Issue #21: Report Component

pom.xml

@@ -315,6 +315,11 @@
                                         <branchRate>28</branchRate>
                                         <lineRate>52</lineRate>
                                     </regex>
+                                    <regex>
+                                        <pattern>com.github.checkstyle.regression.report.ReportGenerator</pattern>
+                                        <branchRate>0</branchRate>
+                                        <lineRate>0</lineRate>
+                                    </regex>
                                 </regexes>
                             </check>
                             <instrumentation>

src/main/java/com/github/checkstyle/regression/report/ReportGenerator.java

@@ -0,0 +1,69 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2017 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+////////////////////////////////////////////////////////////////////////////////
+
+package com.github.checkstyle.regression.report;
+
+import java.io.File;
+import java.io.IOException;
+
+/**
+ * Generates the regression diff report.
+ * @author LuoLiangchen
+ */
+public final class ReportGenerator {
+    /** Prevents instantiation. */
+    private ReportGenerator() {
+    }
+
+    /**
+     * Generates the regression diff report.
+     * @param testerPath the path to the directory which holds 'diff.groovy'
+     * @param repoPath   the path to the checkstyle repository
+     * @param branch     the name of the PR branch
+     * @param configFile the generated config file
+     * @return the directory of the generated reports
+     * @throws InterruptedException failure of running CLI
+     * @throws IOException          failure of running CLI
+     */
+    public static File generate(
+            String testerPath, String repoPath, String branch, File configFile)
+            throws InterruptedException, IOException {
+        final Process process = new ProcessBuilder()
+                .directory(new File(testerPath))
+                .command(
+                        "groovy", "diff.groovy",
+                        "-r", repoPath,
+                        "-b", "master",
+                        "-p", branch,
+                        "-c", configFile.getAbsolutePath(),
+                        "-l", "projects-to-test-on.properties"
+                )
+                .inheritIO()
+                .start();
+        final int code = process.waitFor();
+        if (code != 0) {
+            throw new IllegalStateException("an error occurred when running diff.groovy");
+        }
+        final File reportDir = new File(testerPath, "reports/diff");
+        if (!reportDir.exists() || !reportDir.isDirectory()) {
+            throw new IOException("report does not exist or it is not a directory");
+        }
+        return reportDir;
+    }
+}

src/main/java/com/github/checkstyle/regression/report/package-info.java

@@ -0,0 +1,24 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2017 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Contains the regression test runner and the report deployer.
+ * @author LuoLiangchen
+ */
+package com.github.checkstyle.regression.report;

src/test/java/com/github/checkstyle/regression/report/ReportGeneratorTest.java

@@ -0,0 +1,31 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2017 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+////////////////////////////////////////////////////////////////////////////////
+
+package com.github.checkstyle.regression.report;
+
+import static com.github.checkstyle.regression.internal.TestUtils.assertUtilsClassHasPrivateConstructor;
+
+import org.junit.Test;
+
+public class ReportGeneratorTest {
+    @Test
+    public void testIsProperUtilsClass() throws Exception {
+        assertUtilsClassHasPrivateConstructor(ReportGenerator.class);
+    }
+}