PERFORMANCE: import statements, ../lib/... paths and tree-shaking

[fpurcell]

A note about using .../lib/... paths on import statements:

In a future PR, I'm going to go thru all the files in otp-ui and switch all the .../lib/... import paths to .../src/... Cole pointed out that by us using transpiled .../lib/... code, we're preventing webpack from tree-shaking the otp-ui code (at a latter date / latter production build of an app), resulting in larger footprints than might be necessary (could be a big deal, esp if all the icons from the otp-ui Icons component are repeatedly pulled into everything we do -- esp. when we might only intend to use one or a small handful of those icons). We might do more, based on Cole's continued research in making the code performant.

IMPORTANT -- this is desired:

import utils from "@opentripplanner/core-utils";
center: utils.types.latlngType.isRequired,

was:
import { latlngType } from "@opentripplanner/core-utils/src/types";
center: latlngType.isRequired,

[fpurcell]

NOTE: Below is the original discussion on /src/ v. /lib/ ::

Cole Harper 2/11/2020, 11:16 AM

if you look at every import that has a /lib/ that is incorrect
its using the built version for some reason

Frank 2/11/2020, 11:18 AM

Hmm...
so this: import { transitVehicleType } from "@opentripplanner/core-utils/lib/types";
should be import { transitVehicleType } from "@opentripplanner/core-utils/src/types";

Cole Harper 2/11/2020, 11:32 AM Edited

@opentripplanner/core-utils or @opentripplanner/core-utils/types might be better

see this reach-ui example: https://github.com/reach/reach-ui/blob/master/packages/accordion/src/index.tsx

look at where it imports other @reach packages like import { createDescendantContext, DescendantProvider, useDescendant, useDescendants, } from "@reach/descendants";

Cole Harper 2/11/2020, 11:37 AM

opentripplanner/otp-ui
React component library, which can be used to build trip planner webapps. - opentripplanner/otp-ui

GitHub

IT looks like types is not exposed properly in the index.js https://github.com/opentripplanner/otp-ui/blob/c046416447367b6b66e060ad3b944e9ae8f70ba5/packages/core-utils/src/index.js

[fpurcell]

IMPORTANT: this is the desired format of imports of a file from a component / module:

import utils from "@opentripplanner/core-utils";

[landonreed]

There are a number of styled.js files that are not exported which may hinder the ability of implementers to achieve tree-shaking imports. cc @grant-humphries