microsoft / microsoft/TypeScript
The module namespace object returned by __importStar is not the same when import the same module multiple times
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Description
### 🔎 Search Terms
- `__importStar`
- `module object`
- `namespace object`
### 🕗 Version & Regression Information
- Version: 6.0.2
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about "namespace import". I did not found any information related to this.
### ⏯ Playground Link
https://www.typescriptlang.org/play/?target=99&jsx=0&module=1&ts=6.0.2#code/DYUwLgBADgjBC8ECWBbKB7ATmAFAIgDMBnPASgG4BYAKFEigCYFk0tdCSKaaAFTdFEiIgAdAENgwHAG1YAGmgMAuqRFgAFiAB2OGcRgLiy0ggB8EAN40INiAGN0WoulAjg6AOY59CeIiMUEAD0QRBgmACuIDQAvlzUQA
### 💻 Code
```ts
let p1 = import("fs");
let p2 = import("fs");
Promise.all([p1, p2]).then(([fs1, fs2]) => {
console.log(fs1 === fs2); // expected true
});
```
### 🙁 Actual behavior
When the compiled code with node is run, `false` is printed. This means that the two imported module namespace object is different. each `__importStar` call create a new module namespace object.
### 🙂 Expected behavior
`true` should be printed. The module namespace objects of these two `import("fs")` should be the same object.
If we run this script directly by `node` without compiled, `true` will be printed.
### Additional information about the issue
To reproduce this issue, "module" in "tsconfig.json" need to be set to "commonjs". This makes `tsc` use `__importStar` and `require` to import the module.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the __importStar helper and the CommonJS module path described in the issue, using the linked Playground example and a Node.js run as the reproduction. Compare the two Promise results and trace how repeated import("fs") calls create namespace objects; done means the compiled CommonJS case matches direct Node.js behavior and returns the same object.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- node.js, typescript
- Domain
- build-system, compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 52/100