Easy part of CompileStatic migration

If groovy compiles without CompileStatic - code will be compiled in dynamic way,
e.g. All type checks will be in runtime. Erased types in bytecode.
With CompileStatic - compiler will save all typed in bytecode.
If all types saved, we can do static analysis of bytecode with java 8 capability.
More details can be found here: google#565 (comment)

Author: rougsig

build.gradle

@@ -61,6 +61,7 @@ dependencies {
   implementation 'commons-lang:commons-lang:2.6'
 
   testImplementation 'junit:junit:4.12'
+  testImplementation "com.android.tools.build:gradle:3.5.0"
   testImplementation('org.spockframework:spock-core:1.0-groovy-2.4') {
     exclude module: 'groovy-all'
   }

src/main/groovy/com/google/protobuf/gradle/ArchiveActionFacade.java

@@ -28,18 +28,21 @@
  */
 package com.google.protobuf.gradle;
 
+import groovy.transform.CompileStatic;
 import org.gradle.api.Project;
 import org.gradle.api.file.FileTree;
 import org.gradle.api.internal.file.FileOperations;
 
 import javax.inject.Inject;
 
+@CompileStatic
 public interface ArchiveActionFacade {
 
     FileTree zipTree(Object path);
 
     FileTree tarTree(Object path);
 
+    @CompileStatic
     class ProjectBased implements ArchiveActionFacade {
 
         private final Project project;
@@ -59,6 +62,7 @@ public FileTree tarTree(Object path) {
         }
     }
 
+    @CompileStatic
     abstract class ServiceBased implements ArchiveActionFacade {
 
         // TODO Use public ArchiveOperations from Gradle 6.6 instead

src/main/groovy/com/google/protobuf/gradle/CopyActionFacade.java

@@ -29,6 +29,7 @@
  */
 package com.google.protobuf.gradle;
 
+import groovy.transform.CompileStatic;
 import org.gradle.api.Action;
 import org.gradle.api.Project;
 import org.gradle.api.file.CopySpec;
@@ -42,9 +43,11 @@
  * {@link org.gradle.api.file.FileSystemOperations} if available (Gradle 6.0+) or {@link org.gradle.api.Project#copy} if
  * the version of Gradle is below 6.0.
  */
+@CompileStatic
 interface CopyActionFacade {
     WorkResult copy(Action<? super CopySpec> var1);
 
+    @CompileStatic
     class ProjectBased implements CopyActionFacade {
         private final Project project;
 
@@ -58,6 +61,7 @@ public WorkResult copy(Action<? super CopySpec> action) {
         }
     }
 
+    @CompileStatic
     abstract class FileSystemOperationsBased implements CopyActionFacade {
         @Inject
         public abstract FileSystemOperations getFileSystemOperations();

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

@@ -28,7 +28,8 @@
  */
 package com.google.protobuf.gradle
 
-import groovy.transform.CompileDynamic
+
+import groovy.transform.CompileStatic
 import org.gradle.api.Named
 
 /**
@@ -37,7 +38,7 @@ import org.gradle.api.Named
  * configured, the plugin should try to run the executable from system search
  * path.
  */
-@CompileDynamic
+@CompileStatic
 class ExecutableLocator implements Named {
 
   private final String name

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

@@ -29,8 +29,6 @@
  */
 package com.google.protobuf.gradle
 
-import static java.nio.charset.StandardCharsets.US_ASCII
-
 import com.google.common.base.Preconditions
 import com.google.common.collect.ImmutableList
 import groovy.transform.CompileDynamic
@@ -49,25 +47,14 @@ import org.gradle.api.provider.MapProperty
 import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.provider.ProviderFactory
-import org.gradle.api.tasks.CacheableTask
-import org.gradle.api.tasks.IgnoreEmptyDirectories
-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.OutputFile
-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.api.tasks.*
 import org.gradle.util.ConfigureUtil
 
 import javax.annotation.Nullable
 import javax.inject.Inject
 
+import static java.nio.charset.StandardCharsets.US_ASCII
+
 /**
  * The task that compiles proto files into Java files.
  */

