Add dev script to make tracing easier.

This creates a `./dev` folder (for stashing helpful development
scripts/utils/etc).

The specific file added here (`dev/trace-multiple-visit.js') can be used
for quickly tracing the characteristics of the following:

* `require('fastboot')` - Labeled in the trace as `"require fastboot"`
* `new FastBoot({ distPath: '...' })` - Labeled in the trace as
  `"initial setup"`
* `await fastboot.visit('/')` - Labeled in the trace as `"first visit"`
* `await fastboot.visit('/')` - Labeled in the trace as `"second visit"`
* `await fastboot.visit('/')` - Labeled in the trace as `"third visit"`

General usage and evaluation steps:

1. run the script (e.g. `node dev/trace-multiple-visit.js`)
2. Navigate Chrome to the `chrome:tracing`
3. Click "load" (in the top left) and navigate to this repo, select the `node_trace.1.log` file
4. Review / evaluate

Co-authored-by: Kris Selden <[email protected]>

Author: Robert Jackson

.eslintrc.js

@@ -12,4 +12,20 @@ module.exports = {
   rules: {
     'no-console': ['error', { allow: ['warn', 'error'] }],
   },
+  overrides: [
+    // override eslint in the dev/* folder to allow features from more recent
+    // Node versions
+    {
+      files: ['dev/**/*.js'],
+      rules: {
+        'node/no-unsupported-features/node-builtins': [
+          'error',
+          {
+            version: '>=10.0.0',
+            ignores: [],
+          },
+        ],
+      },
+    },
+  ],
 };

dev/trace-multiple-visit.js

@@ -0,0 +1,66 @@
+'use strict';
+
+/**
+ * This script is used for quickly tracing the characteristics of the following:
+ *
+ * - `require('fastboot')` - Labeled in the trace as `"require fastboot"`
+ * - `new FastBoot({ distPath: '...' })` - Labeled in the trace as `"initial setup"`
+ * - `await fastboot.visit('/')` - Labeled in the trace as `"first visit"`
+ * - `await fastboot.visit('/')` - Labeled in the trace as `"second visit"`
+ * - `await fastboot.visit('/')` - Labeled in the trace as `"third visit"`
+ *
+ * General usage and evaluation steps:
+ *
+ * 1. run the script (e.g. `node dev/trace-multiple-visit.js`)
+ * 2. Navigate Chrome to the `chrome:tracing`
+ * 3. Click "load" (in the top left) and navigate to this repo, select the `node_trace.1.log` file
+ * 4. Review / evaluate
+ */
+const path = require('path');
+const { performance } = require('perf_hooks');
+
+// can also enable these via `node --trace-event-categories`
+// enabling here via the JS API to make invocation and testing
+// of this script a bit easier
+/* eslint-disable node/no-missing-require */
+const trace_events = require('trace_events');
+const tracing = trace_events.createTracing({
+  categories: ['v8', 'node.perf', 'node.console', 'node.vm.script'],
+});
+
+async function main() {
+  tracing.enable();
+
+  performance.mark('require fastboot start');
+  const FastBoot = require('../src/index');
+  performance.mark('require fastboot end');
+  performance.measure('require fastboot', 'require fastboot start', 'require fastboot end');
+
+  const distPath = path.join(__dirname, '../test/fixtures/basic-app');
+  performance.mark('setup start');
+  const fastboot = new FastBoot({
+    distPath,
+  });
+  performance.mark('setup end');
+  performance.measure('initial setup', 'setup start', 'setup end');
+
+  performance.mark('visit start');
+  let result = await fastboot.visit('/');
+  await result.html();
+  performance.mark('visit end');
+  performance.measure('first visit', 'visit start', 'visit end');
+
+  performance.mark('visit start');
+  result = await fastboot.visit('/');
+  await result.html();
+  performance.mark('visit end');
+  performance.measure('second visit', 'visit start', 'visit end');
+
+  performance.mark('visit start');
+  result = await fastboot.visit('/');
+  await result.html();
+  performance.mark('visit end');
+  performance.measure('third visit', 'visit start', 'visit end');
+}
+
+main();