During a node traversal, it is known that the "inputId" does not chan…

…ge between the script nodes, avoid a hash lookup every time "getInput" is called by caching it.

Note: the whole concept of InputId<-->Input was created to support the original Dart to JS compiler (DartC) which needed support for multiple inputs with the same original file name.  While this is a useful concept it isn't currently used in any meaningful way and it might be possible to eliminate the whole abstraction.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133675962

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

@@ -76,6 +76,7 @@ public class NodeTraversal {
 
   /** The current input */
   private InputId inputId;
+  private CompilerInput compilerInput;
 
   /** The scope creator */
   private final ScopeCreator scopeCreator;
@@ -281,8 +282,7 @@ public NodeTraversal(AbstractCompiler compiler, Callback cb,
       this.scopeCallback = (ScopedCallback) cb;
     }
     this.compiler = compiler;
-    this.inputId = null;
-    this.sourceName = "";
+    setInputId(null, "");
     this.scopeCreator = scopeCreator;
     this.useBlockScope = scopeCreator.hasBlockScope();
   }
@@ -319,8 +319,7 @@ private String formatNodeContext(String label, Node n) {
    */
   public void traverse(Node root) {
     try {
-      inputId = NodeUtil.getInputId(root);
-      sourceName = "";
+      setInputId(NodeUtil.getInputId(root), "");
       curNode = root;
       pushScope(root);
       // null parent ensures that the shallow callbacks will traverse root
@@ -336,8 +335,7 @@ void traverseRoots(Node externs, Node root) {
       Node scopeRoot = externs.getParent();
       Preconditions.checkNotNull(scopeRoot);
 
-      inputId = NodeUtil.getInputId(scopeRoot);
-      sourceName = "";
+      setInputId(NodeUtil.getInputId(scopeRoot), "");
       curNode = scopeRoot;
       pushScope(scopeRoot);
 
@@ -377,8 +375,7 @@ private String formatNodePosition(Node n) {
   void traverseWithScope(Node root, Scope s) {
     Preconditions.checkState(s.isGlobal());
     try {
-      inputId = null;
-      sourceName = "";
+      setInputId(null, "");
       curNode = root;
       pushScope(s);
       traverseBranch(root, null);
@@ -398,9 +395,8 @@ void traverseAtScope(Scope s) {
       // We need to do some extra magic to make sure that the scope doesn't
       // get re-created when we dive into the function.
       if (inputId == null) {
-        inputId = NodeUtil.getInputId(n);
+        setInputId(NodeUtil.getInputId(n), getSourceName(n));
       }
-      sourceName = getSourceName(n);
       curNode = n;
       pushScope(s);
 
@@ -412,9 +408,8 @@ void traverseAtScope(Scope s) {
       popScope();
     } else if (n.isBlock()) {
       if (inputId == null) {
-        inputId = NodeUtil.getInputId(n);
+        setInputId(NodeUtil.getInputId(n), getSourceName(n));
       }
-      sourceName = getSourceName(n);
       curNode = n;
       pushScope(s);
 
@@ -440,7 +435,7 @@ public void traverseFunctionOutOfBand(Node node, Scope scope) {
     Preconditions.checkState(node.isFunction());
     Preconditions.checkState(scope.getRootNode() != null);
     if (inputId == null) {
-      inputId = NodeUtil.getInputId(node);
+      setInputId(NodeUtil.getInputId(node), getSourceName(node));
     }
     curNode = node.getParent();
     pushScope(scope, true /* quietly */);
@@ -461,7 +456,7 @@ public void traverseFunctionOutOfBand(Node node, Scope scope) {
   void traverseInnerNode(Node node, Node parent, Scope refinedScope) {
     Preconditions.checkNotNull(parent);
     if (inputId == null) {
-      inputId = NodeUtil.getInputId(node);
+      setInputId(NodeUtil.getInputId(node), getSourceName(node));
     }
     if (refinedScope != null && getScope() != refinedScope) {
       curNode = node;
@@ -522,7 +517,10 @@ public String getSourceName() {
    * Gets the current input source.
    */
   public CompilerInput getInput() {
-    return compiler.getInput(inputId);
+    if (compilerInput == null) {
+      compilerInput = compiler.getInput(inputId);
+    }
+    return compilerInput;
   }
 
   /**
@@ -620,8 +618,7 @@ public static void traverseRootsTyped(
   private void traverseBranch(Node n, Node parent) {
     Token type = n.getToken();
     if (type == Token.SCRIPT) {
-      inputId = n.getInputId();
-      sourceName = getSourceName(n);
+      setInputId(n.getInputId(), getSourceName(n));
     }
 
     curNode = n;
@@ -934,6 +931,12 @@ private static String getSourceName(Node n) {
     return nullToEmpty(name);
   }
 
+  private void setInputId(InputId id, String sourceName) {
+    inputId = id;
+    this.sourceName = sourceName;
+    compilerInput = null;
+  }
+
   InputId getInputId() {
     return inputId;
   }