pg-protocol: issue with imports in 1.9.0 with webpack

[colatkinson]

When bundling code with 1.9.0, we're hitting issues related to the new ESM wrapper.

During build, webpack prints a bunch of these warnings:

WARNING in ../node_modules/pg-protocol/esm/index.js 11:15-23
export 'default' (imported as 'protocol') was not found in '../dist/index.js' (possible exports: DatabaseError, __esModule, parse, serialize)

At runtime, the code fails to execute with the following error:

webpack://redacted/node_modules/pg-protocol/esm/index.js:5
export const DatabaseError = protocol.DatabaseError
                             ^


TypeError: Cannot read properties of undefined (reading 'DatabaseError')
    at Object.11078 (webpack://redacted/node_modules/pg-protocol/esm/index.js:5:30)
    ...

Looking at the way imports are done in the ESM wrapper:

node-postgres/packages/pg-protocol/esm/index.js

Line 2 in e8280d5

import protocol from '../dist/index.js'

This seems to assume a default export from dist/index.js. Copying the generated code below:

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.DatabaseError = exports.serialize = exports.parse = void 0;
const messages_1 = require("./messages");
Object.defineProperty(exports, "DatabaseError", { enumerable: true, get: function () { return messages_1.DatabaseError; } });
const serializer_1 = require("./serializer");
Object.defineProperty(exports, "serialize", { enumerable: true, get: function () { return serializer_1.serialize; } });
const parser_1 = require("./parser");
function parse(stream, callback) {
    const parser = new parser_1.Parser();
    stream.on('data', (buffer) => parser.parse(buffer, callback));
    return new Promise((resolve) => stream.on('end', () => resolve()));
}
exports.parse = parse;
//# sourceMappingURL=index.js.map

I believe that node (at least as of 20.19) works around this with a "synthetic" default export. However webpack, because the code sets exports.__esModule = true, treats this as an ESM module and thus doesn't shim a default where there is none.

To resolve this, both of these approaches seem to work in some quick testing:

1. Change the import to import * as protocol from '../dist/index.js' . I believe this is correct with regards to how ESM imports are supposed to work.
2. Change tsconfig to generate code that isn't marked as an ES module (i.e. doesn't generate that __esModule stub). Removing this line by hand seems to work, though I have no idea which set of levers to pull to effect this change in the actual codegen.

Happy to contribute a PR towards a fix if either of these or an alternative approach sounds feasible.

Alternatively, if this is simply too far outside supported use cases, feel free to close. It's possible to work around by adding a

{
    resolve: {
        alias: {
            "pg-protocol": path.resolve(__dirname, "node_modules/pg-protocol/dist/index.js"),
        },
    },
}

to the webpack.config.js.

[brianc]

nice! sorry for breaking that...trying to add esm support has been quite a bit more brittle and fraught with footguns than I expected it to be! I think option 1. is probably the right approach, provided you can't think of any way it could break something else being imported some way out in the wide world of node! And also that it isn't any kind of breaking change...though it sounds like basically a 1 liner change w/o any side effects...

Alternatively, if this is simply too far outside supported use cases, feel free to close. It's possible to work around by adding a

appreciate that thought, but if it used to work and now it doesn't work I'd certainly rather fix it then just add a "naw you fix that w/ a webpack hack on your end" answer. ❤

[brianc]

@colatkinson since I was already changing some other stuff I went ahead and added the change. Seems to be fine and don't impact anything outside webpack....Look good to you?

[colatkinson]

@brianc Yup that seems to have done the trick! Thanks for the quick turnaround.

One additional warning did pop up, but seems noncritical:

WARNING in ../node_modules/pg-protocol/esm/index.js 6:20-33
export 'SASL' (imported as 'protocol') was not found in '../dist/index.js' (possible exports: DatabaseError, __esModule, parse, serialize)

Seems to just be that object legitimately not being present.

Anyway feel free to close this out!

[brianc]

sweet, ty!

[bk201-]

@brianc
Why was this issue closed without PR? It is still the issue which reproduces as easy as to fix this.

The SASL is still not exist in index.js or this export is not needed