fix: error when using top level await and outputting commonjs module

README.md

@@ -18,7 +18,7 @@ There are several steps done in a pipeline:
    - Allows mapping any specifier to an npm package.
 1. Type checks the output.
 1. Emits ESM, CommonJS, and TypeScript declaration files along with a _package.json_ file.
-1. Runs the final output in Node through a test runner running all `Deno.test` calls. Deletes the test files when complete.
+1. Runs the final output in Node through a test runner calling all `Deno.test` calls.
 
 ## Setup
 

lib/compiler.test.ts

@@ -1,4 +1,8 @@
-import { getCompilerScriptTarget, ScriptTarget } from "./compiler.ts";
+import {
+  getCompilerScriptTarget,
+  getTopLevelAwait,
+  ScriptTarget,
+} from "./compiler.ts";
 import { ts } from "./mod.deps.ts";
 import { assertEquals, assertThrows } from "./test.deps.ts";
 
@@ -26,3 +30,21 @@ Deno.test("script target should have expected outputs", () => {
   assertEquals(getCompilerScriptTarget(undefined), ts.ScriptTarget.ES2021);
   assertThrows(() => getCompilerScriptTarget("invalid" as any));
 });
+
+Deno.test("get has top level await", () => {
+  runTest("const some = code;class SomeOtherCode {}", undefined);
+  runTest("async function test() { await 5; }", undefined);
+  runTest("await test();", {
+    line: 0,
+    character: 0,
+  });
+
+  function runTest(code: string, expected: ts.LineAndCharacter | undefined) {
+    const sourceFile = ts.createSourceFile(
+      "file.ts",
+      code,
+      ts.ScriptTarget.Latest,
+    );
+    assertEquals(getTopLevelAwait(sourceFile), expected);
+  }
+});

lib/compiler.ts

@@ -50,3 +50,17 @@ export function getCompilerScriptTarget(target: ScriptTarget | undefined) {
       throw new Error(`Unknown target compiler option: ${target}`);
   }
 }
+
+export function getTopLevelAwait(sourceFile: ts.SourceFile) {
+  for (const statement of sourceFile.statements) {
+    if (
+      ts.isExpressionStatement(statement) &&
+      ts.isAwaitExpression(statement.expression)
+    ) {
+      return sourceFile.getLineAndCharacterOfPosition(
+        statement.expression.getStart(sourceFile),
+      );
+    }
+  }
+  return undefined;
+}

mod.ts

@@ -1,6 +1,10 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
-import { getCompilerScriptTarget, outputDiagnostics } from "./lib/compiler.ts";
+import {
+  getCompilerScriptTarget,
+  getTopLevelAwait,
+  outputDiagnostics,
+} from "./lib/compiler.ts";
 import { colors, createProjectSync, path, ts } from "./lib/mod.deps.ts";
 import { PackageJsonObject } from "./lib/types.ts";
 import { glob, runNpmCommand } from "./lib/utils.ts";
@@ -153,7 +157,7 @@ export async function build(options: BuildOptions): Promise<void> {
       jsxFactory: "React.createElement",
       jsxFragmentFactory: "React.Fragment",
       importsNotUsedAsValues: ts.ImportsNotUsedAsValues.Remove,
-      module: ts.ModuleKind.ES2015,
+      module: ts.ModuleKind.ESNext,
       moduleResolution: ts.ModuleResolutionKind.NodeJs,
       target: getCompilerScriptTarget(options.compilerOptions?.target),
       allowSyntheticDefaultImports: true,
@@ -182,11 +186,25 @@ export async function build(options: BuildOptions): Promise<void> {
     const outputFileText = binaryEntryPointPaths.has(outputFile.filePath)
       ? `#!/usr/bin/env node\n${outputFile.fileText}`
       : outputFile.fileText;
-    project.createSourceFile(
+    const sourceFile = project.createSourceFile(
       outputFilePath,
       outputFileText,
     );
 
+    const tlaLocation = getTopLevelAwait(sourceFile);
+    if (tlaLocation) {
+      warn(
+        `Top level await cannot be used when targeting CommonJS ` +
+          `(See ${outputFile.filePath} ${tlaLocation.line + 1}:${
+            tlaLocation.character + 1
+          }). ` +
+          `Please re-organize your code to not use a top level await or only distribute an ESM module.`,
+      );
+      throw new Error(
+        "Build failed due to top level await when creating CommonJS module.",
+      );
+    }
+
     if (!options.skipSourceOutput) {
       writeFile(outputFilePath, outputFileText);
     }

tests/integration.test.ts

@@ -1,10 +1,13 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
-import { assertEquals } from "https://deno.land/[email protected]/testing/asserts.ts";
+import {
+  assertEquals,
+  assertRejects,
+} from "https://deno.land/[email protected]/testing/asserts.ts";
 import { build, BuildOptions } from "../mod.ts";
 
 Deno.test("should build", async () => {
-  await runTest({
+  await runTest("test_project", {
     entryPoints: ["mod.ts"],
     outDir: "./npm",
     package: {
@@ -55,7 +58,7 @@ test_runner.js
 });
 
 Deno.test("should build bin project", async () => {
-  await runTest({
+  await runTest("test_project", {
     entryPoints: [{
       kind: "bin",
       name: "add",
@@ -98,30 +101,46 @@ Deno.test("should build bin project", async () => {
   });
 });
 
+Deno.test("error for project with TLA and creating a CommonJS", async () => {
+  await assertRejects(() =>
+    runTest("tla_project", {
+      entryPoints: ["mod.ts"],
+      outDir: "./npm",
+      package: {
+        name: "add",
+        version: "1.0.0",
+      },
+    })
+  );
+});
+
 export interface Output {
   packageJson: any;
   npmIgnore: string;
   getFileText(filePath: string): string;
 }
 
 async function runTest(
+  project: "test_project" | "tla_project",
   options: BuildOptions,
-  checkOutput: (output: Output) => (Promise<void> | void),
+  checkOutput?: (output: Output) => (Promise<void> | void),
 ) {
   const originalCwd = Deno.cwd();
-  Deno.chdir("./tests/test_project");
+  Deno.chdir(`./tests/${project}`);
   try {
     await build(options);
     const getFileText = (filePath: string) => {
       return Deno.readTextFileSync(options.outDir + "/" + filePath);
     };
-    const packageJson = JSON.parse(getFileText("package.json"));
-    const npmIgnore = getFileText(".npmignore");
-    await checkOutput({
-      packageJson,
-      npmIgnore,
-      getFileText,
-    });
+    if (checkOutput) {
+      const packageJson = JSON.parse(getFileText("package.json"));
+      const npmIgnore = getFileText(".npmignore");
+      await checkOutput({
+        packageJson,
+        npmIgnore,
+        getFileText,
+      });
+    }
   } finally {
     Deno.removeSync(options.outDir, { recursive: true });
     Deno.chdir(originalCwd);

tests/tla_project/mod.test.ts

@@ -0,0 +1,9 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+import { add } from "./mod.ts";
+
+Deno.test("should add in test project", () => {
+  if (add(1, 2) !== 3) {
+    throw new Error("FAIL");
+  }
+});

tests/tla_project/mod.ts

@@ -0,0 +1,7 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+await new Promise<void>((resolve) => resolve());
+
+export function add(a: number, b: number) {
+  return a + b;
+}

todo.txt

@@ -1,4 +1,3 @@
-- tests for `build`
 - Handle deno-types when it specifies a declaration for a `.ts` file (maybe transform the .ts file to .js?)
 - Handle dynamic imports (at least ones that are statically analyzable and maybe warn on others)
 - Support lockfile