Issue checkstyle#3839: Added 3 methods to help detect empty LITERAL_C…

…ASE. Added corresponding UTs

src/main/java/com/puppycrawl/tools/checkstyle/checks/blocks/EmptyBlockCheck.java

@@ -171,6 +171,10 @@ else if (!hasText(leftCurly)) {
                     ast.getText());
             }
         }
+
+        if (ast.getType() == TokenTypes.LITERAL_CASE) {
+            checkForEmptyCase(ast);
+        }
     }
 
     /**
@@ -236,4 +240,72 @@ private static boolean checkIsAllLinesAreWhitespace(String[] lines, int lineFrom
         }
         return result;
     }
+
+    /**
+     *  Checks for empty LITERAL_CASE.
+     *
+     *  @param ast a {@code DetailAST} value
+     */
+    protected void checkForEmptyCase(DetailAST ast) {
+        final DetailAST slistToken = ast.getNextSibling();
+        if (slistToken != null
+                && slistToken.getType() == TokenTypes.SLIST) {
+            if (option == BlockOption.STMT) {
+                if (!isCaseHavingStmt(slistToken)) {
+                    log(ast.getLineNo(),
+                            ast.getColumnNo(),
+                            MSG_KEY_BLOCK_NO_STMT,
+                            ast.getText());
+                }
+            }
+            else if (!isCaseHavingText(slistToken)) {
+                log(ast.getLineNo(),
+                        ast.getColumnNo(),
+                        MSG_KEY_BLOCK_EMPTY,
+                        ast.getText());
+            }
+        }
+    }
+
+    /**
+     * Checks if case has any statements.
+     *
+     * @param slistAST a {@code DetailAST} value
+     * @return true if the case related to the SLIST token has atleast one statement
+     */
+    protected boolean isCaseHavingStmt(final DetailAST slistAST) {
+        DetailAST leftCurly;
+        for (leftCurly = slistAST.getFirstChild();
+             leftCurly != null; leftCurly = leftCurly.getNextSibling()) {
+            if (leftCurly.getFirstChild().getType() != TokenTypes.RCURLY) {
+                break;
+            }
+        }
+        return leftCurly != null;
+    }
+
+    /**
+     * Checks if case has any text.
+     *
+     * @param slistAST a {@code DetailAST} value
+     * @return true if the case related to the SLIST token has any text
+     */
+    protected boolean isCaseHavingText(final DetailAST slistAST) {
+        boolean returnValue = true;
+        for (DetailAST leftCurly = slistAST.getFirstChild();
+             leftCurly != null; leftCurly = leftCurly.getNextSibling()) {
+            if (leftCurly.getType() == TokenTypes.SLIST) {
+                returnValue = hasText(leftCurly);
+            }
+            else {
+                returnValue = true;
+            }
+
+            if (returnValue) {
+                break;
+            }
+        }
+        return returnValue;
+    }
+
 }

src/test/java/com/puppycrawl/tools/checkstyle/checks/blocks/EmptyBlockCheckTest.java

@@ -157,4 +157,36 @@ public void testInvalidOption() throws Exception {
                             + "Cannot set property 'option' to 'invalid_option' in module"));
         }
     }
+
+    @Test
+    public void testAllowEmptyCaseWithText() throws Exception {
+        final DefaultConfiguration checkConfig = createCheckConfig(EmptyBlockCheck.class);
+        checkConfig.addAttribute("option", BlockOption.TEXT.toString());
+        checkConfig.addAttribute("tokens", "LITERAL_CASE");
+        final String[] expected = {
+            "12:21: " + getCheckMessage(MSG_KEY_BLOCK_EMPTY, "case"),
+            "17:13: " + getCheckMessage(MSG_KEY_BLOCK_EMPTY, "case"),
+            "29:21: " + getCheckMessage(MSG_KEY_BLOCK_EMPTY, "case"),
+            "31:29: " + getCheckMessage(MSG_KEY_BLOCK_EMPTY, "case"),
+            "32:21: " + getCheckMessage(MSG_KEY_BLOCK_EMPTY, "case"),
+        };
+        verify(checkConfig, getPath("InputEmptyCase.java"), expected);
+    }
+
+    @Test
+    public void testForbidCaseWithoutStmt() throws Exception {
+        final DefaultConfiguration checkConfig = createCheckConfig(EmptyBlockCheck.class);
+        checkConfig.addAttribute("option", BlockOption.STMT.toString());
+        checkConfig.addAttribute("tokens", "LITERAL_CASE");
+        final String[] expected = {
+            "12:21: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+            "17:13: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+            "21:13: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+            "29:21: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+            "31:29: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+            "32:21: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+            "32:32: " + getCheckMessage(MSG_KEY_BLOCK_NO_STMT, "case"),
+        };
+        verify(checkConfig, getPath("InputEmptyCase.java"), expected);
+    }
 }

src/test/resources/com/puppycrawl/tools/checkstyle/checks/blocks/InputEmptyCase.java

@@ -0,0 +1,36 @@
+////////////////////////////////////////////////////////////////////////////////
+// Input test file for testing empty LITERAL_CASE.
+// Created: 2017
+////////////////////////////////////////////////////////////////////////////////
+package com.puppycrawl.tools.checkstyle.checks.blocks;
+
+class InputEmptyCase
+{
+    void method1(int a) {
+        switch (a) {}
+        switch (a) {case 1:}
+        switch (a) {case 1:{}} // 1 violation
+        switch (a) {
+            case 1:
+        }
+        switch (a) {
+            case 1: // 1 violation
+            {}
+        }
+        switch (a) {
+            case 1: // 1 violation if checking statements
+            {// none if checking text
+            }
+        }
+    }
+
+    public void method2(char c) {
+        switch(c) { case 0: } // no violation
+        switch(c) { case 0: {} } // 1 violation
+        switch(c) { case 0: method1(0); {} } // no violation
+        switch(c) { case 0: case 1: {} } // 1 violation
+        switch(c) { case 0: {} case 1: {// 2 violations if checking statements
+        }
+        }
+    }
+}