A Vite plugin that introduces a "scan" pre-pass with composition support with user-provided `builder.buildApp`.

scan-pass.ts

import { walk } from "estree-walker";
import * as Vite from "vite";

export default function scanPass(): Vite.PluginOption {
	let buildMode: "build" | "scan" = "build";

	return [
		{
			name: "scan-pass",
			enforce: "post",
			sharedDuringBuild: true,
			config(userConfig) {
				const logger = Vite.createLogger("info");
				return {
					builder: {
						sharedConfigBuild: true,
						async buildApp(builder) {
							builder.config.logger.info("Scanning for imports...");
							buildMode = "scan";

							for (const env of Object.values(builder.environments)) {
								env.config.build.write = false;
							}

							if (userConfig.builder?.buildApp) {
								await userConfig.builder.buildApp(builder);
							} else {
								await builder.buildApp();
							}

							buildMode = "build";
							builder.config.logger.info("Building app...");

							for (const env of Object.values(builder.environments)) {
								env.config.build.write = true;
							}

							if (userConfig.builder?.buildApp) {
								await userConfig.builder.buildApp(builder);
							} else {
								await builder.buildApp();
							}
						},
					},
					customLogger: new Proxy(logger, {
						get(t, p) {
							if (buildMode === "scan" && p !== "error") {
								return () => {};
							}
							return t[p];
						},
					}),
				};
			},
		},
		{
			name: "scan-pass:transform",
			transform(code, id) {
				if (buildMode !== "scan") return;

				const ast = this.parse(code);

				let result = "";
				walk(ast, {
					enter(node) {
						const location = node as unknown as { start: number; end: number };
						switch (node.type) {
							case "ImportDeclaration":
								result += `${code.slice(location.start, location.end)}\n`;
								break;
						}
					},
				});

				return `${result}\nmodule.exports = {};`;
			},
		},
	];
}