• Are you running the latest version?
• Have you included sample input, output, error, and expected output?
• Have you checked if you are using correct configuration?
• Did you try online tool?
• Have you checked the docs for helpful APIs and examples?

Description

When targeting both ESM and CommonJS for TypeScript, the CommonJS targeting will error with the following:

error TS1479: The current file is a CommonJS module whose imports will produce 'require' calls; however, the referenced file is an ECMAScript module and cannot be imported with 'require'. Consider writing a dynamic 'import("fast-xml-parser")' call instead.
  To convert this file to an ECMAScript module, change its file extension to '.mts' or create a local package.json file with `{ "type": "module" }`.

4 import { XMLBuilder, XMLParser, XMLValidator } from "fast-xml-parser";

The issue is that you are shipping a single set of types for both ESM and CommonJS as noted here:

  "exports": {
    ".": {
      "import": "./src/fxp.js",
      "require": "./lib/fxp.cjs",
      "types": "./src/fxp.d.ts",
      "default": "./src/fxp.js"
    }
  },

In this case you are shipping your ESM types, ./src/fxp.d.ts for both ESM and CJS, which is a bug as noted on Are the Types Wrong? - fast-xml-parser

This gives helpful hints that this library is masquerading as ESM, and instead you should ship both a set of types for CommonJS and ESM such as the following:

  "exports": {
    ".": {
      "import": {
        "types": "./dist/esm/index.d.ts",
        "default": "./dist/esm/index.js"
      },
      "require": {
        "types": "./dist/commonjs/index.d.ts",
        "default": "./dist/commonjs/index.js"
      }
    }
  },

Input

Upgrading the @azure/core-xml project to use the latest fast-xml-parser as noted here: Azure/azure-sdk-for-js#33172 (comment)

Code

This code will fail if we are using the targeting for CommonJS:

import { XMLBuilder, XMLParser, XMLValidator } from "fast-xml-parser";

We can get rid of the overall compiler error with @ts-ignore but this is not ideal

@ts-ignore
import { XMLBuilder, XMLParser, XMLValidator } from "fast-xml-parser";

Output

error TS1479: The current file is a CommonJS module whose imports will produce 'require' calls; however, the referenced file is an ECMAScript module and cannot be imported with 'require'. Consider writing a dynamic 'import("fast-xml-parser")' call instead.
  To convert this file to an ECMAScript module, change its file extension to '.mts' or create a local package.json file with `{ "type": "module" }`.

4 import { XMLBuilder, XMLParser, XMLValidator } from "fast-xml-parser";

expected data

Expected to compile, however does not unless using @ts-ignore.

Would you like to work on this issue?

• Yes
• No

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