Use Spotless and .editorconfig for import order normalization instead of Checkstyle

It makes it much simpler to understand the violations,
and it provides automatic fix via ./gradlew spotlessApply

Author: vlsi

.editorconfig

@@ -0,0 +1,47 @@
+root = true
+
+[*]
+trim_trailing_whitespace = true
+insert_final_newline = true
+charset = utf-8
+indent_style = space
+
+[{*.sh,gradlew}]
+end_of_line = lf
+
+[{*.bat,*.cmd}]
+end_of_line = crlf
+
+[{*.kts,*.kt}]
+ij_kotlin_code_style_defaults = KOTLIN_OFFICIAL
+ij_kotlin_name_count_to_use_star_import = 99
+ij_kotlin_name_count_to_use_star_import_for_members = 99
+ij_java_use_single_class_imports = true
+max_line_length = 100
+ij_any_wrap_long_lines = true
+
+[*.java]
+# Doc: https://youtrack.jetbrains.com/issue/IDEA-170643#focus=streamItem-27-3708697.0-0
+# $ means "static"
+ij_java_imports_layout = org.apache.calcite.**,|,org.apache.**,|,au.com.**,|,com.**,|,io.**,|,mondrian.**,|,net.**,|,org.**,|,scala.**,|,java.**,javax.**,|,*,|,$com.**,|,$org.apache.calcite.**,|,$org.apache.**,|,$org.**,|,$java,|,$*
+indent_size = 2
+tab_width = 2
+max_line_length = 100
+ij_any_spaces_around_additive_operators = true
+ij_any_spaces_around_assignment_operators = true
+ij_any_spaces_around_bitwise_operators = true
+ij_any_spaces_around_equality_operators = true
+ij_any_spaces_around_lambda_arrow = true
+ij_any_spaces_around_logical_operators = true
+ij_any_spaces_around_multiplicative_operators = true
+ij_any_spaces_around_relational_operators = true
+ij_any_spaces_around_shift_operators = true
+ij_continuation_indent_size = 4
+ij_java_if_brace_force = always
+ij_java_indent_case_from_switch = false
+ij_java_space_after_colon = true
+ij_java_space_before_colon = true
+ij_java_ternary_operation_signs_on_next_line = true
+ij_java_use_single_class_imports = true
+ij_java_wrap_long_lines = true
+

.gitignore

@@ -1,3 +1,4 @@
+**/.editorconfig
 *~
 /.idea
 *.iml

build.gradle.kts

@@ -27,13 +27,13 @@ import com.github.vlsi.gradle.properties.dsl.toBool
 import com.github.vlsi.gradle.release.RepositoryType
 import de.thetaphi.forbiddenapis.gradle.CheckForbiddenApis
 import de.thetaphi.forbiddenapis.gradle.CheckForbiddenApisExtension
-import org.apache.tools.ant.DirectoryScanner
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 
 plugins {
     publishing
     // Verification
     checkstyle
+    id("com.diffplug.gradle.spotless")
     id("org.nosphere.apache.rat")
     id("com.github.spotbugs")
     id("de.thetaphi.forbiddenapis") apply false
@@ -61,6 +61,7 @@ val lastEditYear by extra(lastEditYear())
 // Do not enable spotbugs by default. Execute it only when -Pspotbugs is present
 val enableSpotBugs = props.bool("spotbugs", default = false)
 val skipCheckstyle by props()
+val skipSpotless by props()
 val skipJavadoc by props()
 val enableMavenLocal by props()
 val enableGradleMetadata by props()
@@ -152,10 +153,34 @@ val javadocAggregate by tasks.registering(Javadoc::class) {
     setDestinationDir(file("$buildDir/docs/javadocAggregate"))
 }
 
+val licenseHeaderFile = file("config/license.header.java")
+
 allprojects {
     group = "org.apache.calcite.avatica"
     version = buildVersion
 
+    if (!skipSpotless) {
+        apply(plugin = "com.diffplug.gradle.spotless")
+        spotless {
+            kotlinGradle {
+                ktlint()
+                trimTrailingWhitespace()
+                endWithNewline()
+            }
+            if (project == rootProject) {
+                // Spotless does not exclude subprojects when using target(...)
+                // So **/*.md is enough to scan all the md files in the codebase
+                // See https://github.com/diffplug/spotless/issues/468
+                format("markdown") {
+                    target("**/*.md")
+                    // Flot is known to have trailing whitespace, so the files
+                    // are kept in their original format (e.g. to simplify diff on library upgrade)
+                    trimTrailingWhitespace()
+                    endWithNewline()
+                }
+            }
+        }
+    }
     if (!skipCheckstyle) {
         apply<CheckstylePlugin>()
         dependencies {
@@ -257,6 +282,37 @@ allprojects {
             }
         }
 
+        if (!skipSpotless) {
+            spotless {
+                java {
+//                    targetExclude(*javaccGeneratedPatterns + "**/test/java/*.java")
+                    licenseHeaderFile(licenseHeaderFile)
+                    importOrder(
+                        "org.apache.calcite.",
+                        "org.apache.",
+                        "au.com.",
+                        "com.",
+                        "io.",
+                        "mondrian.",
+                        "net.",
+                        "org.",
+                        "scala.",
+                        "java",
+                        "",
+                        "static com.",
+                        "static org.apache.calcite.",
+                        "static org.apache.",
+                        "static org.",
+                        "static java",
+                        "static "
+                    )
+                    removeUnusedImports()
+                    trimTrailingWhitespace()
+                    indentWithSpaces(4)
+                    endWithNewline()
+                }
+            }
+        }
         if (enableSpotBugs) {
             apply(plugin = "com.github.spotbugs")
             spotbugs {

config/license.header.java

@@ -0,0 +1,16 @@
+/*
+ * 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.
+ */

core/build.gradle.kts

@@ -16,7 +16,11 @@
  *
  */
 
-import com.google.protobuf.gradle.*
+import com.google.protobuf.gradle.generateProtoTasks
+import com.google.protobuf.gradle.ofSourceSet
+import com.google.protobuf.gradle.proto
+import com.google.protobuf.gradle.protobuf
+import com.google.protobuf.gradle.protoc
 
 plugins {
     `java-library`

core/src/main/java/org/apache/calcite/avatica/remote/AvaticaCommonsHttpClientImpl.java

@@ -57,7 +57,6 @@
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.util.Objects;
-
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLContext;
 

core/src/main/java/org/apache/calcite/avatica/remote/ClientKeytabJaasConf.java

@@ -21,7 +21,6 @@
 
 import java.util.HashMap;
 import java.util.Map;
-
 import javax.security.auth.login.AppConfigurationEntry;
 import javax.security.auth.login.Configuration;
 

core/src/main/java/org/apache/calcite/avatica/remote/DoAsAvaticaHttpClient.java

@@ -18,7 +18,6 @@
 
 import java.security.PrivilegedAction;
 import java.util.Objects;
-
 import javax.security.auth.Subject;
 
 /**

core/src/main/java/org/apache/calcite/avatica/remote/KerberosConnection.java

@@ -28,7 +28,6 @@
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
-
 import javax.security.auth.Subject;
 import javax.security.auth.kerberos.KerberosPrincipal;
 import javax.security.auth.kerberos.KerberosTicket;

core/src/test/java/org/apache/calcite/avatica/remote/KerberosConnectionTest.java

@@ -24,7 +24,6 @@
 import java.io.File;
 import java.util.Locale;
 import java.util.Map.Entry;
-
 import javax.security.auth.Subject;
 import javax.security.auth.login.Configuration;
 import javax.security.auth.login.LoginContext;