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feat: output uses "type": "module" when esModule is set to true #478

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9a79878
Add ES module support with "type": "module" in package.json
tichopad Sep 16, 2025
6f2a25f
Exclude no-import-prefix rule, specify @std/csv version and fix forma…
tichopad Sep 20, 2025
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3 changes: 2 additions & 1 deletion deno.jsonc
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,8 @@
"rules": {
"exclude": [
"no-explicit-any",
"camelcase"
"camelcase",
"no-import-prefix"
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@tichopad tichopad Sep 20, 2025

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I've run into linter issues with the existing code using inline imports. This rule got added to the default ruleset in Deno 2.5.

My assumption is the project's okay with inline imports, so I decided to exclude the rule instead. Let me know if I should rather refactor inline imports instead.

]
}
},
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3 changes: 2 additions & 1 deletion deno.lock
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8 changes: 8 additions & 0 deletions lib/package_json.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,7 @@ Deno.test("single entrypoint", () => {
assertEquals(getPackageJson(props), {
name: "package",
version: "0.1.0",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
types: "./types/mod.d.ts",
Expand Down Expand Up @@ -93,6 +94,7 @@ Deno.test("single entrypoint", () => {
{
name: "package",
version: "0.1.0",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
types: "./types/mod.d.ts",
Expand Down Expand Up @@ -128,6 +130,7 @@ Deno.test("single entrypoint", () => {
{
name: "package",
version: "0.1.0",
type: "module",
main: undefined,
module: "./esm/mod.js",
types: "./types/mod.d.ts",
Expand Down Expand Up @@ -184,6 +187,7 @@ Deno.test("single entrypoint", () => {
{
name: "package",
version: "0.1.0",
type: "module",
main: undefined,
module: "./esm/mod.js",
types: undefined,
Expand Down Expand Up @@ -216,6 +220,7 @@ Deno.test("single entrypoint", () => {
{
name: "package",
version: "0.1.0",
type: "module",
main: undefined,
module: "./esm/mod.js",
types: undefined,
Expand Down Expand Up @@ -324,6 +329,7 @@ Deno.test("multiple entrypoints", () => {
version: "0.1.0",
main: "./script/mod.js",
module: "./esm/mod.js",
type: "module",
types: "./types/mod.d.ts",
dependencies: {
"@deno/shim-deno": "~0.1.0",
Expand Down Expand Up @@ -401,6 +407,7 @@ Deno.test("binary entrypoints", () => {
version: "0.1.0",
main: "./script/mod.js",
module: "./esm/mod.js",
type: "module",
types: "./types/mod.d.ts",
bin: {
my_bin: "./esm/bin.js",
Expand Down Expand Up @@ -501,6 +508,7 @@ Deno.test("peer dependencies", () => {
scripts: {
test: "node test_runner.js",
},
type: "module",
dependencies: {
dep: "^1.0.0",
},
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9 changes: 9 additions & 0 deletions lib/package_json.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,14 @@ export function getPackageJson({
path: e.replace(/\.tsx?$/i, ".js"),
types: e.replace(/\.tsx?$/i, ".d.ts"),
}));
// include "type" field if we are including esm
const type = {
...(includeEsModule
? {
type: "module",
}
: {}),
};
Comment on lines +39 to +45
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@tichopad tichopad Sep 20, 2025

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Includes "type": "module" if esModule: true, otherwise doesn't add the type field at all.
It also still allows the user to explictly overwrite the type field via the build function's config.

const exports = finalEntryPoints.filter((e) => e.kind === "export");
const binaries = finalEntryPoints.filter((e) => e.kind === "bin");
const dependencies = {
Expand Down Expand Up @@ -111,6 +119,7 @@ export function getPackageJson({
const final: Record<string, unknown> = {
...mainExport,
...binaryExport,
...type,
...packageJsonObj,
scripts: {},
...deleteEmptyKeys({
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15 changes: 12 additions & 3 deletions lib/test_runner/get_test_runner_code.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,10 @@ Deno.test("gets code when no shim used", () => {
});
assertEquals(
code,
`const pc = require("picocolors");
`import { createRequire } from 'module';
const require = createRequire(import.meta.url);
const __dirname = new URL(".", import.meta.url).pathname;
const pc = require("picocolors");
const process = require("process");

