Reduce sourcemap size by including newlines in statements

For pretty-printed statement blocks, include the following newline
within each statement range. Also added more tests.

This reduces sourcemap size by about 20% uncompressed and 40%
compressed. (Combined with [1], the total is 76% reduction
uncompressed and 72% compressed.)

[1] https://gwt-review.googlesource.com/#/c/7174/

Change-Id: I71651e83b8eee2355190b7b5034d7c9643a13781

Author: Brian Slesinsky

dev/core/src/com/google/gwt/dev/js/JsToStringGenerationVisitor.java

@@ -935,6 +935,7 @@ protected void printJsBlock(JsBlock x, boolean truncate, boolean finalNewline) {
             _semi();
           }
           _newlineOpt();
+          billChildToHere();
         }
       }
       if (shouldRecordPositions) {

dev/core/test/com/google/gwt/dev/js/JsReportGenerationVisitorTest.java

@@ -23,7 +23,6 @@
 import com.google.gwt.dev.js.ast.JsProgram;
 import com.google.gwt.dev.js.ast.JsStatement;
 import com.google.gwt.dev.util.DefaultTextOutput;
-import com.google.gwt.thirdparty.guava.common.base.Joiner;
 import com.google.gwt.thirdparty.guava.common.collect.Lists;
 
 import junit.framework.TestCase;
@@ -38,6 +37,7 @@
  * JavaScript. (Doesn't check that they point to the right place.)
  */
 public class JsReportGenerationVisitorTest extends TestCase {
+  boolean compact = false;
   JsProgram program;
 
   // TODO(skybrian) don't generate ranges for all of these nodes. Just do executable code.
@@ -51,13 +51,14 @@ public void testEmpty() throws Exception {
   public void testOneStatement() throws Exception {
     program = parseJs("x = 1");
     checkMappings(
-        "x=1;",
+        "x = 1;\n",
         "x",
         "1"
     );
   }
 
-  public void testTwoStatements() throws Exception {
+  public void testTwoStatementsCompact() throws Exception {
+    compact = true;
     program = parseJs("x = 1; y = 2");
     checkMappings(
         "x=1;y=2;",
@@ -70,7 +71,21 @@ public void testTwoStatements() throws Exception {
     );
   }
 
-  public void testIfStatement() throws Exception {
+  public void testTwoStatementsPretty() throws Exception {
+    program = parseJs("x = 1; y = 2");
+    checkMappings(
+        "x = 1;\ny = 2;\n",
+        "x = 1;\n",
+        "x",
+        "1",
+        "y = 2;\n",
+        "y",
+        "2"
+    );
+  }
+
+  public void testIfStatementCompact() throws Exception {
+    compact = true;
     program = parseJs("if(true) { x=1 } else { y=2 }");
     checkMappings(
         "if(true){x=1}else{y=2}",
@@ -86,6 +101,44 @@ public void testIfStatement() throws Exception {
     );
   }
 
+  public void testIfStatementPretty() throws Exception {
+    program = parseJs("if(true) { x=1 } else { y=2 }");
+    checkMappings(
+        "if (true) {\n  x = 1;\n}\n else {\n  y = 2;\n}\n",
+        "true",
+        "{\n  x = 1;\n}\n",
+        "  x = 1;\n",
+        "  x",
+        "1",
+        "{\n  y = 2;\n}\n",
+        "  y = 2;\n",
+        "  y",
+        "2"
+    );
+  }
+
+  public void testFunctionCompact() throws Exception {
+    compact = true;
+    program = parseJs("function f() { return 42; }");
+    checkMappings("function f(){return 42}\n",
+        "function f(){return 42}",
+        "{return 42}",
+        "return 42",
+        "42"
+    );
+  }
+
+  public void testFunctionPretty() throws Exception {
+    program = parseJs("function f() { return 42; }");
+    checkMappings(
+      "function f(){\n  return 42;\n}\n\n",
+      "function f(){\n  return 42;\n}\n",
+      "{\n  return 42;\n}\n",
+      "  return 42;\n",
+      "42"
+    );
+  }
+
   private JsProgram parseJs(String js) throws IOException, JsParserException {
     JsProgram program = new JsProgram();
     SourceInfo info = SourceOrigin.create(0, js.length(), 123, "test.js");
@@ -97,14 +150,20 @@ private JsProgram parseJs(String js) throws IOException, JsParserException {
 
   private void checkMappings(String ...expectedLines)
       throws IOException, JsParserException {
-    DefaultTextOutput text = new DefaultTextOutput(true);
+    DefaultTextOutput text = new DefaultTextOutput(compact);
     JsReportGenerationVisitor generator = new JsReportGenerationVisitor(text,
         JavaToJavaScriptMap.EMPTY);
     generator.accept(program);
     String actual = dumpMappings(text.toString(), generator.getSourceInfoMap());
 
-    String expected = expectedLines.length == 0 ? "" : Joiner.on("\n").join(expectedLines) + "\n";
-    assertEquals("Mappings:\n" + expected, actual);
+    StringBuilder expected = new StringBuilder();
+    expected.append("Mappings:\n");
+    for (String line : expectedLines) {
+      expected.append(escape(line));
+      expected.append("\n");
+    }
+
+    assertEquals(expected.toString(), actual);
   }
 
   private String dumpMappings(String javascript, JsSourceMap mappings) {
@@ -115,9 +174,16 @@ private String dumpMappings(String javascript, JsSourceMap mappings) {
     out.append("Mappings:\n");
     for (Range r : ranges) {
       String js = javascript.substring(r.getStart(), r.getEnd());
-      out.append(js);
+      out.append(escape(js));
       out.append("\n");
     }
     return out.toString();
   }
+
+  /**
+   * Escape newlines in a readable way so that each range is on one line for comparison.
+   */
+  private String escape(String js) {
+    return js.replace("\\n", "\\\\n").replace("\n", "\\n");
+  }
 }