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

@@ -29,15 +29,16 @@
  */
 package com.google.protobuf.gradle
 
-import groovy.transform.CompileDynamic
+
+import groovy.transform.CompileStatic
 import org.gradle.api.Project
 import org.gradle.api.internal.file.FileResolver
 import org.gradle.util.ConfigureUtil
 
 /**
  * Adds the protobuf {} block as a property of the project.
  */
-@CompileDynamic
+@CompileStatic
 class ProtobufConvention {
     ProtobufConvention(Project project, FileResolver fileResolver) {
         protobuf = new ProtobufConfigurator(project, fileResolver)

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

@@ -28,7 +28,8 @@
  */
 package com.google.protobuf.gradle
 
-import groovy.transform.CompileDynamic
+import com.google.gradle.osdetector.OsDetector
+import groovy.transform.CompileStatic
 import org.gradle.api.NamedDomainObjectContainer
 import org.gradle.api.Project
 import org.gradle.api.artifacts.Configuration
@@ -38,12 +39,12 @@ import org.gradle.api.file.FileCollection
 /**
  * Holds locations of all external executables, i.e., protoc and plugins.
  */
-@CompileDynamic
+@CompileStatic
 class ToolsLocator {
 
   private final Project project
-  private final ExecutableLocator protoc
-  private final NamedDomainObjectContainer<ExecutableLocator> plugins
+  final ExecutableLocator protoc
+  final NamedDomainObjectContainer<ExecutableLocator> plugins
 
   static List<String> artifactParts(String artifactCoordinate) {
     String artifact
@@ -53,11 +54,13 @@ class ToolsLocator {
     String version
     String classifier
 
-    (artifact, extension) = artifactCoordinate.tokenize('@')
+    def artifactCoordinateTokenized = artifactCoordinate.tokenize('@')
+    (artifact, extension) = [artifactCoordinateTokenized[0], artifactCoordinateTokenized[1]]
     if (extension == null && artifactCoordinate.endsWith('@')) {
       extension = ''
     }
-    (group, name, version, classifier) = artifact.tokenize(':')
+    def artifactTokenized = artifact.tokenize(':')
+    (group, name, version, classifier) = [artifactTokenized[0], artifactTokenized[1], artifactTokenized[2], artifactTokenized[3]]
 
     return [group, name, version, classifier, extension]
   }
@@ -92,19 +95,20 @@ class ToolsLocator {
 
   void registerDependencyWithTasks(ExecutableLocator locator, Collection<GenerateProtoTask> protoTasks) {
     // create a project configuration dependency for the artifact
-    Configuration config = project.configurations.create("protobufToolsLocator_${locator.name}") {
-      visible = false
-      transitive = false
-      extendsFrom = []
+    Configuration config = project.configurations.create("protobufToolsLocator_${locator.name}") { Configuration conf ->
+      conf.visible = false
+      conf.transitive = false
     }
     String groupId, artifact, version, classifier, extension
-    (groupId, artifact, version, classifier, extension) = artifactParts(locator.artifact)
+    def osdetector = project.extensions.getByName("osdetector") as OsDetector
+    def parts = artifactParts(locator.artifact)
+    (groupId, artifact, version, classifier, extension) = [parts[0], parts[1], parts[2], parts[3], parts[4]]
     Map<String, String> notation = [
-            group:groupId,
-            name:artifact,
-            version:version,
-            classifier:classifier ?: project.osdetector.classifier,
-            ext:extension ?: 'exe',
+      group     : groupId,
+      name      : artifact,
+      version   : version,
+      classifier: classifier ?: osdetector.classifier,
+      ext       : extension ?: 'exe',
     ]
     Dependency dep = project.dependencies.add(config.name, notation)
     FileCollection artifactFiles = config.fileCollection(dep)

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

@@ -29,7 +29,7 @@
 package com.google.protobuf.gradle
 
 import com.google.common.base.Preconditions
-import groovy.transform.CompileDynamic
+import groovy.transform.CompileStatic
 import org.apache.commons.lang.StringUtils
 import org.gradle.api.GradleException
 import org.gradle.api.Project
@@ -43,7 +43,7 @@ import java.util.regex.Matcher
 /**
  * Utility classes.
  */
-@CompileDynamic
+@CompileStatic
 class Utils {
   /**
    * Returns the conventional name of a configuration for a sourceSet