repl returns the result 'use strict' unexpectedly

[mikedmcfarland]

The result of some single undefined statements when using the repl via babel-node is 'use strict' when I'd expect it to be undefined.
For example, using node's repl produces:

> node
> var s = ""
undefined

While babel's repl produces:

> babel-node
> var s = ""
'use strict'

I'd expect the result of the expression to also be undefined.

in case it's relevant, my versions are:

> node --version
v0.12.7

> babel --version
5.8.23 (babel-core 5.8.23)

[bradencanderson]

Repro with babel-node -e "var a = 2;" -p.

This feels like a bug in the strict transformer. Consistent output between node and babel-node seems like a reasonable thing to expect.

babel-node -p should print the result of the source program, regardless of what the source is transformed into.

[loganfsmyth]

Consistent output between node and babel-node seems like a reasonable thing to expect.

This is actually the same as what node prints, if you include it all on one line.

> "use strict"; var a = 2;
'use strict'
> 

This doesn't have anything to do with the strict transformer specifically, what this essentially comes down to is some weirdness in the way eval works, e.g.

eval('"use strict"; var a = 2;') === 'use strict'; 

Seems like you'd want a plugin to automatically add an expressionStatement to the end of the code if there wasn't one (assuming that is the logic eval follows).

Program(node){
    if (!t.isExpressionStatement(node.body[node.body.length - 1)){
        node.body.push(t.expressionStatement(t.identifier('undefined')));
    }
}

[jamiebuilds]

@loganfsmyth That seems to be okay, I would just be worried about an edge case where the actual result isn't being output because undefined was being pushed to the end.

[hzoo]

I believe we did this in #4562