Use spring-pdf backend for PDF generation

Update `asciidoctorPdf` tasks to use the `spring-pdf` backend so that
chomped elements and @fold:on/@fold:off comments are hidden.

Closes gh-26373

buildSrc/build.gradle

@@ -18,8 +18,7 @@ dependencies {
 	implementation("com.fasterxml.jackson.core:jackson-databind:2.11.4")
 	implementation("commons-codec:commons-codec:1.13")
 	implementation("org.apache.maven:maven-embedder:3.6.2")
-	implementation("org.asciidoctor:asciidoctor-gradle-jvm:3.1.0")
-	implementation("org.asciidoctor:asciidoctor-gradle-jvm-pdf:3.1.0")
+	implementation("org.asciidoctor:asciidoctor-gradle-jvm:3.3.2")
 	implementation("org.gradle:test-retry-gradle-plugin:1.1.9")
 	implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.0-RC")
 	implementation("org.jetbrains.kotlin:kotlin-compiler-embeddable:1.5.0-RC")

buildSrc/src/main/java/org/springframework/boot/build/AsciidoctorConventions.java

@@ -98,6 +98,8 @@ class AsciidoctorConventions {
 		Configuration asciidoctorExtensions = configurations.maybeCreate(EXTENSIONS_CONFIGURATION);
 		asciidoctorExtensions.getDependencies().add(project.getDependencies()
 				.create("io.spring.asciidoctor.backends:spring-asciidoctor-backends:0.0.1-SNAPSHOT"));
+		asciidoctorExtensions.getDependencies()
+				.add(project.getDependencies().create("org.asciidoctor:asciidoctorj-pdf:1.5.3"));
 		Configuration dependencyManagement = configurations.findByName("dependencyManagement");
 		if (dependencyManagement != null) {
 			asciidoctorExtensions.extendsFrom(dependencyManagement);
@@ -111,7 +113,9 @@ class AsciidoctorConventions {
 		asciidoctorTask.baseDirFollowsSourceDir();
 		createSyncDocumentationSourceTask(project, asciidoctorTask);
 		if (asciidoctorTask instanceof AsciidoctorTask) {
-			configureAsciidoctorHtmlTask((AsciidoctorTask) asciidoctorTask);
+			boolean pdf = asciidoctorTask.getName().toLowerCase().contains("pdf");
+			String backend = (!pdf) ? "spring-html" : "spring-pdf";
+			((AsciidoctorTask) asciidoctorTask).outputOptions((outputOptions) -> outputOptions.backends(backend));
 		}
 	}
 
@@ -146,8 +150,4 @@ class AsciidoctorConventions {
 		return syncDocumentationSource;
 	}
 
-	private void configureAsciidoctorHtmlTask(AsciidoctorTask asciidoctorTask) {
-		asciidoctorTask.outputOptions((outputOptions) -> outputOptions.backends("spring-html"));
-	}
-
 }

spring-boot-project/spring-boot-actuator-autoconfigure/build.gradle

 plugins {
     id "java-library"
 	id "org.asciidoctor.jvm.convert"
-	id "org.asciidoctor.jvm.pdf"
 	id "org.springframework.boot.auto-configuration"
 	id "org.springframework.boot.conventions"
 	id "org.springframework.boot.deployed"
@@ -175,7 +174,7 @@ asciidoctor {
 	}
 }
 
-asciidoctorPdf {
+task asciidoctorPdf(type: org.asciidoctor.gradle.jvm.AsciidoctorTask) {
 	sources {
 		include "index.adoc"
 	}

spring-boot-project/spring-boot-docs/build.gradle

@@ -2,7 +2,6 @@ plugins {
 	id "java"
 	id "groovy"
 	id "org.asciidoctor.jvm.convert"
-	id "org.asciidoctor.jvm.pdf"
 	id "org.springframework.boot.conventions"
 	id "org.springframework.boot.deployed"
 }
@@ -257,7 +256,7 @@ asciidoctor {
 	}
 }
 
-asciidoctorPdf {
+task asciidoctorPdf(type: org.asciidoctor.gradle.jvm.AsciidoctorTask) {
 	sources {
 		include "*.singleadoc"
 	}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/build.gradle

@@ -2,7 +2,6 @@ plugins {
 	id "java-gradle-plugin"
 	id "maven-publish"
 	id "org.asciidoctor.jvm.convert"
-	id "org.asciidoctor.jvm.pdf"
 	id "org.springframework.boot.conventions"
 	id "org.springframework.boot.maven-repository"
 	id "org.springframework.boot.optional-dependencies"
@@ -82,7 +81,7 @@ asciidoctor {
 	attributes "stylesheet": "css/style.css"
 }
 
-asciidoctorPdf {
+task asciidoctorPdf(type: org.asciidoctor.gradle.jvm.AsciidoctorTask) {
 	sources {
 		include "index.adoc"
 	}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/build.gradle

 plugins {
 	id "org.asciidoctor.jvm.convert"
-	id "org.asciidoctor.jvm.pdf"
 	id "org.springframework.boot.conventions"
 	id "org.springframework.boot.maven-plugin"
 	id "org.springframework.boot.optional-dependencies"
@@ -74,15 +73,15 @@ asciidoctor {
 	}
 }
 
-syncDocumentationSourceForAsciidoctorPdf {
-	from(documentPluginGoals) {
-		into "asciidoc/goals"
+task asciidoctorPdf(type: org.asciidoctor.gradle.jvm.AsciidoctorTask) {
+	sources {
+		include "index.adoc"
 	}
 }
 
-asciidoctorPdf {
-	sources {
-		include "index.adoc"
+syncDocumentationSourceForAsciidoctorPdf {
+	from(documentPluginGoals) {
+		into "asciidoc/goals"
 	}
 }