7068902: (javac) allow enabling or disabling of String folding

Contributed by netbeans team, modified to suit by the langtools team.

Reviewed-by: jjg, mcimadamore

langtools/src/share/classes/com/sun/tools/javac/parser/JavacParser.java

@@ -57,7 +57,7 @@ public class JavacParser implements Parser {
 
     /** The scanner used for lexical analysis.
      */
-    private Lexer S;
+    protected Lexer S;
 
     /** The factory to be used for abstract syntax tree construction.
      */
@@ -99,9 +99,9 @@ public class JavacParser implements Parser {
         this.allowTWR = source.allowTryWithResources();
         this.allowDiamond = source.allowDiamond();
         this.allowMulticatch = source.allowMulticatch();
+        this.allowStringFolding = fac.options.getBoolean("allowStringFolding", true);
         this.keepDocComments = keepDocComments;
-        if (keepDocComments)
-            docComments = new HashMap<JCTree,String>();
+        docComments = keepDocComments ? new HashMap<JCTree,String>() : null;
         this.keepLineMap = keepLineMap;
         this.errorTree = F.Erroneous();
     }
@@ -146,6 +146,10 @@ public class JavacParser implements Parser {
      */
     boolean allowTWR;
 
+    /** Switch: should we fold strings?
+     */
+    boolean allowStringFolding;
+
     /** Switch: should we keep docComments?
      */
     boolean keepDocComments;
@@ -757,6 +761,8 @@ public class JavacParser implements Parser {
          *  by a single literal representing the concatenated string.
          */
         protected StringBuffer foldStrings(JCTree tree) {
+            if (!allowStringFolding)
+                return null;
             List<String> buf = List.nil();
             while (true) {
                 if (tree.getTag() == JCTree.LITERAL) {

langtools/test/tools/javac/parser/StringFoldingTest.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 7068902
+ * @summary verify that string folding can be enabled or disabled
+ */
+
+import com.sun.source.tree.CompilationUnitTree;
+import com.sun.source.util.JavacTask;
+import java.io.File;
+import java.io.IOException;
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.ToolProvider;
+
+public class StringFoldingTest {
+    final JavaCompiler tool;
+    final JavaSource source;
+
+    public StringFoldingTest() {
+        tool = ToolProvider.getSystemJavaCompiler();
+        source = new JavaSource();
+    }
+
+    static class JavaSource extends SimpleJavaFileObject {
+
+        final static String source =
+                "class C {String X=\"F\" + \"O\" + \"L\" + \"D\" + \"E\" + \"D\";}";
+
+        JavaSource() {
+            super(URI.create("myfo:/C.java"), JavaFileObject.Kind.SOURCE);
+        }
+
+        @Override
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+            return source;
+        }
+    }
+
+    public static void main(String... args) throws IOException {
+        StringFoldingTest t = new StringFoldingTest();
+        t.run(false);
+        t.run(true);
+    }
+
+    void run(boolean disableStringFolding) throws IOException {
+        List<String> argsList = new ArrayList<String>();
+        if (disableStringFolding) {
+            argsList.add("-XDallowStringFolding=false");
+        }
+        JavacTask ct = (JavacTask)tool.getTask(null, null, null,
+                argsList,
+                null,
+                Arrays.asList(source));
+        Iterable<? extends CompilationUnitTree> trees = ct.parse();
+        String text = trees.toString();
+        System.out.println(text);
+
+        if (disableStringFolding) {
+            if (text.contains("FOLDED")) {
+                throw new AssertionError("Expected string folding");
+            }
+        } else {
+            if (!text.contains("FOLDED")) {
+                throw new AssertionError("Expected no string folding");
+            }
+        }
+    }
+}