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https://github.com/mysticatea/import-cjs-issue
https://github.com/mysticatea/import-cjs-issue
Last synced: about 2 months ago
JSON representation
- Host: GitHub
- URL: https://github.com/mysticatea/import-cjs-issue
- Owner: mysticatea
- License: mit
- Created: 2019-10-02T06:24:38.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2019-10-02T07:48:10.000Z (over 5 years ago)
- Last Synced: 2024-05-02T06:14:42.799Z (8 months ago)
- Language: JavaScript
- Size: 3.91 KB
- Stars: 0
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# `import(cjs)` issue
With Node.js v12.11.1, On Windows 10,
## test.js
```
node --experimental-modules test.js
```
Source Code
```js
console.log("version:", process.version)
;(async () => {
console.log("==== ESM ====")
await import("x-esm") //→ Found as expected
await import("./node_modules/x-esm/index.js?q=0") //→ Found and `x-esm` re-ran as expected
await import("./node_modules/x-esm/index.js?q=1") //→ Found and `x-esm` re-ran as expected
console.log("==== CJS ====")
const cjs = await import("x-cjs") //→ Found as expected
const cjs0 = await import("./node_modules/x-cjs/index.js?q=0") //→ Found but `x-cjs` didn't re-run
const cjs1 = await import("./node_modules/x-cjs/index.js?q=1") //→ Found but `x-cjs` didn't re-run
console.log(cjs === cjs0, cjs === cjs1, cjs0 === cjs1) //→ all are false but `x-cjs` didn't run three times
console.log("---- remove 'require.cache' ----")
delete require.cache[require.resolve("x-cjs")]
await import("x-cjs") //→ Found but `x-cjs` didn't re-run
await import("./node_modules/x-cjs/index.js?q=0") //→ Found but `x-cjs` didn't re-run
await import("./node_modules/x-cjs/index.js?q=1") //→ Found but `x-cjs` didn't re-run
await import("./node_modules/x-cjs/index.js?q=2") //→ Found and `x-cjs` re-ran as expected
await import("./node_modules/x-cjs/index.js?q=3") //→ Found but `x-cjs` didn't re-run
})().catch(error => {
console.error(error)
process.exitCode = 1
})
```
Result
```
(node:14972) ExperimentalWarning: The ESM module loader is experimental.
version: v12.11.1
==== ESM ====
x-esm
x-esm
x-esm
==== CJS ====
x-cjs
false false false
---- remove 'require.cache' ----
x-cjs
```
### Description
I tried to import packages without import cache. From the document, it looks I should use query strings.
```js
await import("x-esm") //→ Found as expected
await import("./node_modules/x-esm/index.js?q=0") //→ Found and `x-esm` re-ran as expected
await import("./node_modules/x-esm/index.js?q=1") //→ Found and `x-esm` re-ran as expected
```
`x-esm` is an ES module package. It worked as expected.
```js
const cjs = await import("x-cjs") //→ Found as expected
const cjs0 = await import("./node_modules/x-cjs/index.js?q=0") //→ Found but `x-cjs` didn't re-run
const cjs1 = await import("./node_modules/x-cjs/index.js?q=1") //→ Found but `x-cjs` didn't re-run
console.log(cjs === cjs0, cjs === cjs1, cjs0 === cjs1) //→ all are false but `x-cjs` didn't run three times
```
`x-cjs` is a CJS package. The result was odd. The `console.log()` in `x-cjs` package ran only one time, but the returned values are different for each query string.
I found the entry of `x-cjs` in `require.cache`. However, the cache entry is odd as well. It's different from `require("x-cjs")`, the entry doesn't have `parent` property and the `module.children` of `test.js` is still empty.
Anyway, I tried to remove the cache entry.
```js
console.log("---- remove 'require.cache' ----")
delete require.cache[require.resolve("x-cjs")]
await import("x-cjs") //→ Found but `x-cjs` didn't re-run
await import("./node_modules/x-cjs/index.js?q=0") //→ Found but `x-cjs` didn't re-run
await import("./node_modules/x-cjs/index.js?q=1") //→ Found but `x-cjs` didn't re-run
await import("./node_modules/x-cjs/index.js?q=2") //→ Found and `x-cjs` re-ran as expected
await import("./node_modules/x-cjs/index.js?q=3") //→ Found but `x-cjs` didn't re-run
```
Cryptic. I guess this behavior is:
- `import(cjs)` has cache apart from `require.cache`.
- The `import(cjs)` cache is created from `require.cache`.
- It runs CJS package only if `require.cache` entry was not found.
- The `import(cjs)` cache is not removed even if `require.cache` entry deleted.
Therefore, I have to do the following steps if I want to import packages without cache.
1. Find the main file of the package because I cannot put query strings to the package name.
```js
const url = "file:" + require.resolve(packageName) + uniqueQueryString;
```
1. Import it.
```js
const ret = await import(url);
```
1. Delete `require.cache` entry.
```js
delete require.cache[require.resolve(packageName)];
```
### Questions
1. Is it intentional behavior that `import(cjs)` creates incomplete `require.cache` entries?
1. If yes, is it intentional behavior that `import(cjs)` with query strings returns different objects for the same CJS package?
I'm guessing that `import(cjs)` should not create any `require.cache` entries, and `import(cjs)` with query strings re-runs CJS packages as same as ES packages.