flow like the river

BACK_BACK/node_modules/@parcel/watcher/test/errorHandling.js

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+const Watcher = require('../index');
+const fs = require('@parcel/fs');
+const path = require('path');
+const assert = require('assert');
+const {sleep} = require('@parcel/test-utils');
+
+describe('error handling', function() {
+  let tmpFolder = path.join(__dirname, './tmp/');
+
+  before(() => {
+    fs.mkdirp(tmpFolder);
+  });
+
+  it('Should restart child process if it dies', async () => {
+    let watcher = new Watcher({});
+
+    let filepath = path.join(tmpFolder, 'file1.txt');
+
+    await fs.writeFile(filepath, 'this is a text document');
+
+    watcher.add(filepath);
+
+    let changed = false;
+    watcher.once('change', () => {
+      changed = true;
+    });
+
+    if (!watcher.ready) {
+      await new Promise(resolve => watcher.once('ready', resolve));
+    }
+
+    await sleep(250);
+
+    watcher._emulateChildDead();
+
+    await sleep(1000);
+
+    await fs.writeFile(filepath, 'this is not a text document');
+
+    await sleep(500);
+
+    assert(changed, 'Should have emitted a change event.');
+
+    await watcher.stop();
+  });
+
+  it('Should restart child process on errors', async () => {
+    let watcher = new Watcher({});
+
+    let filepath = path.join(tmpFolder, 'file1.txt');
+
+    await fs.writeFile(filepath, 'this is a text document');
+
+    watcher.add(filepath);
+
+    let hasThrown = false;
+    watcher.on('watcherError', () => (hasThrown = true));
+
+    let changed = false;
+    watcher.once('change', () => {
+      changed = true;
+    });
+
+    if (!watcher.ready) {
+      await new Promise(resolve => watcher.once('ready', resolve));
+    }
+
+    await sleep(250);
+
+    watcher._emulateChildError();
+
+    await sleep(1000);
+
+    await fs.writeFile(filepath, 'this is not a text document');
+
+    await sleep(500);
+
+    assert(changed, 'Should have emitted a change event.');
+
+    await watcher.stop();
+
+    assert(hasThrown, 'Should have emitted an error event.');
+  });
+});