From 44e822ed86049ab30b20c9c6e47571eb76b80d51 Mon Sep 17 00:00:00 2001
From: gbrodman <gbrodman@google.com>
Date: Mon, 28 Jan 2019 13:57:32 -0800
Subject: [PATCH] Add Checkstyle and Error Prone to the Gradle build

We make some modifications to the internal Google checkstyle file because Google's linter uses a modified build of Checkstyle that introduces some new classes and allows for more specific checks than the open-source Checkstyle (e.g. only enforcing UPPER_SNAKE_CASE on deeply immutable fields). There exists a public Checkstyle file that purports to be the Google java format file (https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml) but it doesn't quite match up with what the internal linter says in certain situations (e.g. what operators must/can appear on new lines).

The suppressions are basically "don't run on generated code + don't care about Javadoc in test code"

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=231283700
---
 gradle/build.gradle                       |  24 +++
 gradle/config/checkstyle/checkstyle.xml   | 251 ++++++++++++++++++++++
 gradle/config/checkstyle/suppressions.xml |  12 ++
 3 files changed, 287 insertions(+)
 create mode 100644 gradle/config/checkstyle/checkstyle.xml
 create mode 100644 gradle/config/checkstyle/suppressions.xml

diff --git a/gradle/build.gradle b/gradle/build.gradle
index 874108451..f76ba710c 100644
--- a/gradle/build.gradle
+++ b/gradle/build.gradle
@@ -6,6 +6,7 @@ buildscript {
 
   dependencies {
     classpath 'com.google.cloud.tools:appengine-gradle-plugin:1.3.3'
+    classpath "net.ltgt.gradle:gradle-errorprone-plugin:0.6.1"
     classpath 'org.sonatype.aether:aether-api:1.13.1'
     classpath 'org.sonatype.aether:aether-impl:1.13.1'
   }
@@ -18,6 +19,8 @@ plugins {
   // Ensures that source code is generated at an appropriate location.
   id 'net.ltgt.apt' version '0.19' apply false
   id 'com.bmuschko.docker-java-application' version '4.0.4' apply false
+  id 'net.ltgt.errorprone' version '0.6.1'
+  id 'checkstyle'
 }
 
 apply from: 'dependencies.gradle'
@@ -104,6 +107,27 @@ subprojects {
   apply plugin: 'nebula.dependency-lock'
   apply plugin: 'nebula.lint'
   apply plugin: 'net.ltgt.apt'
+  apply plugin: 'net.ltgt.errorprone'
+  apply plugin: 'checkstyle'
+
+  // Checkstyle should run as part of the testing task
+  tasks.test.dependsOn tasks.checkstyleMain
+  tasks.test.dependsOn tasks.checkstyleTest
+
+  dependencies {
+    // compatibility with Java 8
+    errorproneJavac("com.google.errorprone:javac:9+181-r4173-1")
+    errorprone("com.google.errorprone:error_prone_core:2.3.2")
+  }
+
+  tasks.withType(JavaCompile).configureEach {
+    options.compilerArgs << "-Werror"
+    options.errorprone.disableWarningsInGeneratedCode = true
+    options.errorprone.errorproneArgumentProviders.add([
+            asArguments: {
+              return ['-XepExcludedPaths:.*/build/generated/.*']
+            }] as CommandLineArgumentProvider)
+  }
 
