Fix input and output annotations (#364)

With Gradle 6.0 we are starting to enforce annotations on all task getters. Non ad-hoc tasks should use annotations in place of the `Task.getInputs()` and `getOutputs()` APIs. Due to these changes with Gradle 6.0 the applying the Protobuf plugin results in the following deprecation warnings being displayed:

```text
   > Warning: Type 'GenerateProtoTask': property 'buildType' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'builtins' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'descriptorPath' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'descriptorSetOptions' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'fileResolver' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'flavors' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'generateDescriptorSet' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'isTest' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'isTestVariant' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'outputSourceDirectorySet' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'plugins' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'sourceFiles' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'sourceSet' is not annotated with an input or output annotation.
   > Warning: Type 'GenerateProtoTask': property 'variant' is not annotated with an input or output annotation.
   > Warning: Type 'ProtobufExtract': property 'destDir' is not annotated with an input or output annotation.
   > Warning: Type 'ProtobufExtract': property 'isTest' is not annotated with an input or output annotation.
```

This PR fixes the problems and the warnings are removed. This is based on #351 by @lptr

build.gradle

@@ -14,6 +14,7 @@ apply plugin: 'groovy'
 apply plugin: 'kotlin'
 apply plugin: 'maven'
 apply plugin: 'signing'
+apply plugin: 'java-gradle-plugin'
 apply plugin: 'com.jfrog.bintray'
 apply plugin: 'com.gradle.plugin-publish'
 apply plugin: 'com.github.ben-manes.versions'

src/main/groovy/com/google/protobuf/gradle/GenerateProtoTask.groovy

@@ -42,15 +42,27 @@ import org.gradle.api.internal.file.DefaultSourceDirectorySet
 import org.gradle.api.internal.file.FileResolver
 import org.gradle.api.internal.file.collections.DefaultDirectoryFileTreeFactory
 import org.gradle.api.logging.LogLevel
+import org.gradle.api.tasks.CacheableTask
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.Internal
+import org.gradle.api.tasks.Nested
+import org.gradle.api.tasks.Optional
+import org.gradle.api.tasks.OutputDirectory
+import org.gradle.api.tasks.PathSensitive
 import org.gradle.api.tasks.PathSensitivity
+import org.gradle.api.tasks.SkipWhenEmpty
 import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.TaskAction
 import org.gradle.util.ConfigureUtil
 
+import javax.annotation.Nullable
+
 /**
  * The task that compiles proto files into Java files.
  */
 // TODO(zhangkun83): add per-plugin output dir reconfiguraiton.
+@CacheableTask
 public class GenerateProtoTask extends DefaultTask {
   // Windows CreateProcess has command line limit of 32768:
   // https://msdn.microsoft.com/en-us/library/windows/desktop/ms682425(v=vs.85).aspx
@@ -86,6 +98,7 @@ public class GenerateProtoTask extends DefaultTask {
    *
    * Default: false
    */
+  @Internal("Handled as input via getDescriptorSetOptionsForCaching()")
   boolean generateDescriptorSet
 
   /**
@@ -98,23 +111,29 @@ public class GenerateProtoTask extends DefaultTask {
      *
      * Default: null
      */
+    @Nullable
+    @Optional
+    @Input
     GString path
 
     /**
      * If true, source information (comments, locations) will be included in the descriptor set.
      *
      * Default: false
      */
+    @Input
     boolean includeSourceInfo
 
     /**
      * If true, imports are included in the descriptor set, such that it is self-containing.
      *
      * Default: false
      */
+    @Input
     boolean includeImports
   }
 
+  @Internal("Handled as input via getDescriptorSetOptionsForCaching()")
   final DescriptorSetOptions descriptorSetOptions = new DescriptorSetOptions()
 
