esbuild-wasm-bundler/mod.ts

import * as ESBuild from "https://deno.land/x/esbuild@v0.19.2/wasm.js";
import * as Mapper from "https://esm.sh/esbuild-plugin-importmaps@1.0.0"; // https://github.com/andstellar/esbuild-plugin-importmaps

export const Root = new URL(`file://${Deno.cwd().replaceAll("\\", "/")}`).toString()+"/";
console.log("running at", Root);
const resolvePlugin:ESBuild.Plugin = {
  name: "resolve-plugin",
  setup(build) {
    build.onResolve({ filter: /^\.\/.*$/ }, args => {
      console.log("RESOLVE")
      console.log("in:", args)
      const path = new URL(args.path, Root).pathname
      const output = {
        path,
        namespace: 'file',
      };
      console.log("out:", output)
      return output;
    });

    build.onLoad({ filter: /.*/, namespace:"file" }, async (args) => {
      console.log("LOAD")
      console.log(args)
      let contents;
      try
      {
        const result = await fetch("file://"+args.path);
        contents = await result.text();
      }
      catch(e)
      {
        console.log("deno fs access error:", e)
      }
      
      return {
        contents,
        loader: args.path.endsWith('.tsx') ? 'tsx' : 'default',
      };
    });
  },
};

type ImportMap = Parameters<typeof Mapper.importmapPlugin>[0];

  await ESBuild.initialize({ worker: false });
  const result = await ESBuild.build({
    entryPoints: ["./app.tsx"],
    bundle: true,
    minify: true,
    format: "esm",
    jsx: "automatic",
    jsxImportSource: "react",
    plugins:[
      resolvePlugin,
      Mapper.importmapPlugin({
        imports:{"react":"https://esm.sh/preact@10.22.0/compat"}
      }) as ESBuild.Plugin
    ]
  });
  ESBuild.stop();

for(const item of result.outputFiles)
{
  console.log(item.text)
}