No commonjs module resolution when there is no jsconfig.json

[egamma]

Extracted from microsoft/vscode#3509.

According to #6807 the default for module type is commonjs. However, in this example without a jsconfig.json then there are no completion proposals:

• no jsconfig.json
• add a file bar.js:

exports.foo = 3;

• add app.js add the following:

var bar = require('./bar');
bar.

There a no completions on bar.

The work around is to add a jsconfig.json that defines the module type to commonjs:

jsconfig.json

{
    "compilerOptions": {
        "module": "commonjs"
    }
}

[billti]

Pull request #7466 is out for this issue.