Trim low-hanging fruit to reduce bundle sizes (part 1 of issue #4324). #4234
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I just changed the target branch for this PR to |
This is not necessary. See tree shaking. Also discourage by some linters, for example: https://palantir.github.io/tslint/rules/no-submodule-imports/ |
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Agreed @danilobuerger Related, I PR'd standardized bundles in #4261:
The umd bundle is legacy and helps with putting your finger on the pulse of bundlesize (though not a foolproof indicator as it does not provide a tree shaken measurement). Users concerned with tree shaking should ensure they are using the targeted |
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"Discouraged by some linters" is right up there with "frowned upon by some uncles" in terms of how much it should motivate our decisions. Remember that these transforms would be optional, and would happen during the build step. If you're linting the code generated by your build pipeline (rather than your source code), you may be missing the point of linting? Not all bundlers do tree shaking, and not all tree-shaking bundlers do it reliably. Apollo is a set of libraries intended to be consumed in the widest possible variety of JavaScript environments, so I don't think we should be relying on the features of specific bundling tools. |
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@benjamn Your reply sounds rather rude to me, but I assume thats not on purpose. Now onto the content:
If I have to import like so: I will have that in my source code. So now a linter that warns / errors on submodules will warn / error.
How am I missing the point of linting?
So what. Thats not really an argument. The implementer can choose a bundler that supports tree-shaking or not. Its his decision that generates the output. |
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@danilobuerger I'm sorry for the way I phrased my previous comment, and I appreciate the correction. I would like to clarify what I thought you were talking about. You're right that having to write import { Something } from "apollo-client/core"would require using submodule imports in your source code, but the idea that you quoted in your original comment was a different one:
Since there's no As for exposing modules like
I think you may be over-focused on developers who have complete control over the software stack they have to work with. Speaking with the perspective of a library author, with customers who aren't able to use tree-shaking, I can assure you these (optional) features would have value, and they would complement whatever tree-shaking decisions the application developer may or may not be able to make. |
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Ah I see, just a misunderstanding. I should have quoted both examples in my initial reply, so its clear one is regarding tree shaking and the other regarding submodules. For me it wasn't clear that importing from So if I understand you correctly, the way to go would be: If thats the case, I agree. But then I see a minor new problem and thats documentation. We should be careful to not confuse (especially new to apollo) developers with the different import options and follow one path through out. |
Huge +1 on that. I learned a really painful tree shaking lesson when mixing cjs path imports with es index imports. Really flaky issue that there is no compatibility fix for. We should strongly encourage index imports to avoid interop problems and tree shaking optimization. Painful lesson details here: mui/material-ui-pickers#695 (comment) |
Absolutely agree. I'm imagining that all of our documentation examples should naively import everything from If the application developer is using a bundler that does tree-shaking (essentially Webpack, Rollup, or Parcel), then they shouldn't have to worry about optimizing bundle sizes. Practically speaking, that means we should design these packages so that tree-shaking actually works reliably in those three bundlers, given the simple If the application developer is not using a tree-shaking bundler, and they are worried about their bundle sizes, it would be great to have an intermediate/advanced section of the docs explaining some other options (e.g., adding a Babel transform to rewrite |
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After reading @rosskevin's most recent comment, I'm reminded that explicit sub-module imports don't benefit from the import { SomeESMThing } from "apollo-client/esm/core"instead of just By comparison, if everyone sticks to writing import { SomeThing } from "apollo-client"then the behavior will depend on the |
In what case would someone be concerned about bundle size, not use Webpack/Parcel but use babel? I just want to make sure we aren't putting attention to a small fraction of users. If you are concerned about bundlesize and you are using advanced tools like babel, you really should be using a bundler - straight away. What am I missing there? |
Exactly - this was a really painful lesson learned and I hope to help others avoid it. The only reason I have found to have exploded files is to match the My strong recommendation at this point (I just realized cc: @JoviDeCroock) would actually be to only use this format (which my PR is close but not quite there as I have
Now the above with package.json pointing to only rollup bundles would guarantee a user would not encounter interop problems I mentioned, but then would not provide any path imports either. Given the hidden interop problems, this seems like the best set of artifacts for the majority of users. I'm not sure path imports are a good tradeoff given the hidden downsides and implications to tree shaking. |
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@rosskevin You're right that the Venn diagram intersection is small, but one example is the Metro bundler used by React Native, which (last I checked, per facebook/metro#227) doesn't do tree-shaking. Arguably, tree shaking is a little less important in a React Native app, since you're not loading the code over a network, and tree-shaking is easier when you're building one big bundle, rather than doing incremental bundling on the fly, which I seem to recall being something Metro does? RN developers do use Babel plugins, though. |
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The easiest way to do this is to distribute es2018 in es modules. That would let app tools treeshake and transpile, and enable differential serving of small modern bundles to capable browsers aka >90 of your users (probably) https://mobile.twitter.com/jamiebuilds/status/1072180184290217985 This would also enable more modern work flows using browser standards like ESM and web components. Since transpiling and bundling should be largely app-level concerns, not library-level concerns, this would free developers to make lighter bundles and use innovative use cases. See also #3047 |
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@bennypowers I wish it was that easy, but this library still has to be consumable by applications/bundlers that use |
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That could be handled with Also, rollup and webpack can handle es modules, so why not just bump a major version, while distributing a legacy bundle with all the babel cruft included for those that need it? |
@bennypowers please see this comment as to why that is an interop problem #4234 (comment) and why I recommend rollup bundles for everything as detailed here #4234 (comment) |
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@bennypowers I would recommend moving that discussion to #4261, where @rosskevin is hard at work figuring out the best way to support all environments/bundlers. Once you get up to speed on the tradeoffs he's considering, I think you'll agree it's not a simple problem. ✌️ |
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Unrelated to the recent discussion, I'm beginning to realize that targeting |
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Part of #4224. This change reduces the minified+gzip'd bundle size of apollo-client from 10385 bytes to 9771 bytes, a ~6% decrease, according to this command: npx terser -m -c < lib/bundle.umd.js | gzip | wc -c As long as we're only building one bundle, and it has to work in the 15% minority of browsers that do not natively support async/await, we should avoid wasting precious bundle size on generator runtime code, especially since we had only one await expression in the entire package (so the runtime code was nowhere close to paying for itself).
