Remove the cycle from babel-types/babel-traverse.

packages/babel-traverse/src/index.js

@@ -42,24 +42,7 @@ traverse.Scope    = require("./scope");
 traverse.Hub      = require("./hub");
 
 traverse.cheap = function (node, enter) {
-  if (!node) return;
-
-  let keys = t.VISITOR_KEYS[node.type];
-  if (!keys) return;
-
-  enter(node);
-
-  for (let key of keys) {
-    let subNode = node[key];
-
-    if (Array.isArray(subNode)) {
-      for (let node of subNode) {
-        traverse.cheap(node, enter);
-      }
-    } else {
-      traverse.cheap(subNode, enter);
-    }
-  }
+  return t.traverseFast(node, enter);
 };
 
 traverse.node = function (node: Object, opts: Object, scope: Object, state: Object, parentPath: Object, skipKeys?) {
@@ -73,31 +56,14 @@ traverse.node = function (node: Object, opts: Object, scope: Object, state: Obje
   }
 };
 
-const CLEAR_KEYS: Array = t.COMMENT_KEYS.concat([
-  "tokens", "comments",
-  "start", "end", "loc",
-  "raw", "rawValue"
-]);
-
 traverse.clearNode = function (node) {
-  for (let key of CLEAR_KEYS) {
-    if (node[key] != null) node[key] = undefined;
-  }
-
-  for (let key in node) {
-    if (key[0] === "_" && node[key] != null) node[key] = undefined;
-  }
+  t.removeProperties(node);
 
   cache.path.delete(node);
-
-  let syms: Array<Symbol> = Object.getOwnPropertySymbols(node);
-  for (let sym of syms) {
-    node[sym] = null;
-  }
 };
 
 traverse.removeProperties = function (tree) {
-  traverse.cheap(tree, traverse.clearNode);
+  t.traverseFast(tree, traverse.clearNode);
   return tree;
 };
 

packages/babel-types/package.json

@@ -9,7 +9,6 @@
   "main": "lib/index.js",
   "dependencies": {
     "babel-runtime": "^6.9.1",
-    "babel-traverse": "^6.14.0",
     "esutils": "^2.0.2",
     "lodash": "^4.2.0",
     "to-fast-properties": "^1.0.1"

packages/babel-types/src/converters.js

@@ -98,14 +98,7 @@ export function toSequenceExpression(nodes: Array<Object>, scope: Scope): ?Objec
   }
 }
 
-// Can't use import because of cyclic dependency between babel-traverse
-// and this module (babel-types). This require needs to appear after
-// we export the TYPES constant, so we lazy-initialize it before use.
-let traverse;
-
 export function toKeyAlias(node: Object, key: Object = node.key): string {
-  if (!traverse) traverse = require("babel-traverse").default;
-
   let alias;
 
   if (node.kind === "method") {
@@ -115,7 +108,7 @@ export function toKeyAlias(node: Object, key: Object = node.key): string {
   } else if (t.isStringLiteral(key)) {
     alias = JSON.stringify(key.value);
   } else {
-    alias = JSON.stringify(traverse.removeProperties(t.cloneDeep(key)));
+    alias = JSON.stringify(t.removePropertiesDeep(t.cloneDeep(key)));
   }
 
   if (node.computed) {

packages/babel-types/src/index.js

@@ -399,18 +399,11 @@ function _inheritComments(key, child, parent) {
   }
 }
 
-// Can't use import because of cyclic dependency between babel-traverse
-// and this module (babel-types). This require needs to appear after
-// we export the TYPES constant, so we lazy-initialize it before use.
-let traverse;
-
 /**
  * Inherit all contextual properties from `parent` node to `child` node.
  */
 
 export function inherits(child: Object, parent: Object): Object {
-  if (!traverse) traverse = require("babel-traverse").default;
-
   if (!child || !parent) return child;
 
   // optionally inherit specific properties if not null
@@ -431,7 +424,6 @@ export function inherits(child: Object, parent: Object): Object {
   }
 
   t.inheritsComments(child, parent);
-  traverse.copyCache(parent, child);
 
   return child;
 }
@@ -459,6 +451,62 @@ export function isNode(node?): boolean {
 toFastProperties(t);
 toFastProperties(t.VISITOR_KEYS);
 
+/**
+ * A prefix AST traversal implementation implementation.
+ */
+
+export function traverseFast(node: Node, enter: (node: Node) => void) {
+  if (!node) return;
+
+  let keys = t.VISITOR_KEYS[node.type];
+  if (!keys) return;
+
+  enter(node);
+
+  for (let key of keys) {
+    let subNode = node[key];
+
+    if (Array.isArray(subNode)) {
+      for (let node of subNode) {
+        traverseFast(node, enter);
+      }
+    } else {
+      traverseFast(subNode, enter);
+    }
+  }
+}
+
+const CLEAR_KEYS: Array = t.COMMENT_KEYS.concat([
+  "tokens", "comments",
+  "start", "end", "loc",
+  "raw", "rawValue"
+]);
+
+/**
+ * Remove all of the _* properties from a node along with the additional metadata
+ * properties like location data and raw token data.
+ */
+
+export function removeProperties(node: Node): void {
+  for (let key of CLEAR_KEYS) {
+    if (node[key] != null) node[key] = undefined;
+  }
+
+  for (let key in node) {
+    if (key[0] === "_" && node[key] != null) node[key] = undefined;
+  }
+
+  let syms: Array<Symbol> = Object.getOwnPropertySymbols(node);
+  for (let sym of syms) {
+    node[sym] = null;
+  }
+}
+
+export function removePropertiesDeep(tree: Node): Node {
+  traverseFast(tree, removeProperties);
+  return tree;
+}
+
 //
 export {
   getBindingIdentifiers,