Swap to Gradle's Plugin DSL for much of build

Examples and android projects were left unchanged. They can be changed
later.

No plugin versions were changed, to make this as non-functional of a
change as possible. Upgrading Gradle to 5.6 was necessary for
pluginManagement in settings.gradle.

all/build.gradle

@@ -1,15 +1,9 @@
-apply plugin: 'com.github.kt3k.coveralls'
+plugins {
+    id "com.github.kt3k.coveralls"
+}
 
 description = "gRPC: All"
 
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath 'org.kt3k.gradle.plugin:coveralls-gradle-plugin:2.0.1' }
-}
-
 def subprojects = [
     project(':grpc-api'),
     project(':grpc-auth'),

alts/build.gradle

@@ -1,23 +1,13 @@
-buildscript {
-    repositories { jcenter() }
-    dependencies { classpath 'com.github.jengelman.gradle.plugins:shadow:2.0.4' }
+plugins {
+    id "com.github.johnrengelman.shadow"
+    id "com.google.protobuf"
 }
 
-apply plugin: 'com.github.johnrengelman.shadow'
-
 description = "gRPC: ALTS"
 
 sourceCompatibility = 1.7
 targetCompatibility = 1.7
 
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
-}
-
 dependencies {
     compile project(':grpc-auth'),
             project(':grpc-core'),

benchmarks/build.gradle

@@ -1,12 +1,8 @@
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
-}
+plugins {
+    id "application"
 
-apply plugin: 'application'
+    id "com.google.protobuf"
+}
 
 description = "grpc Benchmarks"
 

build.gradle

@@ -1,15 +1,9 @@
-buildscript {
-    repositories {
-        mavenLocal()
-        maven { url "https://plugins.gradle.org/m2/" }
-    }
-    dependencies {
-        classpath 'com.google.gradle:osdetector-gradle-plugin:1.4.0'
-        classpath 'ru.vyarus:gradle-animalsniffer-plugin:1.5.0'
-        classpath 'net.ltgt.gradle:gradle-errorprone-plugin:0.8.1'
-        classpath "me.champeau.gradle:jmh-gradle-plugin:0.4.5"
-        classpath 'me.champeau.gradle:japicmp-gradle-plugin:0.2.5'
-    }
+plugins {
+    id "com.google.osdetector" apply false
+    id "me.champeau.gradle.japicmp" apply false
+    id "me.champeau.gradle.jmh" apply false
+    id "net.ltgt.errorprone" apply false
+    id "ru.vyarus.animalsniffer" apply false
 }
 
 import net.ltgt.gradle.errorprone.CheckSeverity
@@ -115,7 +109,6 @@ subprojects {
 
         configureProtoCompilation = {
             String generatedSourcePath = "${projectDir}/src/generated"
-            project.apply plugin: 'com.google.protobuf'
             project.protobuf {
                 protoc {
                     if (project.hasProperty('protoc')) {
@@ -205,7 +198,6 @@ subprojects {
             protobuf: "com.google.protobuf:protobuf-java:${protobufVersion}",
             protobuf_lite: "com.google.protobuf:protobuf-lite:3.0.1",
             protoc_lite: "com.google.protobuf:protoc-gen-javalite:3.0.0",
-            protobuf_plugin: 'com.google.protobuf:protobuf-gradle-plugin:0.8.8',
             protobuf_util: "com.google.protobuf:protobuf-java-util:${protobufVersion}",
             lang: "org.apache.commons:commons-lang3:3.5",
 

compiler/build.gradle

@@ -1,17 +1,11 @@
-apply plugin: "cpp"
-apply plugin: "com.google.protobuf"
+plugins {
+    id "cpp"
+
+    id "com.google.protobuf"
+}
 
 description = 'The protoc plugin for gRPC Java'
 
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-        mavenLocal()
-    }
-    dependencies { classpath libraries.protobuf_plugin }
-}
-
 def artifactStagingPath = "$buildDir/artifacts" as File
 // Adds space-delimited arguments from the environment variable env to the
 // argList.

gae-interop-testing/gae-jdk8/build.gradle

@@ -11,7 +11,6 @@
 //  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 //  See the License for the specific language governing permissions and
 //  limitations under the License.
-description = 'gRPC: gae interop testing (jdk8)'
 
 buildscript {
     // Configuration for building
@@ -26,6 +25,13 @@ buildscript {
     }
 }
 
+plugins {
+    id "java"
+    id "war"
+}
+
+description = 'gRPC: gae interop testing (jdk8)'
+
 repositories {
     // repositories for Jar's you access in your code
     mavenLocal()
@@ -34,8 +40,6 @@ repositories {
     jcenter()
 }
 
