On the server, Meteor attempts to avoid bundling node_modules code by
replacing entry point modules with a stub that calls module.useNode() (see
packages/modules-runtime/server.js). This trick allows evaluating server
node_modules natively in Node.js, faithfully preserving all Node-specific
behaviors, such as module.id being an absolute file system path, the
__dirname and __filename variables, the ability to import binary .node
modules, and so on.
However, starting in Node.js 12.16.0 (Meteor 1.9.1+), modules evaluated
natively by Node are considered ECMAScript modules (ESM) if the closest
package.json file has "type": "module" (or has an .mjs file extension).
This poses a problem for the module.useNode() trick, because ESM modules
cannot be imported synchronously using require (which is currently how
module.useNode() works).
To work around this new error, this commit checks package.json for "type":
"module" in ImportScanner#shouldUseNode to determine whether it's safe to
use the module.useNode() trick.
The good news is that ESM modules don't have access to nearly as many
Node.js-specific quirks: no module, require, or exports variables; no
__dirname, no __filename; no ability to import JSON or other non-ESM file
types (at least right now). So it seems somewhat less important for ESM
code (compared to CommonJS code) to bail out into native Node.js execution
using module.useNode(). In other words, bundling server code should not
affect its execution in nearly as many cases, if that code is ESM rather
than legacy CommonJS.
If this good news turns out to be overly optimistic, we can consider using
a different kind of bailout stub that's capable of importing ESM using
dynamic import(). For now, making sure we avoid bailing out for ESM code
like @babel/runtime/helpers/esm/* is the priority.
Commit 646fa4e3eefixed#10547 by
restricting optimisticLookupPackageJson to package.json files with a
"name" property, which effectively skipped over intermediate package.json
files with additional properties.
However, in Node.js 12.16.0 (Meteor 1.9.1+), modules evaluated natively by
Node are considered ECMAScript modules if the closest package.json file
has "type": "module" (or has an .mjs file extension). This poses a problem
for the module.useNode() trick (see packages/modules-runtime/server.js),
because ESM modules cannot be imported using require.
For example, recent versions of the @babel/runtime package have a
@babel/runtime/helpers/esm/package.json file for the ESM versions of its
helpers (which specifies "type": "module"), but that package.json file
does not have a "name" property, because it is not the root package.json
file representing the entire @babel/runtime package.
I considered making the "name" restriction configurable, but that would
have fragmented the caching of optimisticLookupPackageJson. Instead, I
made it return an array of all potentially relevant package.json objects,
which can be safely cached.
This means that the caller has to iterate over the array, but there is
only one call site for this function (in tools/isobuild/package-source.js)
right now, so that wasn't too much work.
This includes https://github.com/laverdet/node-fibers/pull/429, fixing the
CPU spikes reported and discussed here: https://github.com/meteor/meteor/pull/10527#issuecomment-567982128
Using an official fibers release rather than a GitHub URL is preferable
because it doesn't require building fibers from source when deploying a
Meteor app to production, and also doesn't rely on GitHub being
operational, though of course it does rely on other networked services
like npm.
We haven't always updated this minimum version when we've changed the
Node.js version bundled with Meteor, which is fine because most deployment
strategies (including Galaxy) use the right version of Node.js
automatically. With Meteor 1.9 and Node.js 12.14.0, however, it seems
important that we make absolutely sure new Meteor apps are not getting run
in production with an end-of-life'd version of Node.js (v8).
Apparently calling v8::Isolate::AdjustAmountOfExternalAllocatedMemory
frequently results in lots of wasted CPU cycles on garbage collection, per
discussion here: meteor/meteor#10527 (comment)
This fix was inspired by marudor/libxmljs2#22, which seems to have
addressed nodejs/node#30995.
Another project that benefitted from adjusting external allocated memory
less often: mapnik/node-mapnik#136
With Node.js 8.x nearing end-of-life status at the end of this year, and
Node.js 12 now in LTS, we think it makes sense to finalize Meteor 1.9
sooner rather than later, and continue working to take advantage of all
the great features of Node 12 in future 1.9.x releases.
As usual, the meaning of "release candidate" is that we can still fix bugs
before the final release, but there will be no new features added.
When we run 'meteor test-packages' as part of our Circle CI test rotation,
we happen to be testing the Meteor `jquery` package along with all of our
other packages, so it has a chance to define `window.jQuery` globally, so
everything seems to work.
However, if you run `test-packages` with a subset of packages that does
not include or depend on `jquery`, there will be errors in the browser
console about `jQuery` not being defined, because the `test-in-browser`
package depends on `blaze`, which implicitly depends on `jquery`.
