[ssr] Improve module loader and add a module cache that track imports. #2288
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| const modulePromise = (async () => { | ||
| const source = await fs.readFile(modulePath, 'utf-8'); | ||
| // TODO: store and re-use cachedData: |
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Comment still relevant? It is cached now, right? Or if there's another layer of caching we could do, maybe elaborate on the comment (there is nothing called cachedData).
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This is referring to Node's vm module cachedData, which should speed up repeated module creation in cases where we create fresh vm contexts. It's not related to our module cache. I updated the link and it seems like they added cachedData for modules now, so we can do this.
| ) { | ||
| // Override where we resolve lit-html from so that we always resolve to | ||
| // a single version of lit-html. | ||
| referrer = import.meta.url; |
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Does this force one version because it causes us to resolve relative to the top-level node_modules directory instead of a nested one?
What if there are two conflicting versions of Lit?
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Yes.
We have a bit of work to do here to test behavior with multiple versions of Lit. Since Lit 2.0 we don't require instanceof anymore, so we might not even need this. It wouldn't be used in the "global" mode (where we path Node's global and don't load modules like this) anyway, but I don't want to change this quite yet.
| // in their package.json to differentiate their ES module version. | ||
| packageFilter: (packageJson: PackageJSON) => { | ||
| packageJson.main = | ||
| packageJson.module ?? packageJson['jsnext:main'] ?? packageJson.main!; |
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I think ?? index.js should be the final fallback?
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resolve should already implement that then. Here we're just adding in some non-standard behavior to look at the module and jsnext:main fields.
| referrer = import.meta.url; | ||
| } | ||
| const referencingModulePath = new URL(referrer).pathname; | ||
| const modulePath = resolve.sync(specifier, { |
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Will this handle package exports?
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I don't know... I don't think this package has been updated in a while.
| packages/labs/ssr/lib/ | ||
| packages/labs/ssr/node_modules/ | ||
| packages/labs/ssr/test/ | ||
| packages/labs/ssr/test/**/*.js |
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Are these changes needed? Maybe they belong in another PR that adds tests? Same for .prettierignore.
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This PR does add tests. Some of your comments were on older version files though, so maybe you didn't see them?
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Oops yeah I missed them somehow.
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@aomarks PTAL |
This make the module loader a class so that it can hold instance state about the cache, current vmContextID. This way more than one loader could be instantiated, which would be important for hosting multiple apps. This is working towards being able to introspect and modify the module cache too.