fix: Drop Chokidar initial scan events on stop

  When stopping the Chokidar based local watcher while the initial scan
  of the local synchronization directory is taking place, we should drop
  all buffered events rather than flush them and try to process them.

  First, we don't really have any urgency to do so as these events will
  be generated during the next initial scan (when restarting the watcher
  once again), contrary to events emitted by the filesystem while the
  watcher is already running.

  Second, flushing and processing these events can lead to painful
  consequences if the scan was not complete yet since the initial scan
  step will consider any document not scanned yet as missing and will
  generate deletion events for them.

core/local/chokidar/watcher.js

@@ -269,7 +269,7 @@ class LocalWatcher {
 
     if (!this.watcher) return
 
-    if (force) {
+    if (force || !this.initialScanParams.flushed) {
       // Drop buffered events
       this.buffer.clear()
     } else {
@@ -289,7 +289,7 @@ class LocalWatcher {
     // Stop underlying Chokidar watcher
     await this.watcher.close()
     this.watcher = null
-    // Stop accepting new events
+    // Flush buffer and stop flushes loop
     this.buffer.switchMode('idle')
 
     if (!force) {

test/unit/local/chokidar/watcher.js

@@ -18,8 +18,7 @@ const { ContextDir } = require('../../../support/helpers/context_dir')
 const { onPlatform } = require('../../../support/helpers/platform')
 const pouchHelpers = require('../../../support/helpers/pouch')
 
-// TODO: run on darwin platform instead?
-onPlatform('linux', () => {
+onPlatform('darwin', () => {
   describe('ChokidarWatcher Tests', function () {
     let builders
 
@@ -124,6 +123,78 @@ onPlatform('linux', () => {
       })
     })
 
+    describe('stop', () => {
+      context('when initial scan events have not been flushed yet', () => {
+        beforeEach(async function () {
+          await builders.metafile().path('no-event').upToDate().create()
+
+          this.watcher.initialScanParams = {
+            paths: [],
+            emptyDirRetryCount: 3,
+            resolve: Promise.resolve,
+            flushed: false,
+            done: false
+          }
+          // XXX: fake presence of Chokidar watcher
+          this.watcher.watcher = { close: sinon.stub().resolves() }
+        })
+
+        it('clears the buffer and does not flush any event', async function () {
+          const onFlushSpy = sinon.spy(this.watcher, 'onFlush')
+          try {
+            this.watcher.buffer.push({
+              type: 'addDir',
+              path: __dirname,
+              stats: builders.stats().build()
+            })
+            should(this.watcher.buffer.events).have.length(1)
+
+            await this.watcher.stop()
+
+            should(this.watcher.buffer.events).be.empty()
+            should(onFlushSpy).not.have.been.called()
+          } finally {
+            onFlushSpy.restore()
+          }
+        })
+      })
+
+      context('when intial scan events have already been flushed', () => {
+        beforeEach(async function () {
+          await builders.metafile().path('no-event').upToDate().create()
+
+          this.watcher.initialScanParams = {
+            paths: [],
+            emptyDirRetryCount: 3,
+            resolve: Promise.resolve,
+            flushed: true,
+            done: false
+          }
+          // XXX: fake presence of Chokidar watcher
+          this.watcher.watcher = { close: sinon.stub().resolves() }
+        })
+
+        it('tries to flush buffered events before stopping', async function () {
+          const onFlushSpy = sinon.spy(this.watcher, 'onFlush')
+          try {
+            this.watcher.buffer.push({
+              type: 'addDir',
+              path: __dirname,
+              stats: builders.stats().build()
+            })
+            should(this.watcher.buffer.events).have.length(1)
+
+            await this.watcher.stop()
+
+            should(this.watcher.buffer.events).be.empty()
+            should(onFlushSpy).have.been.calledOnce()
+          } finally {
+            onFlushSpy.restore()
+          }
+        })
+      })
+    })
+
     describe('checksum', () => {
       const relpath = 'foo.txt'
       let abspath