-apply plugin: 'java'                              // standard Java tasks
-apply plugin: 'war'                               // standard Web Archive plugin
 apply plugin: 'com.google.cloud.tools.appengine'  // App Engine tasks
 
 dependencies {

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

grpclb/build.gradle

@@ -1,13 +1,9 @@
-description = "gRPC: GRPCLB LoadBalancer plugin"
-
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
+plugins {
+    id "com.google.protobuf"
 }
 
+description = "gRPC: GRPCLB LoadBalancer plugin"
+
 dependencies {
     compile project(':grpc-core'),
             project(':grpc-protobuf'),

interop-testing/build.gradle

@@ -1,17 +1,12 @@
-apply plugin: 'application'
+plugins {
+    id "application"
+
+    id "com.google.protobuf"
+}
 
 description = "gRPC: Integration Testing"
 startScripts.enabled = false
 
-// Add dependency on the protobuf plugin
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
-}
-
 dependencies {
     compile project(':grpc-alts'),
             project(':grpc-auth'),

netty/shaded/build.gradle

@@ -1,10 +1,7 @@
-buildscript {
-    repositories { jcenter() }
-    dependencies { classpath 'com.github.jengelman.gradle.plugins:shadow:2.0.4' }
+plugins {
+    id "com.github.johnrengelman.shadow"
 }
 
-apply plugin: 'com.github.johnrengelman.shadow'
-
 description = "gRPC: Netty Shaded"
 
 sourceSets { testShadow {} }

protobuf-lite/build.gradle

@@ -1,14 +1,7 @@
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-        mavenLocal()
-    }
-    dependencies { classpath libraries.protobuf_plugin }
+plugins {
+    id "com.google.protobuf"
 }
 
-apply plugin: 'com.google.protobuf'
-
 description = 'gRPC: Protobuf Lite'
 
 dependencies {

protobuf/build.gradle

@@ -1,13 +1,9 @@
-description = 'gRPC: Protobuf'
-
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
+plugins {
+    id "com.google.protobuf"
 }
 
+description = 'gRPC: Protobuf'
+
 dependencies {
     compile project(':grpc-api'),
             libraries.protobuf

services/build.gradle

@@ -1,10 +1,5 @@
-// Add dependency on the protobuf plugin
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
+plugins {
+    id "com.google.protobuf"
 }
 
 description = "gRPC: Services"

settings.gradle

@@ -1,3 +1,16 @@
+pluginManagement {
+    plugins {
+        id "com.github.johnrengelman.shadow" version "2.0.4"
+        id "com.github.kt3k.coveralls" version "2.0.1"
+        id "com.google.osdetector" version "1.4.0"
+        id "com.google.protobuf" version "0.8.8"
+        id "me.champeau.gradle.japicmp" version "0.2.5"
+        id "me.champeau.gradle.jmh" version "0.4.5"
+        id "net.ltgt.errorprone" version "0.8.1"
+        id "ru.vyarus.animalsniffer" version "1.5.0"
+    }
+}
+
 rootProject.name = "grpc"
 include ":grpc-api"
 include ":grpc-core"

testing-proto/build.gradle

@@ -1,14 +1,9 @@
-description = "gRPC: Testing Protos"
-
-// Add dependency on the protobuf plugin
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-    }
-    dependencies { classpath libraries.protobuf_plugin }
+plugins {
+    id "com.google.protobuf"
 }
 
+description = "gRPC: Testing Protos"
+
 dependencies {
     compile project(':grpc-protobuf'),
             project(':grpc-stub')

xds/build.gradle

@@ -1,18 +1,8 @@
-// Add dependency on the protobuf plugin
-buildscript {
-    repositories {
-        maven { // The google mirror is less flaky than mavenCentral()
-            url "https://maven-central.storage-download.googleapis.com/repos/central/data/" }
-        gradlePluginPortal()
-    }
-    dependencies {
-        classpath libraries.protobuf_plugin
-        classpath 'com.github.jengelman.gradle.plugins:shadow:2.0.4'
-    }
+plugins {
+    id "com.github.johnrengelman.shadow"
+    id "com.google.protobuf"
 }
 
-apply plugin: 'com.github.johnrengelman.shadow'
-
 description = "gRPC: XDS plugin"
 
 [compileJava].each() {
@@ -42,7 +32,6 @@ dependencies {
     signature "org.codehaus.mojo.signature:java17:1.0@signature"
 }
 
-apply plugin: 'com.google.protobuf'
 sourceSets {
     main {
         proto {