Refactor TranspilingClosureBundler into a ClosureBundler and an encap…

…sulated Transpiler.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=139596773

src/com/google/javascript/jscomp/deps/ClosureBundler.java

@@ -15,27 +15,47 @@
  */
 package com.google.javascript.jscomp.deps;
 
+import com.google.common.base.Strings;
 import com.google.common.io.CharSource;
 import com.google.common.io.Files;
-
+import com.google.javascript.jscomp.transpile.TranspileResult;
+import com.google.javascript.jscomp.transpile.Transpiler;
 import java.io.File;
 import java.io.IOException;
 import java.nio.charset.Charset;
-
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * A utility class to assist in creating JS bundle files.
  */
 public class ClosureBundler {
-  private boolean useEval = false;
+
+  private final Transpiler transpiler;
+
+  private EvalMode mode = EvalMode.NORMAL;
   private String sourceUrl = null;
   private String path = "unknown_source";
 
+  // TODO(sdh): This cache should be moved out into a higher level, but is
+  // currently required due to the API that source maps must be accessible
+  // via just a path (and not the file contents).
+  private final Map<String, String> sourceMapCache = new ConcurrentHashMap<>();
+
+  // TODO(sdh): This causes serious problems with edit-refresh if the bundler
+  // is used in the wrong scope.  The logic must be moved outside this class.
+  private boolean shouldSendRuntime = true;
+
   public ClosureBundler() {
+    this(Transpiler.NULL);
+  }
+
+  public ClosureBundler(Transpiler transpiler) {
+    this.transpiler = transpiler;
   }
 
   public final ClosureBundler useEval(boolean useEval) {
-    this.useEval = useEval;
+    this.mode = useEval ? EvalMode.EVAL : EvalMode.NORMAL;
     return this;
   }
 
@@ -78,10 +98,19 @@ public void appendTo(
       Appendable out,
       DependencyInfo info,
       CharSource content) throws IOException {
+    // TODO(sdh): Move this logic into the bundle manager.
+    if (shouldSendRuntime) {
+      String runtime = transpiler.runtime();
+      if (!runtime.isEmpty()) {
+        mode.appendTraditional(runtime, out, null);
+      }
+      shouldSendRuntime = false;
+    }
+
     if (info.isModule()) {
-      appendGoogModule(out, content);
+      mode.appendGoogModule(transpile(content.read()), out, sourceUrl);
     } else {
-      appendTraditional(out, content);
+      mode.appendTraditional(transpile(content.read()), out, sourceUrl);
     }
   }
 
@@ -90,44 +119,60 @@ public void appendTo(
    * method.
    */
   public String getSourceMap(String path) {
-    return "";
+    return Strings.nullToEmpty(sourceMapCache.get(path));
   }
 
-  private void appendTraditional(Appendable out, CharSource contents)
-      throws IOException {
-    if (useEval) {
-      out.append("(0,eval(\"");
-      append(out, Mode.ESCAPED, contents);
-      appendSourceUrl(out, Mode.ESCAPED);
-      out.append("\"));\n");
-    } else {
-      append(out, Mode.NORMAL, contents);
-      appendSourceUrl(out, Mode.NORMAL);
-    }
+  private String transpile(String s) {
+    TranspileResult result = transpiler.transpile(path, s);
+    sourceMapCache.put(path, result.sourceMap());
+    return result.transpiled();
   }
 
-  private void appendGoogModule(Appendable out, CharSource contents)
-      throws IOException {
-    if (useEval) {
-      out.append("goog.loadModule(\"");
-      append(out, Mode.ESCAPED, contents);
-      appendSourceUrl(out, Mode.ESCAPED);
-      out.append("\");\n");
-    } else {
-      // add the prefix on the first line so the line numbers aren't affected.
-      out.append(
-          "goog.loadModule(function(exports) {"
-          + "'use strict';");
-      append(out, Mode.NORMAL, contents);
-      out.append(
-          "\n" // terminate any trailing single line comment.
-          + ";" // terminate any trailing expression.
-          + "return exports;});\n");
-      appendSourceUrl(out, Mode.NORMAL);
-    }
+  private enum EvalMode {
+    EVAL {
+      @Override
+      void appendTraditional(String s, Appendable out, String sourceUrl) throws IOException {
+        out.append("(0,eval(\"");
+        EscapeMode.ESCAPED.append(s, out);
+        appendSourceUrl(out, EscapeMode.ESCAPED, sourceUrl);
+        out.append("\"));\n");
+      }
+
+      @Override
+      void appendGoogModule(String s, Appendable out, String sourceUrl) throws IOException {
+        out.append("goog.loadModule(\"");
+        EscapeMode.ESCAPED.append(s, out);
+        appendSourceUrl(out, EscapeMode.ESCAPED, sourceUrl);
+        out.append("\");\n");
+      }
+    },
+    NORMAL {
+      @Override
+      void appendTraditional(String s, Appendable out, String sourceUrl) throws IOException {
+        EscapeMode.NORMAL.append(s, out);
+        appendSourceUrl(out, EscapeMode.NORMAL, sourceUrl);
+      }
+
+      @Override
+      void appendGoogModule(String s, Appendable out, String sourceUrl) throws IOException {
+        // add the prefix on the first line so the line numbers aren't affected.
+        out.append(
+            "goog.loadModule(function(exports) {"
+            + "'use strict';");
+        EscapeMode.NORMAL.append(s, out);
+        out.append(
+            "\n" // terminate any trailing single line comment.
+            + ";" // terminate any trailing expression.
+            + "return exports;});\n");
+        appendSourceUrl(out, EscapeMode.NORMAL, sourceUrl);
+      }
+    };
+
+    abstract void appendTraditional(String s, Appendable out, String sourceUrl) throws IOException;
+    abstract void appendGoogModule(String s, Appendable out, String sourceUrl) throws IOException;
   }
 
-  private enum Mode {
+  private enum EscapeMode {
     ESCAPED {
       @Override void append(String s, Appendable out) throws IOException {
         out.append(SourceCodeEscapers.javascriptEscaper().escape(s));
@@ -142,17 +187,8 @@ private enum Mode {
     abstract void append(String s, Appendable out) throws IOException;
   }
 
-  private void append(Appendable out, Mode mode, String s) throws IOException {
-    String transformed = transformInput(s, path);
-    mode.append(transformed, out);
-  }
-
-  private void append(Appendable out, Mode mode, CharSource cs)
+  private static void appendSourceUrl(Appendable out, EscapeMode mode, String sourceUrl)
       throws IOException {
-    append(out, mode, cs.read());
-  }
-
-  private void appendSourceUrl(Appendable out, Mode mode) throws IOException {
     if (sourceUrl == null) {
       return;
     }
@@ -161,13 +197,4 @@ private void appendSourceUrl(Appendable out, Mode mode) throws IOException {
     // but source URLs generally aren't valid JS inputs.
     mode.append(toAppend, out);
   }
-
-  /**
-   * Template method. Subclasses that need to transform the inputs should override this method.
-   * (For example, {@link TranspilingClosureBundler#transformInput} transpiles inputs from ES6
-   * to ES5.)
-   */
-  protected String transformInput(String input, String path) {
-    return input;
-  }
 }