gatsby-performance-budget/src/start.js

A package to check performance budget against the page weight of every page

const { fork } = require("child_process");
const path = require("path");

const { getPages, getReport } = require("./helpers.js");

const budgetPath = path.join(process.cwd(), "/budget.js");
const budget = require(budgetPath);

const options = {
  chromeFlags: ["--headless"],
  throttlingMethod: "devtools",
  onlyCategories: ["performance"]
};

const config = {
  extends: "lighthouse:default",
  settings: {
    budgets: budget
  }
};

exports.start = async () => {
  const bin = "node_modules/.bin/gatsby";
  const gatsby = path.join(process.cwd(), bin);

  const buildProcess = await fork(gatsby, ["build"]);

  buildProcess.on("exit", async () => {
    try {
      const serveProcess = await fork(gatsby, ["serve"]);

      const dir = path.join(process.cwd(), "public");
      const pagesDir = await getPages(dir);
      const slugs = pagesDir.map(i => i.replace(dir, ""));

      await getReport(slugs, options, config);

      serveProcess.on("exit", async () => {
        console.log("Production build has been served!");
      });
    } catch (error) {
      console.log(error);
    }
  });
};