Update BuildInfo to support Gradle's configuration cache

See gh-22922

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/buildinfo/BuildInfo.java

@@ -24,6 +24,7 @@ import java.util.Map;
 import org.gradle.api.Action;
 import org.gradle.api.Project;
 import org.gradle.api.Task;
+import org.gradle.api.file.DirectoryProperty;
 import org.gradle.api.internal.ConventionTask;
 import org.gradle.api.tasks.Nested;
 import org.gradle.api.tasks.OutputDirectory;
@@ -44,7 +45,12 @@ public class BuildInfo extends ConventionTask {
 
 	private final BuildInfoProperties properties = new BuildInfoProperties(getProject());
 
-	private File destinationDir;
+	private final DirectoryProperty destinationDir;
+
+	public BuildInfo() {
+		this.destinationDir = getProject().getObjects().directoryProperty()
+				.convention(getProject().getLayout().getBuildDirectory());
+	}
 
 	/**
 	 * Generates the {@code build-info.properties} file in the configured
@@ -73,7 +79,7 @@ public class BuildInfo extends ConventionTask {
 	 */
 	@OutputDirectory
 	public File getDestinationDir() {
-		return (this.destinationDir != null) ? this.destinationDir : getProject().getBuildDir();
+		return this.destinationDir.getAsFile().get();
 	}
 
 	/**
@@ -81,7 +87,7 @@ public class BuildInfo extends ConventionTask {
 	 * @param destinationDir the destination directory
 	 */
 	public void setDestinationDir(File destinationDir) {
-		this.destinationDir = destinationDir;
+		this.destinationDir.set(destinationDir);
 	}
 
 	/**

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/buildinfo/BuildInfoProperties.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.gradle.tasks.buildinfo;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
 import java.io.Serializable;
 import java.time.Instant;
 import java.util.HashMap;
@@ -23,6 +25,7 @@ import java.util.Map;
 
 import org.gradle.api.Project;
 import org.gradle.api.provider.Property;
+import org.gradle.api.provider.Provider;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Optional;
 
@@ -35,6 +38,8 @@ import org.gradle.api.tasks.Optional;
 @SuppressWarnings("serial")
 public class BuildInfoProperties implements Serializable {
 
+	private transient Instant creationTime = Instant.now();
+
 	private final Property<String> group;
 
 	private final Property<String> artifact;
@@ -43,22 +48,35 @@ public class BuildInfoProperties implements Serializable {
 
 	private final Property<String> name;
 
-	private final Property<Instant> time;
+	private final Property<Long> time;
+
+	private boolean timeConfigured = false;
 
 	private Map<String, Object> additionalProperties = new HashMap<>();
 
 	BuildInfoProperties(Project project) {
-		this.time = project.getObjects().property(Instant.class);
-		this.time.set(Instant.now());
+		this.time = project.getObjects().property(Long.class);
 		this.group = project.getObjects().property(String.class);
 		this.group.set(project.provider(() -> project.getGroup().toString()));
 		this.artifact = project.getObjects().property(String.class);
 		this.version = project.getObjects().property(String.class);
-		this.version.set(project.provider(() -> project.getVersion().toString()));
+		this.version.set(projectVersion(project));
 		this.name = project.getObjects().property(String.class);
 		this.name.set(project.provider(project::getName));
 	}
 
+	private Provider<String> projectVersion(Project project) {
+		try {
+			Provider<String> externalVersionProperty = project.getProviders().gradleProperty("version")
+					.forUseAtConfigurationTime();
+			externalVersionProperty.getOrNull();
+		}
+		catch (NoSuchMethodError ex) {
+			// Gradle < 6.5
+		}
+		return project.provider(() -> project.getVersion().toString());
+	}
+
 	/**
 	 * Returns the value used for the {@code build.group} property. Defaults to the
 	 * {@link Project#getGroup() Project's group}.
@@ -142,7 +160,14 @@ public class BuildInfoProperties implements Serializable {
 	@Input
 	@Optional
 	public Instant getTime() {
-		return this.time.getOrNull();
+		Long epochMillis = this.time.getOrNull();
+		if (epochMillis != null) {
+			return Instant.ofEpochMilli(epochMillis);
+		}
+		if (this.timeConfigured) {
+			return null;
+		}
+		return this.creationTime;
 	}
 
 	/**
@@ -150,7 +175,8 @@ public class BuildInfoProperties implements Serializable {
 	 * @param time the build time
 	 */
 	public void setTime(Instant time) {
-		this.time.set(time);
+		this.timeConfigured = true;
+		this.time.set((time != null) ? time.toEpochMilli() : null);
 	}
 
 	/**
@@ -173,4 +199,9 @@ public class BuildInfoProperties implements Serializable {
 		this.additionalProperties = additionalProperties;
 	}
 
+	private void readObject(ObjectInputStream input) throws ClassNotFoundException, IOException {
+		input.defaultReadObject();
+		this.creationTime = Instant.now();
+	}
+
 }