Migrate to spotless (#1748)

* Use spotless for formatting / license check

* Apply formatting

* README

* Apply to example

* google-java-format 1.8 for now

* google-java-format 1.7 for now (last supporting Java 8)

CONTRIBUTING.md

@@ -14,28 +14,29 @@ Make sure to review the projects [license](LICENSE) and sign the
 [CNCF CLA](https://identity.linuxfoundation.org/projects/cncf). A signed CLA will be enforced by an
 automatic check once you submit a PR, but you can also sign it after opening your PR.
 
+## Checks
+
+Before submitting a PR, you should make sure the style checks and unit tests pass. You can run these
+with the `check` task.
+
+```bash
+$ ./gradlew check
+```
+
 ## Style guideline
 
 We follow the [Google Java Style Guide](https://google.github.io/styleguide/javaguide.html). 
-Our build will fail if source code is not formatted according to that style.
+Our build will fail if source code is not formatted according to that style. To fix any
+style failures the above [checks](#checks) show, automatically apply the formatting with
+
+```bash
+$ ./gradlew spotlessApply
+```
 
 To verify code style manually run the following command, 
 which uses [google-java-format](https://github.com/google/google-java-format) library:
 
-`./gradlew verifyGoogleJavaFormat`
-
-or on Windows
-
-`gradlew.bat verifyGoogleJavaFormat`
-
-Instead of fixing style inconsistencies by hand, you can run gradle task `googleJavaFormat`
-to automatically fix all found issues:
-
-`./gradlew googleJavaFormat`
-
-or on Windows
-
-`gradlew.bat googleJavaFormat`
+`./gradlew spotless`
 
 ### Pre-commit hook
 To completely delegate code style formatting to the machine, 
@@ -43,11 +44,10 @@ you can add [git pre-commit hook](https://git-scm.com/docs/githooks).
 We provide an example script in `buildscripts/pre-commit` file.
 Just copy or symlink it into `.git/hooks` folder.
 
-
 ### Editorconfig 
 As additional convenience for IntelliJ Idea users, we provide `.editorconfig` file.
 Idea will automatically use it to adjust its code formatting settings.
-It does not support all required rules, so you still have to run `googleJavaFormat` from time to time.
+It does not support all required rules, so you still have to run `spotlessApply` from time to time.
 
 ### Javadoc
 

Makefile

@@ -19,7 +19,7 @@ init-git-submodules:
 
 .PHONY: verify-format
 verify-format:
-	./gradlew verGJF
+	./gradlew spotlessCheck
 
 .PHONY: publish-snapshots
 publish-snapshots:

build.gradle

@@ -1,5 +1,5 @@
 plugins {
-    id "com.github.sherter.google-java-format" apply false
+    id "com.diffplug.spotless" version "5.6.1"
     id "com.jfrog.artifactory" apply false
     id "com.jfrog.bintray" version "1.8.4" apply false // Need *specific* version.
     id "net.ltgt.errorprone" apply false
@@ -137,7 +137,7 @@ configure(opentelemetryProjects) {
     apply plugin: 'signing'
     apply plugin: 'jacoco'
 
-    apply plugin: 'com.github.sherter.google-java-format'
+    apply plugin: 'com.diffplug.spotless'
     apply plugin: 'net.ltgt.errorprone'
 
     repositories {
@@ -299,8 +299,11 @@ configure(opentelemetryProjects) {
 
     jacoco { toolVersion = "0.8.5" }
 
-    googleJavaFormat {
-        toolVersion = '1.7'
+    spotless {
+        java {
+            googleJavaFormat("1.7")
+            licenseHeaderFile rootProject.file('buildscripts/spotless.license.java'), '(package|import|class|// Includes work from:)'
+        }
     }
 
     configurations {
@@ -363,17 +366,7 @@ configure(opentelemetryProjects) {
         addBooleanOption('Xdoclint:all,-missing', true)
     }
 
-    afterEvaluate {  // Allow subproject to add more source sets.
-        tasks.googleJavaFormat {
-            source = sourceSets*.allJava
-            include '**/*.java'
-        }
-
-        tasks.verifyGoogleJavaFormat {
-            source = sourceSets*.allJava
-            include '**/*.java'
-        }
-
+    afterEvaluate {
         jar {
             inputs.property("moduleName", moduleName)
 

buildscripts/checkstyle.license

@@ -1,4 +0,0 @@
-^/\*$
-^ \* Copyright (The OpenTelemetry|\d\d\d\d(-\d\d)?, Guava) Authors$
-^ \* SPDX-License-Identifier: Apache-2.0$
-^ \*/$

buildscripts/checkstyle.xml

@@ -20,12 +20,6 @@
 
     <property name="severity" value="error"/>
 
-
-    <module name="RegexpHeader">
-        <property name="headerFile" value="${rootDir}/buildscripts/checkstyle.license"/>
-        <property name="fileExtensions" value="java"/>
-    </module>
-
     <property name="fileExtensions" value="java, properties, xml"/>
     <!-- Checks for whitespace                               -->
     <!-- See http://checkstyle.sf.net/config_whitespace.html -->

buildscripts/pre-commit

@@ -1,3 +1,3 @@
 #!/usr/bin/env sh
 
-./gradlew googleJavaFormat
+./gradlew spotlessApply

buildscripts/spotless.license.java

@@ -0,0 +1,5 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+

examples/build.gradle

@@ -1,6 +1,5 @@
 plugins {
-    id 'com.github.sherter.google-java-format' apply false
-    id "com.jfrog.artifactory" apply false
+    id "com.diffplug.spotless"
 }
 
 subprojects {
@@ -8,7 +7,7 @@ subprojects {
     apply plugin: 'java'
     apply plugin: 'java-library'
     apply plugin: 'idea'
-    apply plugin: 'com.github.sherter.google-java-format'
+    apply plugin: 'com.diffplug.spotless'
 
     group = "io.opentelemetry"
     version = "0.1.0-SNAPSHOT"
@@ -29,10 +28,11 @@ subprojects {
         }
     }
 
-    googleJavaFormat {
-        toolVersion = '1.7'
+    spotless {
+        java {
+            googleJavaFormat("1.7")
+        }
     }
-    compileJava.dependsOn(verifyGoogleJavaFormat)
 
     //create a single Jar with all dependencies
     task fatJar(type: Jar) {

examples/settings.gradle

@@ -1,7 +1,6 @@
 pluginManagement {
     plugins {
-        id 'com.github.sherter.google-java-format' version "0.8"
-        id "com.jfrog.artifactory" version "4.13.0"
+        id "com.diffplug.spotless" version "5.6.1"
         id 'com.google.protobuf' version '0.8.8'
     }
 

extensions/trace_propagators/src/main/java/io/opentelemetry/extensions/trace/propagation/StringUtils.java

@@ -1,3 +1,9 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// Includes work from:
 /*
  * Copyright 2010, Guava Authors
  * SPDX-License-Identifier: Apache-2.0

settings.gradle

@@ -1,8 +1,8 @@
 pluginManagement {
     plugins {
+        id "com.diffplug.spotless" version "5.6.1"
         id "com.github.ben-manes.versions" version "0.20.0"
         id "com.github.kt3k.coveralls" version "2.0.1"
-        id 'com.github.sherter.google-java-format' version "0.8"
         id "com.google.protobuf" version "0.8.8"
         id "com.jfrog.artifactory" version "4.13.0"
         id "io.morethan.jmhreport" version "0.9.0"