The meteor/tools/isobuild/resolver.js changes are the static half of the
puzzle. The runtime half was implemented in install@0.13.0 with this
commit: 233aa75ce3
We don't need to build a whole new dev bundle just for this upgrade, since
we've already worked around the bug that it fixes, but it will get picked
up the next time we build the dev bundle for Meteor 1.8.2.
This ensures we wrap modules with a function to rename the `module`
identifier to something more reliable when the ImportScanner compiles
unanticipated modules imported from node_modules.
Should fix#10595.
Code from the application `node_modules` directory becomes part of the
`modules` package, so that it can be imported by any other package that
uses the module system, regardless of package load order.
Now that we compile code from `node_modules` using `babel-compiler` and
`meteor-babel` (#10585), `node_modules` code requires the same runtime
environment as any other Meteor JS code. For the most part, this need is
satisfied by the `@babel/runtime/helpers/...` modules, which are also
defined in the `modules` package because they come from `node_modules`.
However, in the legacy bundle, `meteorBabelHelpers.sanitizeForInObject` is
used to fix buggy for-in iteration in older Internet Explorers.
Thankfully, this extra helper code does not need to be included in the
modern or server bundles, but only in legacy code.
Case in point: @babel/runtime/helpers/esm/typeof.js uses ECMAScript module
syntax (import, export), but must not be compiled with transforms like
@babel/plugin-transform-typeof-symbol, since it's part of the runtime
library depended upon by that transform.
This logic is an extreme implementation detail for sure, but at least
babel-compiler is the only code that needs to know about this complexity.
Now that we have the ability to invoke Babel via compiler plugins for
individual modules encountered by the ImportScanner, it's possible the
ImportScanner will try to compile @babel/runtime/helpers/* modules.
These modules are not safe to recompile because they use native syntax
(such as typeof) in ways that do not need additional transformation or
simulation, and would be broken by applying the usual Babel transforms.
It may bother you that this list of packages is hard-coded, or that it
might grow over time. To ease those concerns, I would say:
1. We can release new versions of the babel-compiler and ecmascript
packages whenever we need to.
2. These particular npm packages belong in this list because Babel
itself assumes they have already been compiled, so there shouldn't be
(m)any other packages that fit that narrow criterion.
In other words, this is just a list of packages that must be left
untouched in order to bootstrap the Babel compiler system, and the
babel-compiler package is where the details of that system primarily
reside, so that's where we should put this list, until/unless we find a
better solution.
* Update ecmascript-runtime-{client,server} to core-js@3.1.4.
Also added a polyfill for Symbol.asyncIterator to server, modern, and
legacy, which should fix#9897.
* Add a test of for-await-of async iteration.
This should verify that #9897 is fixed.