   // protoc allows you to prefix comma-delimited options to the path in
@@ -177,7 +196,11 @@ public class GenerateProtoTask extends DefaultTask {
     checkInitializing()
     Preconditions.checkState(this.outputBaseDir == null, 'outputBaseDir is already set')
     this.outputBaseDir = outputBaseDir
-    outputs.dir outputBaseDir
+  }
+
+  @OutputDirectory
+  String getOutputBaseDir() {
+    return outputBaseDir
   }
 
   void setSourceSet(SourceSet sourceSet) {
@@ -214,38 +237,52 @@ public class GenerateProtoTask extends DefaultTask {
     this.fileResolver = fileResolver
   }
 
+  @Internal("Inputs tracked in getSourceFiles()")
   SourceSet getSourceSet() {
     Preconditions.checkState(!Utils.isAndroidProject(project),
         'sourceSet should not be used in an Android project')
     Preconditions.checkNotNull(sourceSet, 'sourceSet is not set')
     return sourceSet
   }
 
+  @SkipWhenEmpty
+  @InputFiles
+  @PathSensitive(PathSensitivity.RELATIVE)
   FileCollection getSourceFiles() {
     return sourceFiles
   }
 
+  @InputFiles
+  @PathSensitive(PathSensitivity.RELATIVE)
+  FileCollection getIncludeDirs() {
+    return includeDirs
+  }
+
+  @Internal("Not an actual input to the task, only used to find tasks belonging to a variant")
   Object getVariant() {
     Preconditions.checkState(Utils.isAndroidProject(project),
         'variant should not be used in a Java project')
     Preconditions.checkNotNull(variant, 'variant is not set')
     return variant
   }
 
+  @Internal("Not an actual input to the task, only used to find tasks belonging to a variant")
   boolean getIsTestVariant() {
     Preconditions.checkState(Utils.isAndroidProject(project),
         'isTestVariant should not be used in a Java project')
     Preconditions.checkNotNull(variant, 'variant is not set')
     return isTestVariant
   }
 
+  @Internal("Not an actual input to the task, only used to find tasks belonging to a variant")
   ImmutableList<String> getFlavors() {
     Preconditions.checkState(Utils.isAndroidProject(project),
         'flavors should not be used in a Java project')
     Preconditions.checkNotNull(flavors, 'flavors is not set')
     return flavors
   }
 
+  @Internal("Not an actual input to the task, only used to find tasks belonging to a variant")
   String getBuildType() {
     Preconditions.checkState(Utils.isAndroidProject(project),
         'buildType should not be used in a Java project')
@@ -255,11 +292,6 @@ public class GenerateProtoTask extends DefaultTask {
     return buildType
   }
 
-  FileResolver getFileResolver() {
-    Preconditions.checkNotNull(fileResolver)
-    return fileResolver
-  }
-
   void doneInitializing() {
     Preconditions.checkState(state == State.INIT, "Invalid state: ${state}")
     state = State.CONFIG
@@ -270,6 +302,7 @@ public class GenerateProtoTask extends DefaultTask {
     state = State.FINALIZED
   }
 
+  @Internal("Tracked as an input via getDescriptorSetOptionsForCaching()")
   String getDescriptorPath() {
     if (!generateDescriptorSet) {
       throw new IllegalStateException(
@@ -299,6 +332,7 @@ public class GenerateProtoTask extends DefaultTask {
   /**
    * Returns the container of protoc builtins.
    */
+  @Internal("Tracked as an input via getBuiltinsForCaching()")
   public NamedDomainObjectContainer<PluginOptions> getBuiltins() {
     checkCanConfig()
     return builtins
@@ -316,6 +350,7 @@ public class GenerateProtoTask extends DefaultTask {
   /**
    * Returns the container of protoc plugins.
    */
+  @Internal("Tracked as an input via getPluginsForCaching()")
   public NamedDomainObjectContainer<PluginOptions> getPlugins() {
     checkCanConfig()
     return plugins
@@ -334,9 +369,6 @@ public class GenerateProtoTask extends DefaultTask {
   public void addIncludeDir(FileCollection dir) {
     checkCanConfig()
     includeDirs.from(dir)
-    // Register all files under the directory as input so that Gradle will check their changes for
-    // incremental build
-    inputs.files(dir).withPathSensitivity(PathSensitivity.RELATIVE)
   }
 
