Vite Build Watch: Fixing Repeated Analyzer Reports

Hey guys, what's up? Today, we're diving into a pretty specific but super annoying issue that some of you might have run into when working with Vite and the vite-bundle-analyzer plugin. You know that awesome vite build --watch command? It's a lifesaver for development, letting you see your bundle analysis as you tweak your code. But, if you've set your analyzerMode to "static", you might have noticed something weird happening: the analyzer report keeps popping up again and again every time you save a file. It’s like, “Okay, I saw it the first time, thanks!” But nope, it keeps coming back, cluttering your workflow. This article is all about understanding why this happens and, more importantly, how to fix it so you can get back to a smooth development experience. We'll break down the problem, look at the expected behavior, and walk you through the steps to get this sorted. So, buckle up, and let's get this analyzer under control!

The Problem: The Never-Ending Analyzer Loop

So, let's talk about the core issue here. You're happily coding away, using vite build --watch to keep an eye on your bundle size with vite-bundle-analyzer. You've configured it with analyzerMode: "static" and openAnalyzer: true, which is pretty standard for getting a static HTML report to inspect. The problem kicks in when you make a change to a file and save it. Instead of just updating the report or doing nothing if there are no significant changes, the entire analyzer process re-runs, and because openAnalyzer: true is set, it tries to open a new instance of the report in your browser (or a new tab). If you save that file multiple times, which is super common during development, you'll end up with a browser tab graveyard filled with identical bundle analyzer reports. It's not just a minor inconvenience; it can really slow down your workflow, especially if your build process takes a bit of time. You're left clicking around, closing duplicate tabs, and generally feeling like your tools are working against you. This isn't the intended behavior, and it definitely breaks the flow of a productive coding session. The goal is to have the analyzer provide useful insights without becoming a nuisance, and this repeated opening definitely crosses that line. We want the build to watch, but not to obsessively re-open things.

Expected Behavior: A Single, Clear Analysis

What we want, and what makes logical sense, is for the vite build --watch command, when used with analyzerMode: "static", to generate the bundle analysis report once per build cycle, or perhaps only when significant changes necessitate a re-evaluation. When openAnalyzer: true is set, it should open that single report. If you make subsequent changes and the build watcher picks them up, it should ideally update the existing static report file, but not re-open it in the browser every single time. Or, at the very least, it should only open the analyzer if the build process actually resulted in a different output or if it's the first time the build has completed since the watch started. The idea is to get the information you need without constant interruptions. Imagine you're refactoring a component. You save, the watcher kicks in, the bundle is rebuilt, and the analyzer could update its file. But forcing a new browser tab to open every single time you hit save? That's overkill. We're looking for a clean, single instance of the analysis to be available, and for the openAnalyzer flag to trigger that opening behavior judiciously, not aggressively. This makes the developer experience much smoother and less distracting. The analysis is a tool to help you understand your bundle, not a pop-up ad for your own code!

Reproducing the Issue: Step-by-Step

Alright, let's get our hands dirty and see exactly how this bug happens. It's pretty straightforward, and the provided reproduce.zip file and the vite.config.ts snippet make it easy to set up. First things first, you'll need a Vite project. If you don't have one handy, you can create a basic React one using npm create vite@latest my-app --template react and then cd my-app and npm install. Once you have your project set up, you need to install the vite-bundle-analyzer plugin. Go ahead and run: npm install --save-dev vite-bundle-analyzer. Now, let's configure it. You'll need to modify your vite.config.ts file. Replace its contents with the following code:

import { defineConfig } from "vite";
import react from "@vitejs/plugin-react";
import viteBundleAnalyzer from "vite-bundle-analyzer";

// https://vite.dev/config/
export default defineConfig({
  plugins: [
    react(),
    viteBundleAnalyzer({
      analyzerMode: "static",
      openAnalyzer: true,
    }),
  ],
});

See that analyzerMode: "static" and openAnalyzer: true? That's the key combo causing our headache. Now, the final step is to run Vite in watch mode. Open your terminal in your project directory and execute: npm run build -- --watch (or yarn build -- --watch if you're using Yarn). If your package.json doesn't have a build script, you might need to use npx vite build --watch directly. Once the build finishes and the analyzer opens its first report, find any JavaScript or TypeScript file in your src directory (or any file that's part of your application's bundle) and simply save it. You don't even need to change anything; just saving it is enough. You'll immediately see a new instance of the analyzer report opening in your browser. Save it again, and bam, another one opens. Repeat this a few times, and you'll have a browser full of identical reports. This clearly demonstrates the issue: the watch mode, coupled with the static analyzer and the auto-open flag, triggers repeated openings instead of a single, managed display. It’s a repeatable bug, folks!

The Root Cause: How Vite's Watcher and Plugins Interact

So, why does this happen? It all boils down to how Vite's build --watch mode interacts with plugins, specifically vite-bundle-analyzer when configured for static output. When you run vite build --watch, Vite sets up a file watcher. Any time a file changes, Vite's internal mechanism triggers a rebuild. Now, vite-bundle-analyzer is a Vite plugin. Plugins hook into different stages of the build process. In this case, when the build is complete (or potentially during the build if configured to do so), the vite-bundle-analyzer plugin runs its logic. Because analyzerMode is set to "static", it generates an HTML file containing the bundle analysis. Crucially, the openAnalyzer: true option tells the plugin,