This post was adapted from an earlier Twitter thread.
It's incredible how many collective developer hours have been wasted on pushing through the turd that is ES Modules (often mistakenly called "ES6 Modules"). Causing a big ecosystem divide and massive tooling support issues, for... well, no reason, really. There are no actual advantages to it. At all.
It looks shiny and new and some libraries use it in their documentation without any explanation, so people assume that it's the new thing that must be used. And then I end up having to explain to them why, unlike CommonJS, it doesn't actually work everywhere yet, and may never do so. For example, you can't import ESM modules from a CommonJS file! (Update: I've released a module that works around this issue.)
And then there's Rollup, which apparently requires ESM to be used, at least to get things like treeshaking. Which then makes people believe that treeshaking is not possible with CommonJS modules. Well, it is - Rollup just chose not to support it.
And then there's Babel, which tried to transpile import
/export
to require
/module.exports
, sidestepping the ongoing effort of standardizing the module semantics for ESM, causing broken imports and require("foo").default
nonsense and spec design issues all over the place.
And then people go "but you can use ESM in browsers without a build step!", apparently not realizing that that is an utterly useless feature because loading a full dependency tree over the network would be unreasonably and unavoidably slow - you'd need as many roundtrips as there are levels of depth in your dependency tree - and so you need some kind of build step anyway, eliminating this entire supposed benefit.
And then people go "well you can statically analyze it better!", apparently not realizing that ESM doesn't actually change any of the JS semantics other than the import
/export
syntax, and that the import
/export
statements are equally analyzable as top-level require
/module.exports
.
"But in CommonJS you can use those elsewhere too, and that breaks static analyzers!", I hear you say. Well, yes, absolutely. But that is inherent in dynamic imports, which by the way, ESM also supports with its dynamic import()
syntax. So it doesn't solve that either! Any static analyzer still needs to deal with the case of dynamic imports somehow - it's just rearranging deck chairs on the Titanic.
And then, people go "but now we at least have a standard module system!", apparently not realizing that CommonJS was literally that, the result of an attempt to standardize the various competing module systems in JS. Which, against all odds, actually succeeded!
... and then promptly got destroyed by ESM, which reintroduced a split and all sorts of incompatibility in the ecosystem, rather than just importing some updated variant of CommonJS into the language specification, which would have sidestepped almost all of these issues.
And while the initial CommonJS standardization effort succeeded due to none of the competing module systems being in particularly widespread use yet, CommonJS is so ubiquitous in Javascript-land nowadays that it will never fully go away. Which means that runtimes will forever have to keep supporting two module systems, and developers will forever be paying the cost of the interoperability issues between them.
Is it really? The vast majority of people who believe they're currently using ESM, aren't even actually doing so - they're feeding their entire codebase through Babel, which deftly converts all of those snazzy import
and export
statements back into CommonJS syntax. Which works. So what's the point of the new module system again, if it all works with CommonJS anyway?
And it gets worse; import
and export
are designed as special-cased statements. Aside from the obvious problem of needing to learn a special syntax (which doesn't quite work like object destructuring) instead of reusing core language concepts, this is also a downgrade from CommonJS' require
, which is a first-class expression due to just being a function call.
That might sound irrelevant on the face of it, but it has very real consequences. For example, the following pattern is simply not possible with ESM:
const someInitializedModule = require("module-name")(someOptions);
Or how about this one? Also no longer possible:
const app = express();
// ...
app.use("/users", require("./routers/users"));
Having language features available as a first-class expression is one of the most desirable properties in language design; yet for some completely unclear reason, ESM proponents decided to remove that property. There's just no way anymore to directly combine an import
statement with some other JS syntax, whether or not the module path is statically specified.
The only way around this is with await import
, which would break the supposed static analyzer benefits, only work in async contexts, and even then require weird hacks with parentheses to make it work correctly.
It also means that you now need to make a choice: do you want to be able to use ESM-only dependencies, or do you want to have access to patterns like the above that help you keep your codebase maintainable? ESM or maintainability, your choice!
So, congratulations, ESM proponents. You've destroyed a successful userland specification, wasted many (hundreds of?) thousands of hours of collective developer time, many hours of my own personal unpaid time trying to support people with the fallout, and created ecosystem fragmentation that will never go away, in exchange for... fuck all.
This is a disaster, and the only remaining way I see to fix it is to stop trying to make ESM happen, and deprecate it in favour of some variant of CommonJS modules being absorbed into the spec. It's not too late yet; but at some point it will be.
And? That's an integral part of a tremendous number of projects. Even if it's refactored to ESM by it's new NX owners, they'll push far too many breaking changes for it to be worth it for fully functional projects to update. We're a decade out on that, guaranteed.
Even without lerna, it's a lib that could be as useful in node as it is in the browser, and thus should not be ESM only. Either way, if you think I went out of my way to pick that one, then feel free, but it just happened to be the most recent of my collisions with his libraries. I have exceptions in dependabot for
chalk
,ora
,globby
to name a few, as well asoverrides
in multiple package files, and for downstream fallout likeinquirer
as well (actually, still my belief: SBoudrias/Inquirer.js#1159 (comment)).But again, that's why I just went ahead and generated the real data. You can't really argue with the 7%. It's abysmal.
Then you are FAR too inexperienced in the industry to have a meaningful opinion. "Just rewrite all of your code" is what they said for python2 -> python3. "It'll be quick", they said. While we finally saw some linux distros drop it after 13 years, it's still not completely solved. It's the death knell of entire companies. You're literally asking an entire ecosystem with software that works to dedicate hundreds of billions of dollars for rewrites just because of your quasi-religious belief that in a "standard".
I've spent most of my career refactoring, TS for the last 3 years, half a dozen others for the 14 years prior. Strict TS, linting, test coverage, monorepos... the list goes on. It takes months, if not years. But I also spent years consulting for Fortune <20-1000>, and there's not a chance in hell that any of them are going to pay a second time for a product that already works. Go ahead and insert some anti-corporate nonsense here like the post cited above. You'll help prove my point.
If you work on small projects -- especially those with "new framework-itis" -- it might seem like a small thing to just "convert the entirety" because some other dude on the Internet said "trust me bro, it's the future".
Well, just read the list.
Otherwise, I've already. stated. them. before
But you're missing the point. nodejs cannot be ESM only until EVERY SINGLE NODE APP IS ESM ONLY. They have a contract of backwards compatibility, as every software platform should. ECMA decided to fix half of the problem and break the other half that already worked. Thus, we'll never get past this without revisions of that broken spec.
You can read my comments above. I'm not suggesting that commonjs is better. I don't think that there is even much contention that ESM syntax is better. But the ESM spec enforced runtime constraints that were -- and still are -- incompatible with half of the ecosystem. It's not going to just work itself out. Post a date when it'll be complete here, and I'll cite it in a post years from now like above when it doesn't happen. ESM needs to change, or it will eventually overtake the python conversion as "the worst decision smart people ever made" in the software industry.
Thank you. Yes, that's the primary issue.