   version = '1.0'
   sourceCompatibility = '1.8'
diff --git a/gradle/config/checkstyle/checkstyle.xml b/gradle/config/checkstyle/checkstyle.xml
new file mode 100644
index 000000000..5e8d60967
--- /dev/null
+++ b/gradle/config/checkstyle/checkstyle.xml
@@ -0,0 +1,251 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE module PUBLIC
+    "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
+    "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<!-- This is a checkstyle configuration file. For descriptions of
+what the following rules do, please see the checkstyle configuration
+page at http://checkstyle.sourceforge.net/config.html -->
+
+<!-- Checks with numbered comments refer to recommendations made
+by Joshua Bloch in his book Effective Java -->
+
+<module name="Checker">
+  <module name="SuppressionFilter"> <!-- baseline-gradle: README.md -->
+      <property name="file" value="${config_loc}/suppressions.xml"/>
+  </module>
+  <property name="charset" value="UTF-8"/>
+  <module name="FileTabCharacter">
+    <!-- Checks that there are no tab characters in the file.-->
+  </module>
+
+  <module name="RegexpSingleline">
+    <!-- Checks that FIXME is not used in comments.  TODO is preferred. -->
+    <property name="format" value="((//.*)|(\*.*))FIXME" />
+    <property name="message" value='TODO is preferred to FIXME.  e.g. "TODO(johndoe): Refactor when v2 is released."' />
+  </module>
+
+
+  <!-- All Java AST specific tests live under TreeWalker module. -->
+  <module name="TreeWalker">
+
+    <!--
+    IMPORT CHECKS
+    -->
+
+    <module name="RedundantImport">
+      <property name="severity" value="error"/>
+    </module>
+
+    <module name="AvoidStarImport">
+      <property name="severity" value="error"/>
+    </module>
+
+    <module name="UnusedImports">
+      <!-- DPL is a notable violator of this rule. -->
+      <property name="severity" value="error"/>
+      <!-- Imports used only in Javadoc are tolerated. See http://b/838496 -->
+      <property name="processJavadoc" value="true"/>
+      <message key="import.unused" value="Unused import: {0}." />
+    </module>
+
+    <module name="ImportOrder">
+      <!-- Checks for out of order import statements. -->
+      <metadata name="altname" value="ImportOrder"/>
+      <property name="severity" value="warning"/>
+      <!-- This ensures that static imports go first. -->
+      <property name="option" value="top"/>
+      <property name="tokens" value="STATIC_IMPORT, IMPORT"/>
+      <property name="separatedStaticGroups" value="true"/>
+      <property name="sortStaticImportsAlphabetically" value="true"/>
+      <message key="import.ordering" value="Wrong order for {0} import."/>
+    </module>
+
+    <!--
+    JAVADOC CHECKS
+    -->
+
+    <module name="JavadocTypeCheck">
+      <!-- Item 28 - Write doc comments for all exposed API elements. -->
+      <!-- Ensure all classes with visibility greater than or equal to
+        protected have class level documentation. -->
+      <property name="scope" value="protected"/>
+      <property name="severity" value="error"/>
+      <!-- Style guide doesn't prohibit custom tags. Typos will be caught by other tools. -->
+      <property name="allowUnknownTags" value="true"/>
+      <property name="allowMissingParamTags" value="true"/>
+      <message key="javadoc.missing" value="Missing a Javadoc comment."/>
+    </module>
+
+    <!--
+    NAMING CHECKS
+    -->
+
+    <!-- Item 38 - Adhere to generally accepted naming conventions -->
+    <module name="PackageName">
+      <!-- Validates identifiers for package names against the
+        supplied expression. -->
+      <property name="format" value="^([a-z][a-z0-9]*)(\.[a-z][a-z0-9]*)*$"/>
+      <property name="severity" value="warning"/>
+    </module>
+
+    <module name="TypeNameCheck">
+      <!-- Validates static, final fields against the supplied expression. -->
+      <metadata name="altname" value="TypeName"/>
+      <property name="severity" value="warning"/>
+      <property name="format" value="^[A-Z][a-zA-Z0-9]*(_CustomFieldSerializer)?$"/>
+    </module>
+
+   <module name="MemberNameCheck">
+      <!-- Validates non-static members against the supplied expression. -->
+      <metadata name="altname" value="MemberName"/>
+      <property name="applyToPublic" value="true"/>
+      <property name="applyToProtected" value="true"/>
+      <property name="applyToPackage" value="true"/>
+      <property name="applyToPrivate" value="true"/>
+      <!-- allows for googles deprecated foo_ member naming scheme -->
+      <property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>
+      <property name="severity" value="warning"/>
+    </module>
+
+    <module name="MethodNameCheck">
+      <!-- Validates identifiers for method names. -->
+      <metadata name="altname" value="MethodName"/>
+      <property name="format" value="^([a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*|__constructor__|__staticInitializer__)$"/>
+      <property name="severity" value="warning"/>
+    </module>
+
+    <module name="ParameterName">
+      <!-- Validates identifiers for method parameters against the
+        expression "^[a-z][a-zA-Z0-9]*$". -->
+      <property name="severity" value="warning"/>
+    </module>
+
+    <module name="LocalFinalVariableName">
+      <!-- Validates identifiers for local final variables against the
+        expression "^[a-z][a-zA-Z0-9]*$". -->
+      <property name="severity" value="warning"/>
+    </module>
+
