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module: cache synchronous module jobs before linking #52868

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6ea1c51
test: add common.expectRequiredModule()
joyeecheung May 7, 2024
0f4b120
module: cache synchronous module jobs before linking
joyeecheung May 7, 2024
c034992
fixup! module: cache synchronous module jobs before linking
joyeecheung May 7, 2024
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module: cache synchronous module jobs before linking 
So that if there are circular dependencies in the synchronous
module graph, they could be resolved using the cached jobs.
In case linking fails and the error gets caught, reset the
cache right after linking. If it succeeds, the caller will
cache it again. Otherwise the error bubbles up to users,
and since we unset the cache for the unlinkable module
the next attempt would still fail.
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@joyeecheung
joyeecheung committed May 7, 2024
commit 0f4b1200cbc789e8e5081b5d9c62056740afa6e7
39 changes: 25 additions & 14 deletions lib/internal/modules/esm/module_job.js
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Expand Up @@ -295,22 +295,33 @@ class ModuleJobSync extends ModuleJobBase {
#loader = null;
constructor(loader, url, importAttributes, moduleWrap, isMain, inspectBrk) {
super(url, importAttributes, moduleWrap, isMain, inspectBrk, true);
assert(this.module instanceof ModuleWrap);
this.#loader = loader;
const moduleRequests = this.module.getModuleRequests();
// Specifiers should be aligned with the moduleRequests array in order.
const specifiers = Array(moduleRequests.length);
const modules = Array(moduleRequests.length);
const jobs = Array(moduleRequests.length);
for (let i = 0; i < moduleRequests.length; ++i) {
const { specifier, attributes } = moduleRequests[i];
const job = this.#loader.getModuleJobForRequire(specifier, url, attributes);
specifiers[i] = specifier;
modules[i] = job.module;
jobs[i] = job;

assert(this.module instanceof ModuleWrap);
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// Store itself into the cache first before linking in case there are circular
// references in the linking.
loader.loadCache.set(url, importAttributes.type, this);
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@legendecas legendecas May 8, 2024

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Setting in cache at

node/lib/internal/modules/esm/loader.js

Lines 405 to 407 in fe4e569

job = new ModuleJobSync(this, url, importAttributes, wrap, isMain, inspectBrk);
this.loadCache.set(url, importAttributes.type, job);
would be redundant but I think it could be a follow up work.

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@joyeecheung joyeecheung May 8, 2024 •
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That was what I did initially but it would cache modules that failed to link and if that’s caught, subsequent attempts would not fail as expected - which is why I added comments explaining why it’s reset in the finally block (doing it inside the linking phase prevents a rethrow in the caller which looks less nice)

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@legendecas legendecas May 8, 2024 •
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Hmmm, maybe we could transform the try-finally into a try-catch-rethrow and only delete in catch? In this way we don't need to set cache again in the caller.

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@joyeecheung joyeecheung May 10, 2024 •
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The rethrow was exactly what I am trying to prevent - setting the cache again is fine as the overhead is trivial but having to rethrow in all callers of this makes the code harder to read IMO. It also makes all the source lines of the errors less readable, which shows in the stderr when they are not caught.


try {
const moduleRequests = this.module.getModuleRequests();
// Specifiers should be aligned with the moduleRequests array in order.
const specifiers = Array(moduleRequests.length);
const modules = Array(moduleRequests.length);
const jobs = Array(moduleRequests.length);
for (let i = 0; i < moduleRequests.length; ++i) {
const { specifier, attributes } = moduleRequests[i];
const job = this.#loader.getModuleJobForRequire(specifier, url, attributes);
specifiers[i] = specifier;
modules[i] = job.module;
jobs[i] = job;
}
this.module.link(specifiers, modules);
this.linked = jobs;
} finally {
// Restore it - if it succeeds, we'll reset in the caller; Otherwise it's
// not cached and if the error is caught, subsequent attempt would still fail.
loader.loadCache.delete(url, importAttributes.type);
}
this.module.link(specifiers, modules);
this.linked = jobs;
}

get modulePromise() {
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6 changes: 6 additions & 0 deletions lib/internal/modules/esm/module_map.js
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Expand Up @@ -114,6 +114,12 @@ class LoadCache extends SafeMap {
validateString(type, 'type');
return super.get(url)?.[type] !== undefined;
}
delete(url, type = kImplicitAssertType) {
const cached = super.get(url);
if (cached) {
cached[type] = undefined;
}
}
}

module.exports = {
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8 changes: 8 additions & 0 deletions test/es-module/test-require-module-cycle-cjs-esm-esm.js
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@@ -0,0 +1,8 @@
// Flags: --experimental-require-module
'use strict';

// This tests that ESM <-> ESM cycle is allowed in a require()-d graph.
const common = require('../common');
const cycle = require('../fixtures/es-modules/cjs-esm-esm-cycle/c.cjs');

common.expectRequiredModule(cycle, { b: 5 });
2 changes: 2 additions & 0 deletions test/fixtures/es-modules/cjs-esm-esm-cycle/a.mjs
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@@ -0,0 +1,2 @@
export { b } from './b.mjs';

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2 changes: 2 additions & 0 deletions test/fixtures/es-modules/cjs-esm-esm-cycle/b.mjs
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@@ -0,0 +1,2 @@
import './a.mjs'
export const b = 5;
1 change: 1 addition & 0 deletions test/fixtures/es-modules/cjs-esm-esm-cycle/c.cjs
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@@ -0,0 +1 @@
module.exports = require('./a.mjs');