Issue #37: extract program

src/main/java/com/github/checkstyle/regression/extract/ExtractInfoProcessor.java

@@ -32,6 +32,7 @@
 import com.google.gson.TypeAdapterFactory;
 import com.google.gson.reflect.TypeToken;
 import com.sun.tools.javac.util.ServiceLoader;
+import com.sun.tools.javac.util.ServiceLoader;
 
 /**
  * Processes the module extract info grabbed from checkstyle project.

src/main/resources/com/github/checkstyle/regression/extract/ExtractInfoGeneratorTest.java

@@ -0,0 +1,81 @@
+package com.puppycrawl.tools.checkstyle;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+import org.junit.Test;
+
+import com.puppycrawl.tools.checkstyle.api.RootModule;
+import com.puppycrawl.tools.checkstyle.internal.CheckUtil;
+import com.puppycrawl.tools.checkstyle.utils.ModuleReflectionUtils;
+
+/**
+ * This file would be injected into checkstyle project and invoked by maven command
+ * to generate the module extract info file.
+ * @author LuoLiangchen
+ */
+public class ExtractInfoGeneratorTest {
+    /**
+     * Generates the extract info file named as "checkstyle_modules.json".
+     * @throws IOException failure when generating the file
+     */
+    @Test
+    public void generateExtractInfoFile() throws IOException {
+        final List<Class<?>> modules = new ArrayList<>(CheckUtil.getCheckstyleModules());
+        modules.sort(Comparator.comparing(Class::getSimpleName));
+        final Json.JsonArray moduleJsonArray = new Json.JsonArray();
+        for (Class<?> module : modules) {
+            moduleJsonArray.add(createJsonObjectFromModuleClass(module));
+        }
+        String jsonString = moduleJsonArray.toString();
+        final File output = new File("checkstyle_modules.json");
+        Files.write(output.toPath(), jsonString.getBytes(Charset.forName("UTF-8")),
+                StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
+    }
+
+    /**
+     * Creates Json object for a module from the module class.
+     * @param clazz the given module class
+     * @return the Json object describing the extract info of the module
+     */
+    private static Json.JsonObject createJsonObjectFromModuleClass(Class<?> clazz) {
+        final Json.JsonObject object = new Json.JsonObject();
+
+        final String name = clazz.getSimpleName();
+        final String parent;
+        if (ModuleReflectionUtils.isCheckstyleCheck(clazz)) {
+            parent = "TreeWalker";
+        }
+        else if (RootModule.class.isAssignableFrom(clazz)) {
+            parent = "";
+        }
+        else {
+            parent = "Checker";
+        }
+        object.addProperty("name", name);
+        object.addProperty("packageName", clazz.getPackage().getName());
+        object.addProperty("parent", parent);
+
+        final Json.JsonArray interfaces = new Json.JsonArray();
+        final Json.JsonArray hierarchies = new Json.JsonArray();
+        Arrays.stream(clazz.getInterfaces()).forEach(cls -> interfaces.add(cls.getCanonicalName()));
+        Class<?> superClass = clazz.getSuperclass();
+        while (!Object.class.equals(superClass)) {
+            hierarchies.add(superClass.getCanonicalName());
+            Arrays.stream(superClass.getInterfaces())
+                    .forEach(cls -> interfaces.add(cls.getCanonicalName()));
+            superClass = superClass.getSuperclass();
+        }
+        object.add("interfaces", interfaces);
+        object.add("hierarchies", hierarchies);
+
+        return object;
+    }
+}

src/main/resources/com/github/checkstyle/regression/extract/Json.java

@@ -0,0 +1,114 @@
+package com.puppycrawl.tools.checkstyle;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Our own Json processing classes.
+ * @author LuoLiangchen
+ */
+class Json {
+    /**
+     * Adds indent of the given text.
+     * @param text the text to add indent
+     * @return the result text with indent
+     */
+    private static String addIndent(String text) {
+        return Arrays.stream(text.split("\n"))
+                .map(line -> "  " + line)
+                .collect(Collectors.joining("\n"));
+    }
+
+    /**
+     * Formats the Json object.
+     * @param object the object to format
+     * @return the format result
+     */
+    private static String format(Object object) {
+        if (object instanceof String) {
+            return "\"" + object + "\"";
+        } else {
+            return object.toString();
+        }
+    }
+
+    /** Represents an object type in Json. */
+    public static final class JsonObject {
+        /** Fields of this Json object. */
+        private final List<KeyValue> members = new LinkedList<>();
+
+        /**
+         * Adds a member.
+         * @param key the key of the field
+         * @param value the value of the field
+         */
+        void addProperty(String key, Object value) {
+            add(key, value);
+        }
+
+        /**
+         * Adds a member.
+         * @param key the key of the field
+         * @param value the value of the field
+         */
+        void add(String key, Object value) {
+            members.add(new KeyValue(key, value));
+        }
+
+        @Override
+        public String toString() {
+            final String keyValueLines = members.stream()
+                    .map(Object::toString)
+                    .collect(Collectors.joining(",\n"));
+            return "{\n" + addIndent(keyValueLines) + "\n}";
+        }
+    }
+
+    /** Represents an array type in Json. */
+    public static final class JsonArray {
+        /** Items of this Json array. */
+        private final List<Object> members = new LinkedList<>();
+
+        /**
+         * Adds a member.
+         * @param object the member to add
+         */
+        void add(Object object) {
+            members.add(object);
+        }
+
+        @Override
+        public String toString() {
+            final String membersLines = members.stream()
+                    .map(Json::format)
+                    .collect(Collectors.joining(",\n"));
+            return "[\n" + addIndent(membersLines) + "\n]";
+        }
+    }
+
+    /** Represents a key-value pair in Json object. */
+    private static final class KeyValue {
+        /** The key of the field. */
+        private final String key;
+
+        /** The value of the field. */
+        private final Object value;
+
+        /**
+         * Creates a new instance of KeyValue.
+         * @param key the key of the field
+         * @param value the value of the field
+         */
+        KeyValue(String key, Object value) {
+            this.key = key;
+            this.value = value;
+        }
+
+        @Override
+        public String toString() {
+            return "\"" + key + "\": " + format(value);
+        }
+    }
+}