Odd file completion for file in subdirectory returned when using compilerOptions.path

[mjbvz]

TypeScript Version: 2.7.1

Search Terms:

• Path intellisense
• Path completions

Code

$ git clone https://github.com/mjbvz/ts-issue-21582

1. For a js project:

jsconfig.json
src/
  index.js
  keeper.js
  animals/
      cat.js

With jsconfig.json:

{
	"compilerOptions": {
		"module": "commonjs",
		"target": "es2016",
		"baseUrl": ".",
		"paths": {
			"@zoo/*": ["./src/*"]
		}
	},
	"exclude": [
		"node_modules",
		"**/node_modules/*"
	]
}

2. In src/index.js, type: import {} from '@zoo/animals/'

3. Trigger path intellisense after @zoo/animals/

Expected behavior:
Returns a file completion for `cat.

Actual behavior:
An odd completion for /cat is returned:

[Trace  - 2:30:56 PM] Response received: completions (470). Request took 4 ms. Success: true 
Result: [
    {
        "name": "/cat",
        "kind": "external module name",
        "kindModifiers": "",
        "sortText": "/cat",
        "replacementSpan": {
            "start": {
                "line": 1,
                "offset": 30
            },
            "end": {
                "line": 1,
                "offset": 30
            }
        }
    }
]

This causes the import to become '@zoo/animals//cat'

Related:
#21589
#21591