Avoid parsing JS files when building a bundle

This avoids the case where LazyParsedDependencyInfo.getLoadFlags() might
parse the entire file to check if a JS file can be bundled as a Closure
or ES6 module.

Fixes #4006

Author: niloc132

src/com/google/javascript/jscomp/AbstractCommandLineRunner.java

@@ -2403,7 +2403,7 @@ void printBundleTo(JSChunk module, Appendable out) throws IOException {
       // ES6 modules will need a runtime in a bundle. Skip appending this runtime if there are no
       // ES6 modules to cut down on size.
       for (CompilerInput input : inputs) {
-        if ("es6".equals(input.getLoadFlags().get("module"))) {
+        if (input.isEs6Module()) {
           appendRuntimeTo(out);
           break;
         }

src/com/google/javascript/jscomp/Compiler.java

@@ -2232,7 +2232,7 @@ private List<CompilerInput> parsePotentialModules(Iterable<CompilerInput> inputs
       // Only process files that are detected as ES6 modules
       if (!options.getDependencyOptions().shouldPrune()
           || !JsFileRegexParser.isSupported()
-          || "es6".equals(input.getLoadFlags().get("module"))) {
+          || input.isEs6Module()) {
         filteredInputs.add(input);
       }
     }

src/com/google/javascript/jscomp/CompilerInput.java

@@ -571,6 +571,16 @@ public String toString() {
     return getName();
   }
 
+  @Override
+  public boolean isEs6Module() {
+    return getDependencyInfo().isEs6Module();
+  }
+
+  @Override
+  public boolean isGoogModule() {
+    return getDependencyInfo().isGoogModule();
+  }
+
   @Override
   public ImmutableMap<String, String> getLoadFlags() {
     return getDependencyInfo().getLoadFlags();

src/com/google/javascript/jscomp/LazyParsedDependencyInfo.java

@@ -43,6 +43,18 @@ public LazyParsedDependencyInfo(DependencyInfo delegate, JsAst ast, AbstractComp
     this.compiler = checkNotNull(compiler);
   }
 
+  @Override
+  public boolean isEs6Module() {
+    // Instead of doing a full parse to look this up, just ask the delegate, which at least has this much info
+    return delegate.isEs6Module();
+  }
+
+  @Override
+  public boolean isGoogModule() {
+    // Instead of doing a full parse to look this up, just ask the delegate, which at least has this much info
+    return delegate.isGoogModule();
+  }
+
   @Override
   public ImmutableMap<String, String> getLoadFlags() {
     if (loadFlags == null) {

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

@@ -189,9 +189,9 @@ public void appendTo(Appendable out, DependencyInfo info, File content, Charset
   /** Append the contents of the CharSource to the supplied appendable. */
   public void appendTo(Appendable out, DependencyInfo info, CharSource content) throws IOException {
     String code = content.read();
-    if (info.isModule()) {
+    if (info.isGoogModule()) {
       mode.appendGoogModule(transpile(code), out, sourceUrl);
-    } else if ("es6".equals(info.getLoadFlags().get("module")) && transpiler == Transpiler.NULL) {
+    } else if (info.isEs6Module() && transpiler == Transpiler.NULL) {
       // TODO(johnplaisted): Make the default transpiler the ES_MODULE_TO_CJS_TRANSPILER. Currently
       // some code is passing in unicode identifiers in non-ES6 modules the compiler fails to parse.
       // Once this compiler bug is fixed we can always transpile.

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

@@ -140,6 +140,13 @@ abstract static class Builder {
   /** Whether the symbol is provided by a module */
   boolean isModule();
 
+  default boolean isEs6Module() {
+    return "es6".equals(getLoadFlags().get("module"));
+  }
+  default boolean isGoogModule() {
+    return "goog".equals(getLoadFlags().get("module"));
+  }
+
   /** Whether the file '@externs' annotation. */
   boolean getHasExternsAnnotation();
 
@@ -152,7 +159,7 @@ abstract static class Builder {
    */
   abstract class Base implements DependencyInfo {
     @Override public boolean isModule() {
-      return "goog".equals(getLoadFlags().get("module"));
+      return isGoogModule();
     }
 
     @Override

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

@@ -219,7 +219,7 @@ private Map<String, DependencyInfo> removeMungedSymbols(
 
       ImmutableList<String> provides = dependencyInfo.getProvides();
 
-      if ("es6".equals(dependencyInfo.getLoadFlags().get("module"))) {
+      if (dependencyInfo.isEs6Module()) {
         String mungedProvide = loader.resolve(dependencyInfo.getName()).toModuleName();
         // Filter out the munged symbol.
         // Note that at the moment ES6 modules should not have any other provides! In the future
@@ -278,7 +278,7 @@ private void validateDependencies(Iterable<DependencyInfo> preparsedFileDependen
           reportSameFile(namespace, depInfo);
         } else {
           depInfo.isModule();
-          boolean providerIsEs6Module = "es6".equals(provider.getLoadFlags().get("module"));
+          boolean providerIsEs6Module = provider.isEs6Module();
 
           switch (require.getType()) {
             case ES6_IMPORT:
@@ -363,7 +363,7 @@ private void addToProvideMap(
                 .toModuleName());
       } else {
         // ES6 modules already provide these munged symbols.
-        if (!"es6".equals(depInfo.getLoadFlags().get("module"))) {
+        if (!depInfo.isEs6Module()) {
           provides.add(loader.resolve(depInfo.getName()).toModuleName());
         }
       }

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

@@ -207,7 +207,7 @@ private void processInputs() {
           || (provides.size() == 1
               && firstProvide.startsWith("module$")
               // ES6 modules should always be considered as exporting something.
-              && !"es6".equals(userOrderedInput.getLoadFlags().get("module")))) {
+              && !userOrderedInput.isEs6Module())) {
         nonExportingInputs.put(
             ModuleNames.fileToModuleName(userOrderedInput.getName()), userOrderedInput);
       }