React Fiber Reconciler (#6690)

This is an outline for the new reconciler infrastructure.

I created a noop renderer to have something to get started from.

I split the reconciler folder into old and new, as well as shared.
I put shouldUpdateReactComponent in shared as an example of a
utility that can easily be shared between both. I plan on breaking
out more utilities like these.
(cherry picked from commit cf157886e9)

src/renderers/noop/ReactNoop.js

@@ -0,0 +1,84 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactNoop
+ * @flow
+ */
+
+/**
+ * This is a renderer of React that doesn't have a render target output.
+ * It is useful to demonstrate the internals of the reconciler in isolation
+ * and for testing semantics of reconciliation separate from the host
+ * environment.
+ */
+
+'use strict';
+
+var ReactFiberReconciler = require('ReactFiberReconciler');
+
+var scheduledHighPriCallback = null;
+var scheduledLowPriCallback = null;
+
+var NoopRenderer = ReactFiberReconciler({
+
+  createHostInstance() {
+
+  },
+  scheduleHighPriCallback(callback) {
+    scheduledHighPriCallback = callback;
+  },
+  scheduleLowPriCallback(callback) {
+    scheduledLowPriCallback = callback;
+  },
+
+});
+
+var ReactNoop = {
+
+  render(element : ReactElement) {
+
+    NoopRenderer.mountNewRoot(element);
+
+  },
+
+  flushHighPri() {
+    var cb = scheduledHighPriCallback;
+    if (cb === null) {
+      return;
+    }
+    scheduledHighPriCallback = null;
+    cb();
+  },
+
+  flushLowPri(timeout : number = Infinity) {
+    var cb = scheduledLowPriCallback;
+    if (cb === null) {
+      return;
+    }
+    scheduledLowPriCallback = null;
+    var timeRemaining = timeout;
+    cb({
+      timeRemaining() {
+        // Simulate a fix amount of time progressing between each call.
+        timeRemaining -= 5;
+        if (timeRemaining < 0) {
+          timeRemaining = 0;
+        }
+        return timeRemaining;
+      },
+    });
+  },
+
+  flush() {
+    ReactNoop.flushHighPri();
+    ReactNoop.flushLowPri();
+  },
+
+};
+
+module.exports = ReactNoop;

src/renderers/noop/__tests__/ReactNoop-test.js

@@ -0,0 +1,57 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @emails react-core
+ */
+
+'use strict';
+
+var React;
+var ReactNoop;
+
+describe('ReactComponent', function() {
+  beforeEach(function() {
+    React = require('React');
+    ReactNoop = require('ReactNoop');
+  });
+
+  it('should render a simple component', function() {
+
+    function Bar() {
+      return <div>Hello World</div>;
+    }
+
+    function Foo() {
+      return <Bar isBar={true} />;
+    }
+
+    ReactNoop.render(<Foo />);
+    ReactNoop.flush();
+
+  });
+
+  it('should render a simple component, in steps if needed', function() {
+
+    function Bar() {
+      return <div>Hello World</div>;
+    }
+
+    function Foo() {
+      return <Bar isBar={true} />;
+    }
+
+    ReactNoop.render(<Foo />);
+    // console.log('Nothing done');
+    ReactNoop.flushLowPri(7);
+    // console.log('Yield');
+    ReactNoop.flushLowPri(50);
+    // console.log('Done');
+  });
+
+
+});

src/renderers/shared/fiber/ReactFiber.js

@@ -0,0 +1,59 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactFiber
+ * @flow
+ */
+
+'use strict';
+
+type StateNode = {};
+type EffectHandler = () => void;
+type EffectTag = number;
+
+export type Fiber = {
+
+  tag: number,
+
+  parent: ?Fiber,
+  child: ?Fiber,
+  sibling: ?Fiber,
+
+  input: ?Object,
+  output: ?Object,
+
+  handler: EffectHandler,
+  handlerTag: EffectTag,
+
+  hasPendingChanges: bool,
+
+  stateNode: StateNode,
+
+};
+
+module.exports = function(tag : number) : Fiber {
+  return {
+
+    tag: tag,
+
+    parent: null,
+    child: null,
+    sibling: null,
+
+    input: null,
+    output: null,
+
+    handler: function() {},
+    handlerTag: 0,
+
+    hasPendingChanges: true,
+
+    stateNode: {},
+
+  };
+};

