Since Meteor 1.9.2 included a rebuilt dev bundle, it's important to
rebuild the dev bundle again after merging master (which now corresponds
to 1.9.2) into devel (which has seen a number of dev bundle-relevant
changes that are not yet on master, e.g. MongoDB 4.0.6 => 4.2.1).
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.
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.
CircleCI tests will fail for this commit, since these changes do not
address the problem that the module.useNode() stub imports the ESM code
using require. I will fix the tests properly in a later commit.
