ESM support

Author: endel

build.mjs

@@ -0,0 +1,91 @@
+import path from 'path';
+import { fileURLToPath } from 'url';
+import ts from "typescript";
+import esbuild from "esbuild";
+
+// we need to change up how __dirname is used for ES6 purposes
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
+async function main() {
+  // Absolute path to package directory
+  const basePath = __dirname;
+  const target = "es2017";
+
+  // Get all .ts as input files
+  const entryPoints = [
+    path.resolve(basePath, "src", "index.ts").
+      replace(/\\/g, '/') // windows support
+  ];
+
+  const outdir = path.join(basePath, 'build');
+
+  // Emit only .d.ts files
+  const emitTSDeclaration = () => {
+    console.log("Generating .d.ts...");
+    const program = ts.createProgram(entryPoints, {
+      declaration: true,
+      emitDeclarationOnly: true,
+      skipLibCheck: true,
+      module: "commonjs",
+      target,
+      outDir: outdir,
+      esModuleInterop: true,
+      experimentalDecorators: true,
+    });
+    const emitResult = program.emit();
+
+    const allDiagnostics = ts
+      .getPreEmitDiagnostics(program)
+      .concat(emitResult.diagnostics);
+
+    allDiagnostics.forEach(diagnostic => {
+      if (diagnostic.file) {
+        const { line, character } = ts.getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start);
+        const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, "\n");
+        console.log(`${diagnostic.file.fileName} (${line + 1},${character + 1}): ${message}`);
+      } else {
+        console.log(ts.flattenDiagnosticMessageText(diagnostic.messageText, "\n"));
+      }
+    });
+  }
+
+  // CommonJS output
+  console.log("Generating CJS build...");
+  esbuild.build({
+    entryPoints,
+    outdir,
+    target,
+    format: "cjs",
+    target: "es2017",
+    sourcemap: "external",
+    platform: "node",
+  });
+
+  // ESM output
+  console.log("Generating ESM build...");
+  esbuild.build({
+    entryPoints,
+    outdir,
+    target,
+    format: "esm",
+    bundle: true,
+    sourcemap: "external",
+    platform: "node",
+    outExtension: { '.js': '.mjs', },
+    plugins: [{
+      name: 'add-mjs',
+      setup(build) {
+        build.onResolve({ filter: /.*/ }, (args) => {
+          if (args.importer) return { path: args.path.replace(/^\.(.*)\.js$/, '.$1.mjs'), external: true }
+        })
+      },
+    }]
+  });
+
+  // emit .d.ts files
+  emitTSDeclaration();
+  console.log("Done!");
+}
+
+export default await main();
+