elm-make 0.16 creates index.html by default

[savuori]

Using a command elm-make Module.elm used to create only elm.js -file, now it creates an index.html file. If this is intentional it might be worth a mention in the upgrade guide because it causes tools like emacs' compile buffer have new side-effects, like overwriting the index.html.

[doppioslash]

also, how do we compile a stand-alone js file now? --output=file.js doesn't work.

[igrep]

Well, I experienced both cases in 0.16.
According to my experience, it creates elm.js in newly created elm project,
but it creates index.html in some existing projects.
It might be caused when index.html is already created.

[twitchard]

This behavior should be removed. It clobbered my existing index.html and made me lose work. Very off-putting to newbies like me.

[evancz]

This change was made to accommodate new folks. If someone new to Elm is using elm-make they probably just want the HTML to be set up for them. If they decide the want ports, they will have found docs that explain how to do that with an --output flag.

That is the rationale. I get that there are tradeoffs, but this seems like "the best compromise" for now. Perhaps it makes sense to call it something besides index.html but also kind of doesn't make sense.

[twitchard]

@evancz
I propose the following: suppose elm-make includes an HTML comment somewhere in its output, indicating the file was generated with elm-make. Then, when elm-make detects that it is about to overwrite a file, it checks for that comment. If the comment is present, it overwrites the file without another thought. Otherwise, it warns the user it is going to overwrite a file and prompts for confirmation.