Add codestyle checks to fail for inconsistent codestyles

Author: janniklinde

dev/checkstyle/checkstyle.xml

@@ -0,0 +1,74 @@
+<?xml version="1.0"?>
+<!--
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, 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.
+-->
+
+<!DOCTYPE module PUBLIC
+        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+        "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<module name="Checker">
+    <module name="SuppressionFilter">
+        <property name="file" value="dev/checkstyle/suppressions.xml"/>
+    </module>
+
+    <module name="TreeWalker">
+        <!-- XPath-based suppressions (target specific AST patterns) -->
+        <module name="SuppressionXpathFilter">
+            <property name="file" value="dev/checkstyle/suppressions-xpath.xml"/>
+        </module>
+
+        <module name="UnusedImports"/>
+        <module name="RedundantImport"/>
+        <module name="AvoidStarImport"/>
+        <module name="IllegalImport"/>
+        <module name="PackageName"/>
+        <module name="TypeName"/>
+        <!-- 1) Private fields must be _lowerCamelCase -->
+        <!--<module name="MemberName">
+            <property name="applyToPublic" value="false"/>
+            <property name="applyToProtected" value="false"/>
+            <property name="applyToPackage" value="false"/>
+            <property name="applyToPrivate" value="true"/>
+
+            <property name="format" value="^_[a-z][a-zA-Z0-9]*$"/>
+        </module>-->
+        <!-- 2) Non-private fields must be lowerCamelCase (no leading underscore) -->
+        <!--<module name="MemberName">
+            <property name="applyToPublic" value="true"/>
+            <property name="applyToProtected" value="false"/>
+            <property name="applyToPackage" value="true"/>
+            <property name="applyToPrivate" value="false"/>
+            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
+        </module>-->
+        <module name="MethodName"/>
+        <!--<module name="ParameterName"/>-->
+        <module name="LocalVariableName">
+            <property name="format"
+                      value="^[a-zA-Z][a-zA-Z0-9_]*$"/>
+        </module>
+    </module>
+
+    <!-- to detect leading spaces (should be tabs) -->
+    <module name="RegexpMultiline">
+        <property name="format"
+                  value="(?m)^( +)(?!\*)(?!//)(?!/\*)\S"/>
+        <property name="message"
+                  value="Indentation must use tabs (no leading spaces)."/>
+    </module>
+</module>

dev/checkstyle/suppressions-xpath.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0"?>
+<!--
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, 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.
+-->
+
+<!DOCTYPE suppressions PUBLIC
+        "-//Checkstyle//DTD SuppressionXpathFilter Experimental Configuration 1.2//EN"
+        "https://checkstyle.org/dtds/suppressions_1_2_xpath_experimental.dtd">
+
+<suppressions>
+    <!-- Suppress MemberName for private final fields -->
+    <suppress-xpath
+            checks="MemberNameCheck"
+            query="//VARIABLE_DEF[
+                     ./MODIFIERS/LITERAL_PRIVATE
+                     and ./MODIFIERS/FINAL
+                   ]/IDENT"/>
+
+    <!-- Suppress MemberName for private static fields -->
+    <suppress-xpath
+            checks="MemberNameCheck"
+            query="//VARIABLE_DEF[
+                     ./MODIFIERS/LITERAL_PRIVATE
+                     and ./MODIFIERS/LITERAL_STATIC
+                   ]/IDENT"/>
+</suppressions>