Indicate compilation progress in a form useful to end users

[kmcallister]

Was #22227, closed due to vandalism.

@sanxiyn said:

I think we should have --progress option. This could show phases, and for long phases like type checking, this could even show the name of the function being checked.

To which I replied:

+1. We can use control codes to update parts of the terminal without spewing output.

I will think about how to integrate this with --color and the drawing characters.
I'm imagining that rustc in whiz-bang fancy terminal mode would display progress on a single line, updated at each stage:

[/] Parsing
[-] Expanding macros
[\] Resolving names
[|] Checking types
[/] Checking lifetimes
[-] Checking
[+] All checks passed; generating LLVM
[+] All checks passed; optimizing
[+] All checks passed; generating machine code
[+] All checks passed; linking
[+] Compilation successful (in 0m 18s)
your-prompt$

And just that last "success" message will remain in your terminal buffer.

The spinner has a constant speed in wall-clock terms. Long-running parts of rustc will call sess.update_spinner() now and then to keep it going.

After we pass the "rest easy" point, the spinner turns into a calming + and the first part of the message turns green.

[blaenk]

Yes this would be so cool.

[asolove]

I'm brand new to contributing, but I'd like to take a crack at this one. I'm pretty sure I can do the pretty terminal bits, but I would probably need help keeping the spinner running.

[asolove]

I don't understand the relationship between the term repo and the libterm folder in this repo. But over in the term repo, I am working on an already-extant issue to add more features to the Terminal interface. Presumably if that lands there, it could get merged in here and be available for this PR.

[blaenk]

I'm not so sure myself, but my understanding is that since rustc doesn't use cargo, they embed the crate directly into this source tree.

[asolove]

Quick update: the needed terminal stuff landed in the standalone term crate, but there is some work needed to get the version in libterm here to match that, because the term crate now uses winapi bindings that aren't yet available here. I don't fully understand how to make that happen, and if adding all that stuff to this repo is worth it over this little progress animation.

In the mean time, I also started working on the substance of this issue in my progress branch. I think I can finish off the pretty-printing stuff, but I will still need helping figuring out how to get the spinner animation to work while other long-running compile phases are going on.

[retep998]

@asolove You should be able to just add the required definitions to the liblibc in here.

[dcampbell24]

What happens when things other than the progress notifications are printed to the screen? I like how apt-get handles this. The bottom line displays progress while all the other output gets printed above it.

[|] Checking

warning: this is a warning
[/] Checking

warning: this is a warning
warning: some other warning
[-] Checking

warning: this is a warning
warning: some other warning
another message from rustc
[\] Checking

[asolove]

@dcampbell24 Yup, that's how this will work too. I think the practical way to get that behavior is to print out and then do a carriage return to move back to the beginning of the line you just printed to. Other output will overwrite it and add a newline and then we'll print the next status update to the bottom of the output.