Add modern ESM Support #74

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nrcrast wants to merge 5 commits into sagold:main from nrcrast:esm-support

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Add modern ESM Support #74

nrcrast wants to merge 5 commits into sagold:main from nrcrast:esm-support

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@nrcrast

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@nrcrast nrcrast commented Jun 17, 2025

Fix #59

This updates the tsconfig and package.json (and all the other consequences of that) to export proper ESM modules.

You can test this pretty easily with a project like the following:

package.json

{
 "name": "json-validator-test",
 "version": "1.0.0",
 "type": "module",
 "scripts": {
 "start": "node src/index.js",
 "test": "echo \"Error: no test specified\" && exit 1"
 },
 "author": "",
 "license": "ISC",
 "description": "",
 "dependencies": {
 "json-schema-library": "10.5.2",
 "tsx": "^4.19.3"
 },
 "devDependencies": {
 "@types/node": "^24.0.3",
 "typescript": "^5.8.3"
 }
}

src/index.js

import {compileSchema} from "json-schema-library";
const schema = compileSchema({
 "$id": "https://example.com/person.schema.json",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "title": "Person",
 "type": "object",
 "properties": {
 "firstName": {
 "type": "string",
 "description": "The person's first name."
 }
 }
});
console.log('Hello world', schema);

Using plain ole npm with node v22, running npm i && npm run start you'll get something like this:

file:///Users/206674672/code/json-validator-test/src/index.js:1
import {compileSchema} from "json-schema-library";
 ^^^^^^^^^^^^^
SyntaxError: Named export 'compileSchema' not found. The requested module 'json-schema-library' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:
import pkg from 'json-schema-library';
const {compileSchema} = pkg;
 at ModuleJob._instantiate (node:internal/modules/esm/module_job:177:21)
 at async ModuleJob.run (node:internal/modules/esm/module_job:260:5)
 at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:543:26)
 at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:116:5)

Replacing the version with my branch: :

 "json-schema-library": "git@github.com:nrcrast/json-schema-library.git#66bb39f1b68d518ee67707d88ea0598dec7e8a51",

You'll get the expected output where it dumps the whole compiled schema:

> json-validator-test@1.0.0 start
> node src/index.js
Hello world <ref *1> {
 evaluationPath: '#',
 lastIdPointer: '#',
 schemaLocation: '#',
 dynamicId: '',
....etc

Crast, Nick (NBCUniversal) added 5 commits

June 17, 2025 15:58


 Add exports to package json

aa77b54


 Remove require for now

87232d3


 Update tsconfig

46e76ae


 Update bad references

c03456a


 Webpack formatting

66bb39f

@sagold sagold added the enhancement label

Jul 2, 2025

@sagold

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sagold commented Jul 2, 2025

Hi Nick,

thank you for your PR!! I will need some time to verify your changes and test other types of exports. I have a setup
prepared to build an esm module without those changes, but your PR might be a better way forward.

Cheers,
Sascha

@navnita123

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navnita123 commented Aug 24, 2025

Please release this, we need modern esm support

@sagold

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sagold commented Aug 27, 2025

Did you run yarn test? This is a prerequisite for me to further look into this PR. Currently the test run fails:

➜ json-schema-library git:(esm-support) yarn test
yarn run v1.22.19
$ mocha 'src/**/*.{test,spec}.ts'
XXX/json-schema-library/node_modules/mocha/lib/cli/config.js:80
 throw createUnparsableFileError(
 ^
Error: Unable to read/parse XXX/json-schema-library/.mocharc.js: Error [ERR_REQUIRE_ESM]: require() of ES Module XXX/json-schema-library/.mocharc.js from XXX/json-schema-library/node_modules/mocha/lib/cli/config.js not supported.
.mocharc.js is treated as an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which declares all .js files in that package scope as ES modules.
Instead either rename .mocharc.js to end in .cjs, change the requiring code to use dynamic import() which is available in all CommonJS modules, or change "type": "module" to "type": "commonjs" in XXX/json-schema-library/package.json to treat all .js files as CommonJS (using .mjs for all ES modules instead).
 at createUnparsableFileError (XXX/json-schema-library/node_modules/mocha/lib/errors.js:514:13)
 at exports.loadConfig (XXX/json-schema-library/node_modules/mocha/lib/cli/config.js:80:11)
 at loadRc (XXX/json-schema-library/node_modules/mocha/lib/cli/options.js:162:21)
 at loadOptions (XXX/json-schema-library/node_modules/mocha/lib/cli/options.js:250:20)
 at Object.<anonymous> (XXX/json-schema-library/node_modules/mocha/bin/mocha.js:27:14)
 at Module._compile (node:internal/modules/cjs/loader:1546:14)
 at Object..js (node:internal/modules/cjs/loader:1689:10)
 at Module.load (node:internal/modules/cjs/loader:1318:32)
 at Function._load (node:internal/modules/cjs/loader:1128:12)
 at TracingChannel.traceSync (node:diagnostics_channel:315:14) {
 code: 'ERR_MOCHA_UNPARSABLE_FILE'
}
Node.js v22.11.0

Be aware that I see the need of this feature (and I want this to be the next feature published), I am unhappy about the type of implementation. I would rather not change all source files, but build a valid esm package instead. Happy to discuss.