Unable to import symbols exported from imported modules

[dandv]

I'm trying to use d3-dsv in a script run with --experimental-modules. When importing one of the symbols that d3-dsv exports from imported modules, I get:

$ npm install d3-dsv
$ echo "import { csvFormat } from 'd3-dsv'" > exp.mjs
$ node --experimental-modules exp.mjs
(node:29364) ExperimentalWarning: The ESM module loader is experimental.
SyntaxError: The requested module does not provide an export named 'csvFormat'
    at ModuleJob._instantiate (internal/loader/ModuleJob.js:84:17)
    at <anonymous>

This works with Babel:

$ node -r babel-register exp.mjs  # OK
$ node -v
v9.3.0

A workaround is to import everything...

import d3 from 'd3-dsv';
d3.csvFormat([]);

...but that's not backwards compatible

$ node -r babel-register exp.mjs
exp.mjs:9
_d3Dsv2.default.csvFormat([]);
                ^

TypeError: Cannot read property 'csvFormat' of undefined
    at Object.<anonymous> (exp.mjs:2:4)
    at Module._compile (module.js:660:30)
    at loader (node_modules/babel-register/lib/node.js:144:5)
    at Object.require.extensions.(anonymous function) [as .js] (node_modules/babel-register/lib/node.js:154:7)
    at Module.load (module.js:573:32)
    at tryModuleLoad (module.js:513:12)
    at Function.Module._load (module.js:505:3)
    at Function.Module.runMain (module.js:701:10)
    at startup (bootstrap_node.js:194:16)
    at bootstrap_node.js:618:3

Alternatively, importing the whole module fails and using property notation with --experimental-modules:

import * as d3 from 'd3-dsv';
d3.csvFormat([]);

$ node --experimental-modules exp.mjs
(node:31199) ExperimentalWarning: The ESM module loader is experimental.
TypeError: d3.csvFormat is not a function
    at exp.mjs:2:4
    at ModuleJob.run (internal/loader/ModuleJob.js:96:14)
    at <anonymous>

[bnoordhuis]

See "main" in its package.json, that file you link to is not its entry point.

Closing, no reason to believe this is a bug in node.js.

[bnoordhuis]

Forgot to mention, if you just wanted to ask a question instead of report a bug, please use the help repo for that.

[dandv]

CC @mbostock - how should ES6 modules import d3-dsv?

[mbostock]

The expected pattern is

import {csvFormat} from "d3-dsv";

However, you’ll need an environment that supports the module entry in package.json (I recommend @ std/esm). (An environment that supports interoperability by importing from a CommonJS bundle would also work, but is a bit silly given that d3-dsv is authored in ES modules.)