[0.20.4] URL missing single character with extra slash

[pe8ter]

Overview

Trying to load a simple script with a default .js extension but the URL is missing a character and has an extra slash. This did not happen in 0.20.3, but broke in 0.20.4. Here is my config:

SystemJS.config({
    packages: {
        '/': {
            defaultExtension: 'js',
        },
    },
});

And for completeness my import:

SystemJS.import('foo');

Expected result

The script foo.js should load and execute.

Actual result

The script fails to load with 400 (Bad Request):

GET http://localhost:3000//oo.js 400 (Bad Request)
N @ fetch.js:32
(anonymous) @ instantiate.js:165
Uncaught (in promise) Error: Fetch error: 400 Bad Request
  Instantiating http://localhost:3000//oo.js
  Loading /foo.js
    at fetch.js:37
t @ common.js:83
(anonymous) @ loader-polyfill.js:70

Apologies for the noisy error dump, but you can at least see the mangled URL.

[pe8ter]

I found the change between 0.20.3 and 0.20.4 that is the root of the issue. In config.js there is a line to create a variable pkgName. You can see here that the variable gets assigned then used. In the previous version there was one more line to cut off the trailing slash.

Now that the package name keeps the trailing slash when we get to finding the sub-path from the normalized URL, packageKey is too long so one extra character from the sub-path gets removed. The sub-path for http://localhost:3000/foo becomes oo instead of foo and thus the errors above.

[guybedford]

@pe8ter thanks I've added this fix as you suggest in 647ccef.

[guybedford]

Released in 0.20.5

[pe8ter]

Thanks!