If you look at the lib/bundle.umd.js files for the apollo-client packages,
you'll see multiple (re)declarations of TypeScript helpers like __extends,
__assign, and __rest. This happens because TypeScript injects those helper
function declarations into each module that uses them, so the declarations
appear multiple times when those compiled modules are concatenated.
Because the declarations share some identical code, gzip compression is
able to eliminate some of the repetition, but it would be better if each
helper appeared exactly once in each bundle.umd.js file.
One solution is to rely on a shared runtime library, which means putting
"importHelpers":true in your tsconfig.json file, and `npm install`ing the
tslib package, from which the helpers can be imported.
However, the tslib package contains all the helpers anyone could ever
need, which is far more than we actually need (about 2KB minified with
gzip, which is a lot). For this reason, we definitely do not want our
bundles to end up calling require("tslib") at any point.
Rollup to the rescue! By using rollup-plugin-node-resolve with { module:
true, only: ['tslib'] }, we can inline exactly the tslib exports that we
need, once, at the top of each bundle.umd.js file.
There will still be some overlap between the helpers declared by different
apollo-client packages, but at least now they will be exactly the same, so
gzip can work its magic with maximal efficiency.
Importing the whole GraphQL printer just for nicer errors isn't worth the extra bundle size. JSON.stringify isn't as pretty, but provides all the necessary information.
While knowing QueryDocumentKeys was helpful in theory, in practice we were importing the entire graphql/language/visitor module unnecessarily, and then had to tiptoe around the strange absence of primitive-valued keys (for example, QueryDocumentKeys.StringValue is an empty array, when it arguably should be ["value"]).
By privatizing the QueryManager, we give ourselves room to change its API in drastic ways without affecting the ApolloClient API.
We're only tracking fetchQuery promises in order to cancel the in-flight ones when clearStore is called, so we can get away with just storing the reject functions, thereby saving bundle size.
It's nice to be able to assume that (sub)queries with equivalent structure share the same object identities, but the cache will work without that assumption, and enforcing that discipline is not free, both in terms of runtime cost and in terms of bundle size. In the future, the `graphql-tag` tag package should provide a version of the `gql` template tag function that returns immutable structures that share object identity where possible. This commit alone saves 450ish bytes after minification and gzip!
This implementation has the following benefits: - It collapses the QueryScheduler abstraction into the QueryManager (which was always ultimately responsible for managing the lifetime of polling timers), thus simplifying the relationship between the QueryManager and its ObservableQuery objects. - It's about 100 bytes smaller than the previous implementation, after minification and gzip. - It uses setTimeout rather than setInterval, so event loop starvation never leads to a rapid succession of setInterval catch-up calls. - It guarantees at most one timeout will be pending for an arbitrary number of polling queries, rather than a separate timer for every distinct polling interval. - Fewer independent timers means better batching behavior, usually. - Though there may be a delay between the desired polling time for a given query and the actual polling time, the delay is never greater than the minimum polling interval across all queries, which changes dynamically as polling queries are started and stopped.
Though it's possible that someone might have been using flattenSelections directly, the function signature seems awfully specific to the needs of the former implementation of getDirectiveNames.
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We've decided to go ahead and merge/release the initial progress we've made in this PR, even though we are still a long way from the goal of cutting bundle sizes in half. Let's move the ongoing bundle size discussion to issue #4324. Thanks to everyone for the productive conversation so far! |
benjamn
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Part of issue #4324, whose description previously appeared here.
This PR contains a handful of relatively minor bundle size improvements of the "low-hanging fruit" variety. Before making deeper and more systematic changes (like introducing a production bundle), we wanted to identify and remove (or simplify) unnecessary (or unnecessarily complicated) code.