Add path sibling traversal methods (#5230)

* getPrevSibling
* getNextSibling
* getAllNextSiblings
* getAllPrevSiblings

packages/babel-traverse/src/path/family.js

@@ -57,7 +57,7 @@ export function getCompletionRecords(): Array {
   return paths;
 }
 
-export function getSibling(key) {
+export function getSibling(key): NodePath {
   return NodePath.get({
     parentPath: this.parentPath,
     parent: this.parent,
@@ -67,6 +67,36 @@ export function getSibling(key) {
   });
 }
 
+export function getPrevSibling(): NodePath {
+  return this.getSibling(this.key - 1);
+}
+
+export function getNextSibling(): NodePath {
+  return this.getSibling(this.key + 1);
+}
+
+export function getAllNextSiblings(): Array<NodePath> {
+  let _key = this.key;
+  let sibling:NodePath = this.getSibling(++_key);
+  const siblings:Array<NodePath> = [];
+  while (sibling.node) {
+    siblings.push(sibling);
+    sibling = this.getSibling(++_key);
+  }
+  return siblings;
+}
+
+export function getAllPrevSiblings(): Array<NodePath> {
+  let _key = this.key;
+  let sibling:NodePath = this.getSibling(--_key);
+  const siblings:Array<NodePath> = [];
+  while (sibling.node) {
+    siblings.push(sibling);
+    sibling = this.getSibling(--_key);
+  }
+  return siblings;
+}
+
 export function get(key: string, context?: boolean | TraversalContext): NodePath {
   if (context === true) context = this.context;
   const parts = key.split(".");

packages/babel-traverse/test/family.js

@@ -52,6 +52,31 @@ describe("path/family", function () {
         assert.strictEqual(outerNodes[id], outerPaths[id].node, "nodes match");
       });
     });
+
+  });
+  describe("getSibling", function () {
+    const ast = parse("var a = 1, {b} = c, [d] = e; function f() {} function g() {}");
+    let sibling = {}, lastSibling = {};
+    traverse(ast, {
+      VariableDeclaration(path) {
+        sibling = path.getSibling(path.key);
+        lastSibling = sibling.getNextSibling().getNextSibling();
+      }
+    });
+
+    it("should return traverse sibling nodes", function () {
+      assert.ok(sibling.getNextSibling().node, "has property node");
+      assert.ok(lastSibling.getPrevSibling().node, "has property node");
+      assert.equal(!!sibling.getPrevSibling().node, false, "out of scope");
+      assert.equal(!!lastSibling.getNextSibling().node, false, "out of scope");
+    });
+
+    it("should return all preceding and succeeding sibling nodes", function () {
+      assert.ok(sibling.getAllNextSiblings().length, "Has next sibling");
+      assert.ok(lastSibling.getAllPrevSiblings().length, "Has prev sibling");
+      assert.equal(sibling.getAllNextSiblings().length, 2, "Has 2 succeeding sibling");
+      assert.equal(lastSibling.getAllPrevSiblings().length, 2, "Has 2 preceeding sibling");
+    });
   });
 });