((value) -> monoSink.success(this.fileMessageSource.receive())))
-			.subscribeOn(Schedulers.boundedElastic())
-			.repeatWhenEmpty((it) -> it.delayElements(this.fileSupplierProperties.getDelayWhenEmpty()))
-			.repeat()
-			.doOnRequest((r) -> this.fileMessageSource.start());
+	public Flux<Message<File>> fileMessageFlux(FileReadingMessageSource fileReadingMessageSource) {
+		return IntegrationReactiveUtils.messageSourceToFlux(fileReadingMessageSource)
+			.contextWrite(Context.of(IntegrationReactiveUtils.DELAY_WHEN_EMPTY_KEY,
+					this.fileSupplierProperties.getDelayWhenEmpty()))
+			.doOnRequest((r) -> fileReadingMessageSource.start());
 	}
 
 	@Bean
 	@ConditionalOnExpression("environment['file.consumer.mode'] != 'ref'")
 	public Publisher<Message<Object>> fileReadingFlow(Flux<Message<?>> fileMessageFlux) {
 		IntegrationFlowBuilder flowBuilder = IntegrationFlow.from(fileMessageFlux);
-		return FileUtils.enhanceFlowForReadingMode(flowBuilder, this.fileConsumerProperties).toReactivePublisher();
+		return FileUtils.enhanceFlowForReadingMode(flowBuilder, this.fileConsumerProperties).toReactivePublisher(true);
 	}
 
 	@Bean