Merge pull request #1781 from airbnb/fix_find_statefulness

 - [Fix] `shallow`: `.parents`: ensure that one `.find` call does not affect another
 - [Fix] Freeze ROOT_NODES for child wrappers

Author: ljharb

packages/enzyme-test-suite/test/ReactWrapper-spec.jsx

@@ -3893,6 +3893,53 @@ describeWithDOM('mount', () => {
       const formUp = input.parents('form');
       expect(formUp).to.have.lengthOf(1);
     });
+
+    it('works when called sequentially on two sibling nodes', () => {
+      class Test extends React.Component {
+        render() {
+          return (
+            <div>
+              <div className="a">
+                <div>A child</div>
+              </div>
+              <div className="b">
+                <div>B child</div>
+              </div>
+            </div>
+          );
+        }
+      }
+
+      const wrapper = mount(<Test />);
+
+      const aChild = wrapper.find({ children: 'A child' });
+      expect(aChild.debug()).to.equal(`<div>
+  A child
+</div>`);
+      expect(aChild).to.have.lengthOf(1);
+
+      const bChild = wrapper.find({ children: 'B child' });
+      expect(bChild.debug()).to.equal(`<div>
+  B child
+</div>`);
+      expect(bChild).to.have.lengthOf(1);
+
+      const bChildParents = bChild.parents('.b');
+      expect(bChildParents.debug()).to.equal(`<div className="b">
+  <div>
+    B child
+  </div>
+</div>`);
+      expect(bChildParents).to.have.lengthOf(1);
+
+      const aChildParents = aChild.parents('.a');
+      expect(aChildParents.debug()).to.equal(`<div className="a">
+  <div>
+    A child
+  </div>
+</div>`);
+      expect(aChildParents).to.have.lengthOf(1);
+    });
   });
 
   describe('.parent()', () => {

packages/enzyme-test-suite/test/ShallowWrapper-spec.jsx

@@ -3556,6 +3556,53 @@ describe('shallow', () => {
       expect(parents.at(0).hasClass('foo')).to.equal(true);
       expect(parents.at(1).hasClass('bax')).to.equal(true);
     });
+
+    it('works when called sequentially on two sibling nodes', () => {
+      class Test extends React.Component {
+        render() {
+          return (
+            <div>
+              <div className="a">
+                <div>A child</div>
+              </div>
+              <div className="b">
+                <div>B child</div>
+              </div>
+            </div>
+          );
+        }
+      }
+
+      const wrapper = shallow(<Test />);
+
+      const aChild = wrapper.find({ children: 'A child' });
+      expect(aChild.debug()).to.equal(`<div>
+  A child
+</div>`);
+      expect(aChild).to.have.lengthOf(1);
+
+      const bChild = wrapper.find({ children: 'B child' });
+      expect(bChild.debug()).to.equal(`<div>
+  B child
+</div>`);
+      expect(bChild).to.have.lengthOf(1);
+
+      const bChildParents = bChild.parents('.b');
+      expect(bChildParents.debug()).to.equal(`<div className="b">
+  <div>
+    B child
+  </div>
+</div>`);
+      expect(bChildParents).to.have.lengthOf(1);
+
+      const aChildParents = aChild.parents('.a');
+      expect(aChildParents.debug()).to.equal(`<div className="a">
+  <div>
+    A child
+  </div>
+</div>`);
+      expect(aChildParents).to.have.lengthOf(1);
+    });
   });
 
   describe('.parent()', () => {

packages/enzyme/src/RSTTraversal.js

@@ -106,7 +106,7 @@ export function pathToNode(node, root) {
 }
 
 export function parentsOfNode(node, root) {
-  return pathToNode(node, root).reverse();
+  return (pathToNode(node, root) || []).reverse();
 }
 
 export function nodeHasId(node, id) {

packages/enzyme/src/ReactWrapper.js

@@ -31,6 +31,7 @@ const RENDERER = sym('__renderer__');
 const UNRENDERED = sym('__unrendered__');
 const ROOT = sym('__root__');
 const OPTIONS = sym('__options__');
+const ROOT_NODES = sym('__rootNodes__');
 
