feat: add new configuration necessary to support auto-value (#136)

Normally we would want to include auto-value in java-shared-dependencies, however auto-value includes a compiler extension and requires build configuration. #### Dependencies This change adds a dependencyManagement section with contains auto-value-annotations to manage which version of auto-value-annotations is used by projects and included in the dependency tree. #### Profiles Two new profiles have been added with the necessary configuration to include auto-value in the annotationProcessorPath when compiling. Auto value does not support java7 across all its artifacts consistently and requires us to have build configuration for java7 and java8+ to deal with this fact. When we drop support for java7 the autovalue-java7 profile can be deleted, and the jdk based activation of autovalue-java8 can be removed. ##### Activation Activation of each of the profiles is accomplished using a combination of jdk version and file-exists rules. Not all modules underneath this shared config use auto-value and thus we don't want to modify the annotationProcessorPath for everything. This allows the use of auto-value to be opt-in per module. To use either autovalue-java* profile, create an empty file in the module root named `EnableAutoValue.txt`. When the maven config is loaded it will look for this file, and if present activate the respective profile based on which version of java is running. Related to: googleapis/java-shared-dependencies#37

Author: BenWhitehead

pom.xml

@@ -60,6 +60,7 @@
  <site.installationModule>${project.artifactId}</site.installationModule>
  <report.jxr.inherited>false</report.jxr.inherited>
  <skipITs>true</skipITs>
+ <auto-value-annotation.version>1.7.2</auto-value-annotation.version>
  </properties>
 
  <build>
@@ -486,6 +487,21 @@
  </plugins>
  </reporting>
 
+ <dependencyManagement>
+ <dependencies>
+ <!--
+ We would prefer this be defined in our shared-dependencies, however due to
+ auto value being part of the compiler annotation processor, we are defining
+ it here to reduce the locations for version management.
+ -->
+ <dependency>
+ <groupId>com.google.auto.value</groupId>
+ <artifactId>auto-value-annotations</artifactId>
+ <version>${auto-value-annotation.version}</version>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
  <profiles>
  <profile>
  <id>release</id>
@@ -712,5 +728,91 @@
  </plugins>
  </build>
  </profile>
+ <profile>
+ <id>autovalue-java7</id>
+ <activation>
+ <jdk>1.7</jdk>
+ <file>
+ <exists>${basedir}/EnableAutoValue.txt</exists>
+ </file>
+ </activation>
+ <properties>
+ <!--
+ We need to back pin to 1.4 because it is the last version of auto-value
+ that was compiled for java 1.7.
+ -->
+ <auto-value.version>1.4</auto-value.version>
+ </properties>
+ <build>
+ <plugins>
+ <plugin>
+ <artifactId>maven-compiler-plugin</artifactId>
+ <configuration>
+ <annotationProcessorPaths>
+ <path>
+ <groupId>com.google.auto.value</groupId>
+ <artifactId>auto-value</artifactId>
+ <version>${auto-value.version}</version>
+ </path>
+ <!--
+ There is currently no available version of auto-service-annotations
+ in maven central compiled for java 1.7, so we can't include it here.
+
+ If you're using IntelliJ please use a newer jdk and set the language
+ level to 1.7 for your dev work.
+ -->
+ </annotationProcessorPaths>
+ </configuration>
+ </plugin>
+ </plugins>
+ </build>
+ </profile>
+ <profile>
+ <id>autovalue-java8</id>
+ <activation>
+ <jdk>[1.8,)</jdk>
+ <file>
+ <exists>${basedir}/EnableAutoValue.txt</exists>
+ </file>
+ </activation>
+ <build>
+ <plugins>
+ <plugin>
+ <artifactId>maven-compiler-plugin</artifactId>
+ <configuration>
+ <annotationProcessorPaths>
+ <path>
+ <groupId>com.google.auto.value</groupId>
+ <artifactId>auto-value</artifactId>
+ <version>${auto-value-annotation.version}</version>
+ </path>
+ <!--
+ Manually pull in auto-service-annotations so that it is part of the
+ processor path because auto-value has it set to provided scope.
+
+ This dependency is needed due to the retention change in
+ https://github.com/google/auto/commit/628df548685b4fc0f2a9af856f97cc2a68da246b
+ where the RetentionPolicy changed from SOURCE to CLASS.
+
+ Due to the RetentionPolicy change to CLASS we must have the
+ annotations available on the processor path otherwise the following
+ error will be thrown. (This is a particular problem with the
+ annotation processor configuration in IntelliJ)
+
+ Error:java: java.lang.NoClassDefFoundError: com/google/auto/service/AutoService
+ com.google.auto.service.AutoService
+ -->
+ <path>
+ <groupId>com.google.auto.service</groupId>
+ <artifactId>auto-service-annotations</artifactId>
+ <version>1.0-rc7</version>
+ </path>
+ </annotationProcessorPaths>
+ </configuration>
+ </plugin>
+ </plugins>
+ </build>
+ </profile>
+
  </profiles>
 </project>