src/renderers/shared/fiber/ReactFiberFunctionalComponent.js

@@ -0,0 +1,45 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactFiberFunctionalComponent
+ * @flow
+ */
+
+'use strict';
+
+import type { Fiber } from 'ReactFiber';
+var createFiber = require('ReactFiber');
+
+var ReactTypesOfWork = require('ReactTypesOfWork');
+var {
+  FunctionalComponent,
+} = ReactTypesOfWork;
+
+exports.performWork = function(unitOfWork : Fiber) : ?Fiber {
+  var element = unitOfWork.input;
+  if (!element) {
+    throw new Error('Should be resolved by now');
+  }
+  var fn = element.type;
+  var props = element.props;
+  // console.log('perform work on:', fn.name);
+  var nextElement = fn(props);
+
+  if (typeof nextElement.type === 'function') {
+    return exports.createFiber(nextElement);
+  }
+  return null;
+};
+
+exports.createFiber = function(element : ReactElement) {
+  var fiber = createFiber(
+    FunctionalComponent
+  );
+  fiber.input = element;
+  return fiber;
+};

src/renderers/shared/fiber/ReactFiberReconciler.js

@@ -0,0 +1,109 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactFiberReconciler
+ * @flow
+ */
+
+'use strict';
+
+import type { Fiber } from 'ReactFiber';
+var ReactFiberFunctionalComponent = require('ReactFiberFunctionalComponent');
+
+var ReactTypesOfWork = require('ReactTypesOfWork');
+var {
+  FunctionalComponent,
+  ClassComponent,
+  NativeComponent,
+} = ReactTypesOfWork;
+
+type ReactHostElement<T, P> = {
+  type: T,
+  props: P
+};
+
+type Deadline = {
+  timeRemaining : () => number
+};
+
+var timeHeuristicForUnitOfWork = 1;
+
+export type HostConfig<T, P, I> = {
+
+  createHostInstance(element : ReactHostElement<T, P>) : I,
+  scheduleHighPriCallback(callback : () => void) : void,
+  scheduleLowPriCallback(callback : (deadline : Deadline) => void) : void
+
+};
+
+type OpaqueID = {};
+
+export type Reconciler = {
+  mountNewRoot(element : ReactElement) : OpaqueID;
+};
+
+module.exports = function<T, P, I>(config : HostConfig<T, P, I>) : Reconciler {
+
+  // const scheduleHighPriCallback = config.scheduleHighPriCallback;
+  const scheduleLowPriCallback = config.scheduleLowPriCallback;
+
+  let nextUnitOfWork : ?Fiber = null;
+
+  function performUnitOfWork(unit : Fiber) : ?Fiber {
+    switch (unit.tag) {
+      case FunctionalComponent:
+        return ReactFiberFunctionalComponent.performWork(unit);
+      case ClassComponent:
+        break;
+      case NativeComponent:
+        break;
+    }
+    return null;
+  }
+
+  function performLowPriWork(deadline : Deadline) {
+    while (nextUnitOfWork) {
+      if (deadline.timeRemaining() > timeHeuristicForUnitOfWork) {
+        nextUnitOfWork = performUnitOfWork(nextUnitOfWork);
+      } else {
+        scheduleLowPriCallback(performLowPriWork);
+        break;
+      }
+    }
+  }
+
+  function ensureLowPriIsScheduled() {
+    if (nextUnitOfWork) {
+      return;
+    }
+    scheduleLowPriCallback(performLowPriWork);
+  }
+
+  /*
+  function performHighPriWork() {
+    // There is no such thing as high pri work yet.
+  }
+
+  function ensureHighPriIsScheduled() {
+    scheduleHighPriCallback(performHighPriWork);
+  }
+  */
+
+  return {
+
+    mountNewRoot(element : ReactElement) : OpaqueID {
+
+      ensureLowPriIsScheduled();
+
+      nextUnitOfWork = ReactFiberFunctionalComponent.createFiber(element);
+
+      return {};
+    },
+
+  };
+};

src/renderers/shared/fiber/ReactStateNode.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactStateNode
+ * @flow
+ */
+
+'use strict';
+
+type StateNode = {
+  next: ?{ [key: string]: StateNode },
+};
+
+module.exports = function() : StateNode {
+  return {
+    next: null,
+  };
+};

src/renderers/shared/fiber/ReactTypesOfWork.js

@@ -0,0 +1,21 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactTypesOfWork
+ * @flow
+ */
+
+'use strict';
+
+var TypesOfWork = {
+  FunctionalComponent: 1,
+  ClassComponent: 2,
+  NativeComponent: 3,
+};
+
+module.exports = TypesOfWork;