Warn on top-level this

[Rich-Harris]

See #759 (comment)

[timdp]

I like this feature but without context, it's a bit scary. Maybe it could also log module.id, node.start, node.end, etc.?

[whaaaley]

I'm getting this warning when I'm importing certain modules from lodash-es could this be a false positive? map, sortBy, filter, clone are the ones triggering this for me in my project. Everything seems to be working fine though and there's also no mention of undefined in the output. Is this normal?

[jdalton]

From lodash/_root:

/** Detect `this` as the global object. */
var thisGlobal = checkGlobal(typeof this == 'object' && this);

[AgronKabashi]

I'm receiving a lot of these warnings (~20-30 times) when importing Angular 2 packages. I could suppress these messages by supplying the rollup config with my own onwarncallback but would that be considered good practice?

[TrySound]

@AgronKabashi There's context option.

[code-tree]

@TrySound Could you please elaborate in the case of Angular2, as I don't yet fully understand what's going on.

Is Angular2 doing something wrong here? If I set context: 'window' is the problem solved?

(ngc is generating the code that causes this warning, so I don't know what is going on under the hood)

[AgronKabashi]

@code-tree Yes, setting context: 'window' or context: 'this' will hide those messages.