   /**
@@ -345,13 +377,12 @@ public class GenerateProtoTask extends DefaultTask {
   public void addSourceFiles(FileCollection files) {
     checkCanConfig()
     sourceFiles.from(files)
-    // Register the files as input so that Gradle will check their changes for incremental build
-    inputs.files(files).withPathSensitivity(PathSensitivity.RELATIVE)
   }
 
   /**
    * Returns true if the Java source set or Android variant is test related.
    */
+  @Input
   public boolean getIsTest() {
     if (Utils.isAndroidProject(project)) {
       return isTestVariant
@@ -379,13 +410,15 @@ public class GenerateProtoTask extends DefaultTask {
       return this
     }
 
+    @Input
     public List<String> getOptions() {
       return options
     }
 
     /**
      * Returns the name of the plugin or builtin.
      */
+    @Input
     @Override
     public String getName() {
       return name
@@ -401,6 +434,7 @@ public class GenerateProtoTask extends DefaultTask {
     /**
      * Returns the relative outputDir for this plugin.  If outputDir is not specified, name is used.
      */
+    @Input
     public String getOutputSubDir() {
       if (outputSubDir != null) {
         return outputSubDir
@@ -421,6 +455,7 @@ public class GenerateProtoTask extends DefaultTask {
    * Returns a {@code SourceDirectorySet} representing the generated source
    * directories.
    */
+  @Internal
   SourceDirectorySet getOutputSourceDirectorySet() {
     String srcSetName = "generate-proto-" + name
     SourceDirectorySet srcSet
@@ -504,6 +539,31 @@ public class GenerateProtoTask extends DefaultTask {
     }
   }
 
+  /**
+   * Used to expose inputs to Gradle, not to be called directly.
+   */
+  @Optional
+  @Nested
+  protected DescriptorSetOptions getDescriptorSetOptionsForCaching() {
+    return generateDescriptorSet ? descriptorSetOptions : null
+  }
+
+  /**
+   * Used to expose inputs to Gradle, not to be called directly.
+   */
+  @Nested
+  protected Collection<PluginOptions> getBuiltinsForCaching() {
+    return builtins
+  }
+
+  /**
+   * Used to expose inputs to Gradle, not to be called directly.
+   */
+  @Nested
+  protected Collection<PluginOptions> getPluginsForCaching() {
+    return plugins
+  }
+
   private static enum State {
     INIT, CONFIG, FINALIZED
   }

src/main/groovy/com/google/protobuf/gradle/ProtobufExtract.groovy

@@ -31,6 +31,12 @@ package com.google.protobuf.gradle
 
 import com.google.common.base.Preconditions
 import org.gradle.api.DefaultTask
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.OutputDirectory
+import org.gradle.api.tasks.PathSensitive
+import org.gradle.api.tasks.PathSensitivity
 import org.gradle.api.tasks.TaskAction
 
 /**
@@ -43,21 +49,30 @@ class ProtobufExtract extends DefaultTask {
    */
   private File destDir
   private Boolean isTest = null
+  private final ConfigurableFileCollection inputFiles = project.files()
 
   public void setIsTest(boolean isTest) {
     this.isTest = isTest
   }
 
+  @Input
   public boolean getIsTest() {
     Preconditions.checkNotNull(isTest)
     return isTest
   }
 
+  @InputFiles
+  // TODO Review if NAME_ONLY is the best path sensitivity to use here
+  @PathSensitive(PathSensitivity.NAME_ONLY)
+  public ConfigurableFileCollection getInputFiles() {
+    return inputFiles
+  }
+
   @TaskAction
   void extract() {
     destDir.mkdir()
     boolean warningLogged = false
-    inputs.files.each { file ->
+    inputFiles.each { file ->
       logger.debug "Extracting protos from ${file} to ${destDir}"
       if (file.isDirectory()) {
         project.copy {
@@ -113,6 +128,7 @@ class ProtobufExtract extends DefaultTask {
     outputs.dir destDir
   }
 