 /**
  * Finds all nodes in the current wrapper nodes' render trees that match the provided predicate
@@ -57,8 +58,18 @@ function filterWhereUnwrapped(wrapper, predicate) {
   return wrapper.wrap(wrapper.getNodesInternal().filter(predicate).filter(Boolean));
 }
 
+function getRootNodeInternal(wrapper) {
+  if (wrapper[ROOT].length !== 1) {
+    throw new Error('getRootNodeInternal(wrapper) can only be called when wrapper wraps one node');
+  }
+  if (wrapper[ROOT] !== wrapper) {
+    return wrapper[ROOT_NODES][0];
+  }
+  return wrapper[ROOT][NODE];
+}
+
 function nodeParents(wrapper, node) {
-  return parentsOfNode(node, wrapper[ROOT].getNodeInternal());
+  return parentsOfNode(node, getRootNodeInternal(wrapper));
 }
 
 function privateSetNodes(wrapper, nodes) {
@@ -102,6 +113,7 @@ class ReactWrapper {
       privateSet(this, RENDERER, root[RENDERER]);
       privateSet(this, ROOT, root);
       privateSetNodes(this, nodes);
+      privateSet(this, ROOT_NODES, root[NODES]);
     }
     privateSet(this, OPTIONS, root ? root[OPTIONS] : options);
   }
@@ -639,7 +651,7 @@ class ReactWrapper {
         throw new TypeError('your adapter does not support `simulateError`. Try upgrading it!');
       }
 
-      const rootNode = this[ROOT].getNodeInternal();
+      const rootNode = getRootNodeInternal(this);
       const nodeHierarchy = [thisNode].concat(nodeParents(this, thisNode));
       renderer.simulateError(nodeHierarchy, rootNode, error);
 
@@ -737,8 +749,10 @@ class ReactWrapper {
    * @returns {ReactWrapper}
    */
   parents(selector) {
-    const allParents = this.wrap(this.single('parents', n => nodeParents(this, n)));
-    return selector ? allParents.filter(selector) : allParents;
+    return this.single('parents', (n) => {
+      const allParents = this.wrap(nodeParents(this, n));
+      return selector ? allParents.filter(selector) : allParents;
+    });
   }
 
   /**

packages/enzyme/src/ShallowWrapper.js

@@ -37,6 +37,8 @@ const UNRENDERED = sym('__unrendered__');
 const ROOT = sym('__root__');
 const OPTIONS = sym('__options__');
 const SET_STATE = sym('__setState__');
+const ROOT_NODES = sym('__rootNodes__');
+
 /**
  * Finds all nodes in the current wrapper nodes' render trees that match the provided predicate
  * function.
@@ -144,6 +146,12 @@ function getRootNode(node) {
 }
 
 function getRootNodeInternal(wrapper) {
+  if (wrapper[ROOT].length !== 1) {
+    throw new Error('getRootNodeInternal(wrapper) can only be called when wrapper wraps one node');
+  }
+  if (wrapper[ROOT] !== wrapper) {
+    return wrapper[ROOT_NODES][0];
+  }
   return wrapper[ROOT][NODE];
 }
 
@@ -219,6 +227,7 @@ class ShallowWrapper {
       privateSet(this, RENDERER, root[RENDERER]);
       privateSetNodes(this, nodes);
       privateSet(this, OPTIONS, root[OPTIONS]);
+      privateSet(this, ROOT_NODES, root[NODES]);
     }
   }
 
@@ -972,8 +981,10 @@ class ShallowWrapper {
    * @returns {ShallowWrapper}
    */
   parents(selector) {
-    const allParents = this.wrap(this.single('parents', n => nodeParents(this, n)));
-    return selector ? allParents.filter(selector) : allParents;
+    return this.single('parents', (n) => {
+      const allParents = this.wrap(nodeParents(this, n));
+      return selector ? allParents.filter(selector) : allParents;
+    });
   }
 
   /**