optimise named functions depending on whether they contain an assignment/reference - #861

lib/babel/transformation/helpers/name-method.js

@@ -15,11 +15,32 @@ var visitor = {
     if (localDeclar !== state.outerDeclar) return;
 
     state.selfReference = true;
-    this.stop();
+    state.references.push(this);
+
+    if (t.isPattern(parent) || t.isAssignmentExpression(parent) || t.isUpdateExpression(parent)) {
+      state.selfAssignment = true;
+    }
   }
 };
 
-var wrap = function (method, id, scope) {
+var wrapIncludesSelfReference = function (state, method, id, scope) {
+  var outerId = scope.generateUidIdentifier("getOuter");
+  var outerIdCall = t.callExpression(outerId, []);
+
+  for (var i = 0; i < state.references.length; i++) {
+    state.references[i].replaceNode(outerIdCall);
+  }
+
+  method.id = id;
+
+  return util.template("named-function", {
+    GET_OUTER_ID: outerId,
+    FUNCTION_ID:  id,
+    FUNCTION:     method
+  });
+};
+
+var wrapIncludesSelfAssignment = function (state, method, id, scope) {
   var templateName = "property-method-assignment-wrapper";
   if (method.generator) templateName += "-generator";
   return util.template(templateName, {
@@ -30,23 +51,68 @@ var wrap = function (method, id, scope) {
   });
 };
 
+var wrap = function (state, method, id, scope) {
+  if (state.selfReference) {
+    if (state.selfAssignment) {
+      return wrapIncludesSelfAssignment(state, method, id, scope);
+    } else {
+      return wrapIncludesSelfReference(state, method, id, scope);
+    }
+  } else {
+    method.id = id;
+    return method;
+  }
+};
+
 var visit = function (node, name, scope) {
   var state = {
-    name: name,
-    selfReference: false,
-    outerDeclar: scope.getBindingIdentifier(name),
+    selfAssignment: false,
+    selfReference:  false,
+    outerDeclar:    scope.getBindingIdentifier(name),
+    references:     [],
+    name:           name,
   };
 
-  if (doesntHaveLocal(name, scope)) {
+  // check to see if we have a local binding of the id we're setting inside of
+  // the function, this is important as there are caveats associated
+
+  var bindingInfo = scope.getOwnBindingInfo(name);
+
+  if (bindingInfo) {
+    if (bindingInfo.kind === "param") {
+      // safari will blow up in strict mode with code like:
+      //
+      //   var t = function t(t) {};
+      //
+      // with the error:
+      //
+      //   Cannot declare a parameter named 't' as it shadows the name of a
+      //   strict mode function.
+      //
+      // this isn't to the spec and they've invented this behaviour which is
+      // **extremely** annoying so we avoid setting the name if it has a param
+      // with the same id
+      state.selfAssignment = true;
+      state.selfReference = true;
+    } else {
+      // otherwise it's defined somewhere in scope like:
+      //
+      //   var t = function () {
+      //     var t = 2;
+      //   };
+      //
+      // so we can safely just set the id and move along as it shadows the
+      // bound function id
+    }
+  } else {
     scope.traverse(node, visitor, state);
   }
 
   return state;
 };
 
-var doesntHaveLocal = function (name, scope) {
-  var bindingInfo = scope.getOwnBindingInfo(name);
-  return !bindingInfo || bindingInfo.kind !== "param";
+var hasParamOfSameName = function (name, scope) {
+  return bindingInfo && bindingInfo.kind === "param";
 };
 
 exports.property = function (node, file, scope) {
@@ -58,12 +124,7 @@ exports.property = function (node, file, scope) {
 
   var method = node.value;
   var state  = visit(method, name, scope);
-
-  if (state.selfReference) {
-    node.value = wrap(method, id, scope);
-  } else {
-    method.id = id;
-  }
+  node.value = wrap(state, method, id, scope);
 };
 
 exports.bare = function (node, parent, scope) {
@@ -86,13 +147,6 @@ exports.bare = function (node, parent, scope) {
   var name = t.toIdentifier(id.name);
   id = t.identifier(name);
 
-  //
-
   var state = visit(node, name, scope);
-
-  if (state.selfReference) {
-    return wrap(node, id, scope);
-  } else {
-    node.id = id;
-  }
+  return wrap(state, node, id, scope);
 };

lib/babel/transformation/templates/named-func.js

@@ -1,7 +0,0 @@
-(function () {
-    function GET_OUTER_ID() {
-        return ID;
-    }
-
-    return FUNCTION;
-})()

lib/babel/transformation/templates/named-function.js

@@ -0,0 +1,7 @@
+(function () {
+  function GET_OUTER_ID() {
+    return FUNCTION_ID;
+  }
+
+  return FUNCTION;
+})()