+  @OutputDirectory
   protected File getDestDir() {
     return destDir
   }

src/main/groovy/com/google/protobuf/gradle/ProtobufPlugin.groovy

@@ -43,7 +43,6 @@ import org.gradle.api.internal.file.FileResolver
 import org.gradle.api.internal.file.collections.DefaultDirectoryFileTreeFactory
 import org.gradle.api.logging.LogLevel
 import org.gradle.api.plugins.AppliedPlugin
-import org.gradle.api.tasks.PathSensitivity
 import org.gradle.api.tasks.SourceSet
 
 import javax.inject.Inject
@@ -336,8 +335,7 @@ class ProtobufPlugin implements Plugin<Project> {
         task = project.tasks.create(extractProtosTaskName, ProtobufExtract) {
           description = "Extracts proto files/dependencies specified by 'protobuf' configuration"
           destDir = getExtractedProtosDir(sourceSetName) as File
-          inputs.files(project.configurations[Utils.getConfigName(sourceSetName, 'protobuf')])
-                  .withPathSensitivity(PathSensitivity.NAME_ONLY)
+          inputFiles.from(project.configurations[Utils.getConfigName(sourceSetName, 'protobuf')])
           isTest = Utils.isTest(sourceSetName)
         }
       }
@@ -365,9 +363,8 @@ class ProtobufPlugin implements Plugin<Project> {
         task = project.tasks.create(extractIncludeProtosTaskName, ProtobufExtract) {
           description = "Extracts proto files from compile dependencies for includes"
           destDir = getExtractedIncludeProtosDir(sourceSetOrVariantName) as File
-          inputs.files (compileClasspathConfiguration
+          inputFiles.from(compileClasspathConfiguration
             ?: project.configurations[Utils.getConfigName(sourceSetOrVariantName, 'compile')])
-                  .withPathSensitivity(PathSensitivity.NAME_ONLY)
 
           // TL; DR: Make protos in 'test' sourceSet able to import protos from the 'main'
           // sourceSet.  Sub-configurations, e.g., 'testCompile' that extends 'compile', don't
@@ -380,16 +377,15 @@ class ProtobufPlugin implements Plugin<Project> {
             // ad-hoc solution that manually includes the source protos of 'main' and its
             // dependencies.
             if (Utils.isTest(sourceSetOrVariantName)) {
-              inputs.files getSourceSets()['main'].proto
-              inputs.files testedCompileClasspathConfiguration ?: project.configurations['compile']
+              inputFiles.from getSourceSets()['main'].proto
+              inputFiles.from testedCompileClasspathConfiguration ?: project.configurations['compile']
             }
           } else {
             // In Java projects, the compileClasspath of the 'test' sourceSet includes all the
             // 'resources' of the output of 'main', in which the source protos are placed.  This is
             // nicer than the ad-hoc solution that Android has, because it works for any extended
             // configuration, not just 'testCompile'.
-            inputs.files (getSourceSets()[sourceSetOrVariantName].compileClasspath)
-                    .withPathSensitivity(PathSensitivity.NAME_ONLY)
+            inputFiles.from getSourceSets()[sourceSetOrVariantName].compileClasspath
           }
           isTest = Utils.isTest(sourceSetOrVariantName)
         }

src/main/groovy/com/google/protobuf/gradle/ToolsLocator.groovy

@@ -33,6 +33,7 @@ import org.gradle.api.NamedDomainObjectContainer
 import org.gradle.api.Project
 import org.gradle.api.artifacts.Configuration
 import org.gradle.api.artifacts.Dependency
+import org.gradle.api.tasks.PathSensitivity
 
 /**
  * Holds locations of all external executables, i.e., protoc and plugins.
@@ -110,6 +111,8 @@ class ToolsLocator {
       if (protoc.is(locator) || protoTask.hasPlugin(locator.name)) {
         // register the configuration dependency as a task input
         protoTask.inputs.files(config)
+            .withPathSensitivity(PathSensitivity.NONE)
+            .withPropertyName("config.${locator.name}")
 
         protoTask.doFirst {
           if (locator.path == null) {