refactor(gatsby-source-filesystem): Upgrade XState (#17192)

* Upgrade XState and refactor its usage in gatsby-source-filesystem

* test: add basic test suite for sourceNodes

packages/gatsby-source-filesystem/package.json

@@ -21,7 +21,7 @@
     "progress": "^2.0.3",
     "read-chunk": "^3.2.0",
     "valid-url": "^1.0.9",
-    "xstate": "^3.3.3"
+    "xstate": "^4.6.7"
   },
   "devDependencies": {
     "@babel/cli": "^7.5.5",

packages/gatsby-source-filesystem/src/__tests__/gatsby-node.js

@@ -0,0 +1,274 @@
+const mockFS = {
+  existsSync: jest.fn(() => true),
+}
+
+jest.mock(`fs`, () => mockFS)
+jest.mock(`fs-extra`, () => mockFS)
+
+jest.mock(`path`, () => {
+  return {
+    isAbsolute: jest.fn(() => true),
+  }
+})
+
+jest.mock(`../create-file-node`, () => {
+  return {
+    createFileNode: jest.fn(() => Promise.resolve({})),
+  }
+})
+
+jest.mock(`chokidar`, () => {
+  return {
+    watch: jest.fn(),
+  }
+})
+
+const chokidar = require(`chokidar`)
+const { createFileNode } = require(`../create-file-node`)
+
+const mitt = require(`mitt`)
+
+const gatsbyNode = require(`../gatsby-node`)
+
+const createApi = () => {
+  return {
+    actions: {
+      createTypes: jest.fn(),
+      createNode: jest.fn(),
+      deleteNode: jest.fn(),
+    },
+    emitter: mitt(),
+    createNodeId: jest.fn(),
+    getNode: jest.fn(() => {
+      // return truthy
+      return {}
+    }),
+  }
+}
+
+const tick = () => new Promise(resolve => setTimeout(resolve, 0))
+
+describe(`tests`, () => {
+  let on
+
+  const emitChokidarEvent = async (eventType, ...args) => {
+    const listenerSet = on.get(eventType)
+    if (!listenerSet) {
+      return
+    }
+
+    listenerSet.forEach(listener => {
+      listener(...args)
+    })
+    await tick()
+  }
+
+  beforeEach(() => {
+    on = new Map()
+    chokidar.watch.mockImplementation(() => {
+      const mock = {
+        on: (eventType, listener) => {
+          if (!on.has(eventType)) {
+            on.set(eventType, new Set())
+          }
+          const listenerSet = on.get(eventType)
+          listenerSet.add(listener)
+        },
+      }
+      return mock
+    })
+    createFileNode.mockClear()
+  })
+
+  describe(`handles chokidar events emitted before "ready"`, () => {
+    it(`queues node creation from added files`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      await emitChokidarEvent(`add`, `test.md`)
+
+      // ready was not emitted, so no nodes should be created
+      expect(createFileNode).not.toBeCalled()
+      expect(api.actions.createNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      expect(api.actions.createNode).toBeCalled()
+    })
+
+    // change event doesn't queue currently - this need to be fixed
+    it.skip(`queues node creation from changed files`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      await emitChokidarEvent(`change`, `test.md`)
+      // ready was not emitted, so no nodes should be created
+      expect(createFileNode).not.toBeCalled()
+      expect(api.actions.createNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      expect(api.actions.createNode).toBeCalled()
+    })
+
+    it(`queues node creation from added directories`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      await emitChokidarEvent(`addDir`, `test`)
+
+      // ready was not emitted, so no nodes should be created
+      expect(createFileNode).not.toBeCalled()
+      expect(api.actions.createNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      expect(api.actions.createNode).toBeCalled()
+    })
+
+    // unlink event doesn't queue currently - this need to be fixed
+    it.skip(`queues node deletion from deleted files`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      await emitChokidarEvent(`unlink`, `test.md`)
+
+      // ready was not emitted, so no nodes should be deleted
+      expect(api.actions.deleteNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      expect(api.actions.deleteNode).toBeCalled()
+    })
+
+    // unlinkDir event doesn't queue currently - this need to be fixed
+    it.skip(`queues node deletion from deleted directories`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      await emitChokidarEvent(`unlinkDir`, `test`)
+
+      // ready was not emitted, so no nodes should be deleted
+      expect(api.actions.deleteNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      expect(api.actions.deleteNode).toBeCalled()
+    })
+  })
+
+  describe(`handles chokidar events emitted after "ready"`, () => {
+    it(`creates nodes from added files`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      // ready was not emitted, so no nodes should be created
+      expect(createFileNode).not.toBeCalled()
+      expect(api.actions.createNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      await emitChokidarEvent(`add`, `test.md`)
+
+      expect(api.actions.createNode).toBeCalled()
+    })
+
+    it(`creates nodes from changed files`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      // ready was not emitted, so no nodes should be created
+      expect(createFileNode).not.toBeCalled()
+      expect(api.actions.createNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      await emitChokidarEvent(`change`, `test.md`)
+
+      expect(api.actions.createNode).toBeCalled()
+    })
+
+    it(`creates nodes from added directories`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      // ready was not emitted, so no nodes should be created
+      expect(createFileNode).not.toBeCalled()
+      expect(api.actions.createNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      await emitChokidarEvent(`addDir`, `test`)
+
+      expect(api.actions.createNode).toBeCalled()
+    })
+
+    it(`delete nodes from deleted files`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      // ready was not emitted, so no nodes should be deleted
+      expect(api.actions.deleteNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      await emitChokidarEvent(`unlink`, `test.md`)
+
+      expect(api.actions.deleteNode).toBeCalled()
+    })
+
+    it(`delete nodes from deleted directories`, async () => {
+      const api = createApi()
+      const sourceNodesPromise = gatsbyNode.sourceNodes(api, { path: `` })
+      // allow microtasks execution
+      await tick()
+
+      // ready was not emitted, so no nodes should be deleted
+      expect(api.actions.deleteNode).not.toBeCalled()
+
+      await emitChokidarEvent(`ready`)
+
+      await expect(sourceNodesPromise).resolves.toBeDefined()
+
+      await emitChokidarEvent(`unlinkDir`, `test`)
+
+      expect(api.actions.deleteNode).toBeCalled()
+    })
+  })
+})