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module: better error for named exports from cjs
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We do not support importing named exports from a CJS module.
This change decorates the error message for missing named exports in
the case where the module being imported is expected to be CJS by the
ESM loader.

Signed-off-by: Myles Borins <myles.borins@gmail.com>

PR-URL: #33256
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
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MylesBorins authored and codebytere committed Jun 7, 2020
1 parent 9dde1db commit 77caf92
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27 changes: 27 additions & 0 deletions lib/internal/modules/esm/module_job.js
@@ -1,10 +1,14 @@
'use strict';

const {
ArrayPrototypeJoin,
ObjectSetPrototypeOf,
PromiseAll,
SafeSet,
SafePromise,
StringPrototypeIncludes,
StringPrototypeMatch,
StringPrototypeSplit,
} = primordials;

const { ModuleWrap } = internalBinding('module_wrap');
Expand Down Expand Up @@ -93,6 +97,29 @@ class ModuleJob {
}
} catch (e) {
decorateErrorStack(e);
if (StringPrototypeIncludes(e.message,
' does not provide an export named')) {
const splitStack = StringPrototypeSplit(e.stack, '\n');
const parentFileUrl = splitStack[0];
const childSpecifier = StringPrototypeMatch(e.message, /module '(.*)' does/)[1];
const childFileURL =
await this.loader.resolve(childSpecifier, parentFileUrl);
const format = await this.loader.getFormat(childFileURL);
if (format === 'commonjs') {
const importStatement = splitStack[1];
const namedImports = StringPrototypeMatch(importStatement, /{.*}/)[0];
e.message = `The requested module '${childSpecifier}' is expected ` +
'to be of type CommonJS, which does not support named exports. ' +
'CommonJS modules can be imported by importing the default ' +
'export.\n' +
'For example:\n' +
`import pkg from '${childSpecifier}';\n` +
`const ${namedImports} = pkg;`;
const newStack = StringPrototypeSplit(e.stack, '\n');
newStack[3] = `SyntaxError: ${e.message}`;
e.stack = ArrayPrototypeJoin(newStack, '\n');
}
}
throw e;
}
for (const dependencyJob of jobsInGraph) {
Expand Down
64 changes: 64 additions & 0 deletions test/es-module/test-esm-cjs-named-error.mjs
@@ -0,0 +1,64 @@
import '../common/index.mjs';
import { rejects } from 'assert';

const fixtureBase = '../fixtures/es-modules/package-cjs-named-error';

const expectedRelative = 'The requested module \'./fail.cjs\' is expected to ' +
'be of type CommonJS, which does not support named exports. CommonJS ' +
'modules can be imported by importing the default export.\n' +
'For example:\n' +
'import pkg from \'./fail.cjs\';\n' +
'const { comeOn } = pkg;';

const expectedPackageHack = 'The requested module \'./json-hack/fail.js\' is ' +
'expected to be of type CommonJS, which does not support named exports. ' +
'CommonJS modules can be imported by importing the default export.\n' +
'For example:\n' +
'import pkg from \'./json-hack/fail.js\';\n' +
'const { comeOn } = pkg;';

const expectedBare = 'The requested module \'deep-fail\' is expected to ' +
'be of type CommonJS, which does not support named exports. CommonJS ' +
'modules can be imported by importing the default export.\n' +
'For example:\n' +
'import pkg from \'deep-fail\';\n' +
'const { comeOn } = pkg;';

rejects(async () => {
await import(`${fixtureBase}/single-quote.mjs`);
}, {
name: 'SyntaxError',
message: expectedRelative
}, 'should support relative specifiers with single quotes');

rejects(async () => {
await import(`${fixtureBase}/double-quote.mjs`);
}, {
name: 'SyntaxError',
message: expectedRelative
}, 'should support relative specifiers with double quotes');

rejects(async () => {
await import(`${fixtureBase}/json-hack.mjs`);
}, {
name: 'SyntaxError',
message: expectedPackageHack
}, 'should respect recursive package.json for module type');

rejects(async () => {
await import(`${fixtureBase}/bare-import-single.mjs`);
}, {
name: 'SyntaxError',
message: expectedBare
}, 'should support bare specifiers with single quotes');

rejects(async () => {
await import(`${fixtureBase}/bare-import-double.mjs`);
}, {
name: 'SyntaxError',
message: expectedBare
}, 'should support bare specifiers with double quotes');

rejects(async () => {
await import(`${fixtureBase}/escaped-single-quote.mjs`);
}, /import pkg from '\.\/oh'no\.cjs'/, 'should support relative specifiers with escaped single quote');
@@ -0,0 +1 @@
import { comeOn } from "deep-fail";
@@ -0,0 +1 @@
import { comeOn } from 'deep-fail';
@@ -0,0 +1 @@
import { comeOn } from "./fail.cjs";
@@ -0,0 +1 @@
import { value } from "./oh'no.cjs";
3 changes: 3 additions & 0 deletions test/fixtures/es-modules/package-cjs-named-error/fail.cjs
@@ -0,0 +1,3 @@
module.exports = {
comeOn: 'fhqwhgads'
};
@@ -0,0 +1 @@
import { comeOn } from './json-hack/fail.js';
@@ -0,0 +1,3 @@
module.exports = {
comeOn: 'fhqwhgads'
};
@@ -0,0 +1,3 @@
{
"type": "commonjs"
}

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3 changes: 3 additions & 0 deletions test/fixtures/es-modules/package-cjs-named-error/oh'no.cjs
@@ -0,0 +1,3 @@
module.exports = {
value: 123
};
5 changes: 5 additions & 0 deletions test/fixtures/es-modules/package-cjs-named-error/package.json
@@ -0,0 +1,5 @@
{
"name": "package-cjs-named-error",
"main": "index.mjs",
"type": "module"
}
@@ -0,0 +1 @@
import { comeOn } from './fail.cjs';

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