https://github.com/lddubeau/systemjs_issue3
Reproduction of a problem with SystemJS
https://github.com/lddubeau/systemjs_issue3
Last synced: 16 days ago
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Reproduction of a problem with SystemJS
- Host: GitHub
- URL: https://github.com/lddubeau/systemjs_issue3
- Owner: lddubeau
- Created: 2017-03-30T17:38:44.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2017-03-30T17:51:02.000Z (about 8 years ago)
- Last Synced: 2025-02-17T15:51:56.856Z (3 months ago)
- Language: JavaScript
- Size: 2.93 KB
- Stars: 0
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
### Versions
I get the problem with versions 0.20.0 to 0.20.11.
I was not able to reproduce it with any version in the 0.19 series.
### Symptoms
I get a big fat exception:
```
Error: Cannot read property '0' of undefined
```
Which points to [this](https://github.com/systemjs/systemjs/blob/0.20.10/dist/system.src.js#L1029). It is the `var depLoad = dependencyInstantiations[i];` line in the following code:
```
function makeDynamicRequire (loader, key, dependencies, dependencyInstantiations, registry, state, seen) {
// we can only require from already-known dependencies
return function (name) {
for (var i = 0; i < dependencies.length; i++) {
if (dependencies[i] === name) {
var depLoad = dependencyInstantiations[i];
var module;
if (depLoad instanceof ModuleNamespace)
module = depLoad;
```
When I add tracing to the console, I find that `makeDynamicRequire` is sometimes called with a `dependencies` array which has a length > 0 but with `dependencyInstantiations` that is undefined.
### How to reproduce the problem
Clone https://github.com/lddubeau/systemjs_issue3
1. ``npm install``.
2. Start the server ``./server.js localhost:[some port number]``. **It
is important that you use THIS SERVER. The problem here is a race
condition, and the server purposely delays responding to the request
for one module so as to recreate the conditions necessary for the
problem to occur.**
3. Direct your browser to load ``http://localhost:[same port number]/index.html``.
If you are lucky, you'll immediately get:
```
Uncaught (in promise) Error: Cannot read property '0' of undefined
Loading x
at register-loader.js:532
at doEvaluate (register-loader.js:607)
at ensureEvaluate (register-loader.js:518)
at register-loader.js:538
at doEvaluate (register-loader.js:607)
at ensureEvaluate (register-loader.js:518)
at register-loader.js:538
at doEvaluate (register-loader.js:607)
at ensureEvaluate (register-loader.js:518)
at register-loader.js:538
```
If you are unlucky, you may need to reload until you get the error, or
it might require that you play with the timeout that is set in
index.html.
When I try it here I get the error nearly 100% of the time.