const filePaths = [
Expand Down Expand Up @@ -60,7 +63,10 @@ Deno.test("gets code when shim used", () => {
});
assertEquals(
code,
`const pc = require("picocolors");
`import { createRequire } from 'module';
const require = createRequire(import.meta.url);
const __dirname = new URL(".", import.meta.url).pathname;
const pc = require("picocolors");
const process = require("process");
const { pathToFileURL } = require("url");
const { testDefinitions } = require("test-shim-package/test-internals");
Expand Down Expand Up @@ -123,7 +129,10 @@ Deno.test("gets code when cjs is not used", () => {
});
assertEquals(
code,
`const pc = require("picocolors");
`import { createRequire } from 'module';
const require = createRequire(import.meta.url);
const __dirname = new URL(".", import.meta.url).pathname;
const pc = require("picocolors");
const process = require("process");

const filePaths = [
Expand Down
10 changes: 10 additions & 0 deletions lib/test_runner/get_test_runner_code.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,16 @@ export function getTestRunnerCode(options: {
}) {
const usesDenoTest = options.denoTestShimPackageName != null;
const writer = createWriter();

if (options.includeEsModule) {
// ensure compatibility with esm ("type": "module")
writer.writeLine(`import { createRequire } from 'module';`);
writer.writeLine(`const require = createRequire(import.meta.url);`);
writer.writeLine(
`const __dirname = new URL(".", import.meta.url).pathname;`,
);
}
Comment on lines +15 to +22
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@tichopad tichopad Sep 20, 2025

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I considered polyfilling the safer way to enable ESM compatibility instead of outputting ES modules directly.


writer.writeLine(`const pc = require("picocolors");`)
.writeLine(`const process = require("process");`);
if (usesDenoTest) {
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10 changes: 10 additions & 0 deletions tests/integration.test.ts
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Expand Up @@ -63,6 +63,7 @@ Deno.test("should build test project - basic", async () => {
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
exports: {
Expand Down Expand Up @@ -211,6 +212,7 @@ Deno.test("should build with all options off", async () => {
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
module: "./esm/mod.js",
exports: {
".": {
Expand Down Expand Up @@ -288,6 +290,7 @@ Deno.test("should build test project with declarations inline by default", async
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
exports: {
Expand Down Expand Up @@ -369,6 +372,7 @@ Deno.test("should build bin project", async () => {
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
bin: {
add: "./esm/mod.js",
},
Expand Down Expand Up @@ -414,6 +418,7 @@ Deno.test("should build bin project with a shebang", async () => {
assertEquals(output.packageJson, {
name: "hello",
version: "1.0.0",
type: "module",
bin: {
hello: "./esm/main.js",
},
Expand Down Expand Up @@ -505,6 +510,7 @@ Deno.test("not error for TLA when not using CommonJS", async () => {
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
module: "./esm/mod.js",
exports: {
".": {
Expand Down Expand Up @@ -621,6 +627,7 @@ Deno.test("should build with package mappings", async () => {
assertEquals(output.packageJson, {
name: "mappings",
version: "1.2.3",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
exports: {
Expand Down Expand Up @@ -690,6 +697,7 @@ Deno.test("should build with peer dependencies in mappings", async () => {
assertEquals(output.packageJson, {
name: "mappings",
version: "1.2.3",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
exports: {
Expand Down Expand Up @@ -1162,6 +1170,7 @@ Deno.test("should build jsr project", async () => {
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
exports: {
Expand Down Expand Up @@ -1232,6 +1241,7 @@ Deno.test("should build workspace project", async () => {
assertEquals(output.packageJson, {
name: "add",
version: "1.0.0",
type: "module",
main: "./script/mod.js",
module: "./esm/mod.js",
exports: {
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2 changes: 1 addition & 1 deletion tests/jsr_project/mod.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
// Copyright 2018-2024 the Deno authors. MIT license.

import { parse } from "jsr:@std/csv/parse";
import { parse } from "jsr:@std/csv@1.0.6/parse";
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@tichopad tichopad Sep 20, 2025

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I added a version specifier to fix a linter error. The version used is based on the latest @std/csv version specified in deno.lock.

import { assertEquals } from "jsr:@std/[email protected]/assert-equals";
import * as fs from "node:fs";

Expand Down
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