Issue checkstyle#37: extract program

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

@@ -0,0 +1,83 @@
+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.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+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 Gson gson = new GsonBuilder().setPrettyPrinting().create();
+        final List<JsonObject> objects = CheckUtil.getCheckstyleModules().stream()
+                .map(ExtractInfoGeneratorTest::createJsonObjectFromModuleClass)
+                .collect(Collectors.toList());
+        objects.sort(Comparator.comparing(obj -> obj.get("name").getAsString()));
+        String jsonString = gson.toJson(objects);
+        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 JsonObject createJsonObjectFromModuleClass(Class<?> clazz) {
+        final JsonObject object = new JsonObject();
+
+        final String name = clazz.getSimpleName();
+        final String parent;
+        if (ModuleReflectionUtils.isCheckstyleCheck(clazz)) {
+            parent = "TreeWalker";
+        }
+        else if ("Checker".equals(name)) {
+            parent = "";
+        }
+        else {
+            parent = "Checker";
+        }
+        object.addProperty("name", name);
+        object.addProperty("packageName", clazz.getPackage().getName());
+        object.addProperty("parent", parent);
+
+        final JsonArray interfaces = new JsonArray();
+        final JsonArray hierarchies = new 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;
+    }
+}