+    <module name="LocalVariableName">
+      <!-- Validates identifiers for local variables against the
+        expression "^[a-z][a-zA-Z0-9]*$". -->
+      <property name="severity" value="warning"/>
+    </module>
+
+    <!--
+    LENGTH and CODING CHECKS
+    -->
+
+    <module name="LineLength">
+      <!-- Checks if a line is too long. -->
+      <property name="max" value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.max}" default="100"/>
+      <property name="severity" value="error"/>
+
+      <!-- Ignore lines that have any series of 80 or more non-whitespace characters.
+      These lines likely cannot be broken.
+      -->
+      <property name="ignorePattern"
+          value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.ignorePattern}"
+          default=".*[^ ]{80,}.*"/>
+    </module>
+
+    <module name="OperatorWrap">
+      <property name="option" value="nl"/>
+      <property name="tokens" value="QUESTION, EQUAL, NOT_EQUAL, DIV, PLUS, MINUS, STAR, MOD, SR, BSR, GE, GT, SL, LE, LT, BXOR, BOR, LOR, BAND, LAND, TYPE_EXTENSION_AND, LITERAL_INSTANCEOF"/>
+    </module>
+
+    <module name="LeftCurly">
+      <!-- Checks for placement of the left curly brace ('{'). -->
+      <property name="severity" value="warning"/>
+    </module>
+
+    <module name="RightCurly">
+      <property name="option" value="same"/>
+      <property name="severity" value="warning"/>
+    </module>
+
+    <!-- Checks for braces around if and else blocks -->
+    <module name="NeedBraces">
+      <property name="severity" value="warning"/>
+      <property name="tokens" value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>
+    </module>
+
+    <!-- Checks for empty catch blocks in non-test files. -->
+    <module name="EmptyCatchBlock">
+      <property name="exceptionVariableName" value="expected"/>
+      <property name="severity" value="error"/>
+      <message key="catchBlock.empty"
+               value="Empty catch blocks are not allowed. If this is an expected exception, it should be named 'expected'."/>
+    </module>
+
+    <!--
+    MODIFIERS CHECKS
+    -->
+
+    <module name="ModifierOrder">
+      <!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and
+           8.4.3.  The prescribed order is:
+           public, protected, private, abstract, static, final, transient, volatile,
+           synchronized, native, strictfp
+        -->
+    </module>
+
+    <!--
+    WHITESPACE CHECKS
+    -->
+
+    <module name="WhitespaceAround">
+      <!-- Checks that various tokens are surrounded by whitespace.
+           This includes most binary operators and keywords followed
+           by regular or curly braces.
+      -->
+      <property name="tokens" value="ASSIGN, BAND, BAND_ASSIGN, BOR,
+        BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN,
+        EQUAL, GE, GT, LAND, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE,
+        LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN,
+        LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS,
+        MINUS_ASSIGN, MOD, MOD_ASSIGN, NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION,
+        SL, SL_ASSIGN, SR_ASSIGN, STAR, STAR_ASSIGN"/>
+      <property name="severity" value="error"/>
+      <property name="ignoreEnhancedForColon" value="false"/>
+    </module>
+
+    <module name="WhitespaceAfter">
+      <!-- Checks that commas, semicolons and typecasts are followed by
+           whitespace.
+      -->
+      <property name="tokens" value="COMMA, SEMI, TYPECAST"/>
+    </module>
+
+    <module name="NoWhitespaceAfter">
+      <!-- Checks that there is no whitespace after various unary operators.
+           Linebreaks are allowed.
+      -->
+      <property name="tokens" value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS,
+        UNARY_PLUS"/>
+      <property name="allowLineBreaks" value="true"/>
+      <property name="severity" value="error"/>
+    </module>
+
+    <module name="NoWhitespaceBefore">
+      <!-- Checks that there is no whitespace before various unary operators.
+           Linebreaks are allowed.
+      -->
+      <property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC"/>
+      <property name="allowLineBreaks" value="true"/>
+      <property name="severity" value="error"/>
+    </module>
+
+    <module name="ParenPad">
+      <!-- Checks that there is no whitespace before close parens or after
+           open parens. Allows whitespace after open parens if it is followed
+           by the end of a line or by the start of a comment. Allows whitespace
+           before close parens if it is preceeded by the start of a line or by
+           the end of a block comment.
+      -->
+      <metadata name="altname" value="ParenPad"/>
+      <property name="severity" value="warning"/>
+    </module>
+  </module>
+</module>
diff --git a/gradle/config/checkstyle/suppressions.xml b/gradle/config/checkstyle/suppressions.xml
new file mode 100644
index 000000000..549987a53
--- /dev/null
+++ b/gradle/config/checkstyle/suppressions.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+
+<!DOCTYPE suppressions PUBLIC
+    "-//Puppy Crawl//DTD Suppressions 1.1//EN"
+    "http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+
+<suppressions>
+  <!-- Ignore generated files in Checkstyle -->
+  <suppress files="[/\\].*[/\\]generated.*[/\\]" checks="."/>
+  <!-- Ignore Javadoc checks in test files -->
+  <suppress files="[/\\].*[/\\]javatests.*[/\\]" checks="JavadocType"/>
+</suppressions>