This package provides a ponyfill for the ModuleSource
constructor, suitable
for use in the SES shim's module descriptors.
The module source accepts a JavaScript module and converts it into
a form that SES can use to emulate and confine JavaScript modules (ESMs, the
mjs
file format) with compartments.
import 'ses';
import { ModuleSource } from '@endo/module-source';
const c1 = new Compartment({}, {}, {
name: "first compartment",
resolveHook: (moduleSpecifier, moduleReferrer) => {
return resolve(moduleSpecifier, moduleReferrer);
},
importHook: async moduleSpecifier => {
const moduleLocation = locate(moduleSpecifier);
const moduleText = await retrieve(moduleLocation);
return new ModuleSource(moduleText, moduleLocation);
},
});
The ModuleSource
is a shim for what we hope to eventually call a native
ModuleSource
constructor.
However, in the absence of a native ModuleSource
, this produces a
serializable object that emulates the behavior of ModuleSource
in conjunction
with the Compartment
constructor from ses
.
A detail that leaks from the implementation is that the constructor rewrites
the source, from an ESM [[Module]]
grammar construction to a [[Program]]
construction suitable for confining with the compartment's confined evaluator.
This transform attempts to be unobtrusive, but currently causes some alignment changes due to (hopefully temporary) limitations to the underlying code generator. In the interim, generating a source map can help.
The ModuleSource
constructor accepts non-standards-track
sourceMapHook
and sourceMapUrl
options.
Previously, the sole option was a string
argument for the sourceUrl
, such
that this would be appended to the generated source.
This change allows for the old or new usage:
new ModuleSource(source, sourceUrl);
// or
new ModuleSource(source, { sourceUrl, sourceMapUrl, sourceMapHook });
The sourceMapUrl
is necessary for generating a source map.
The URL will appear only in the generated source map, so a fully qualified
source map URL is safe and allows for continuity if the map is generated and
debugged on the same host.
This is important because Endo captures precompiled Static Module Records in
bundles, excluding source maps, such that a relative path is not useful.
The sourceMapHook
will receive a string source map and a details bag
including:
source
sourceUrl
sourceMapUrl
Such that the receiver can store the source map somewhere as a side-effect.
Note: the sourceMapHook
is synchronous and returns void
.
Exceptions thrown by the hook will propagate up through the constructor. If
the hook returns a promise, it will be dropped and rejections will go uncaught.
If the hook must do async work, these should be queued up as a job that the
caller can later await.
With the xs
condition, @endo/module-source
will not entrain Babel and will
just adapt the native ModuleSource
to the older interface presented by this
package.
That is, the XS native bindings
will be translated to imports
, exports
,
and reexports
getters.
This form of ModuleSource
ignores all options.
Please help us practice coordinated security bug disclosure, by using the instructions in SECURITY.md to report security-sensitive bugs privately.
For non-security bugs, please use the regular Issues page.