Make crates-io registry URL optional in config; ignore all changes to source.crates-io

[carols10cents]

Hi! When I was working on the instructions for source replacement in this crates.io PR, I found that when I'm replacing source.crates-io, I still have to specify some value for registry, or else I get this:

error: no source URL specified for `source.crates-io`, need either `registry` or `local-registry` defined

This seems weird and annoying to me: cargo definitely knows the registry URL for crates-io, and I'm trying to replace it anyway.

So the first commit in this PR makes it optional, so that you don't have to specify a registry url for crates-io: it uses SourceId::crates_io, like it would if we didn't have any source configs at all.

The second commit in this PR might go too far, and/or might break existing uses of cargo, I'm not sure. In my opinion, source.crates-io should only be able to be replaced and never changed directly-- crates-io should always be crates-io, and I should be able to assume that in any project. So the second commit ignores all modifications to source.crates-io's registry, local-registry, and directory, and warns that they're being ignored.

I tried to search github to see if anyone was using these keys with source.crates-io, but since github's search ignores . (ARE YOU LISTENING GITHUB? I WOULD LIKE TO SEARCH WITH PUNCTUATION PLEASE), there's a lot of false positives to wade through. I didn't see anything in the first few pages though.

I'm happy to make whatever modifications to this!

[rust-highfive]

r? @alexcrichton

(rust_highfive has picked a reviewer for you, use r? to override)

[alexcrichton]

Thanks for the PR! This looks good to me, but perhaps we can hold off on enabling the warnings just yet? Now that support for custom registries is on beta (I think) we may want to wait for this to hit stable, update cargo vendor and cargo local-registry tools, and then turn on the warnings?

[carols10cents]

Thanks for the PR! This looks good to me, but perhaps we can hold off on enabling the warnings just yet? Now that support for custom registries is on beta (I think) we may want to wait for this to hit stable, update cargo vendor and cargo local-registry tools, and then turn on the warnings?

Sounds good! I've removed the 2nd commit but I've got it on a branch for later resubmission.

[alexcrichton]

Hm this'll still cause existing configurations to start failing though, right? That is, they'll start interpreting as having two sources configured which is an error?

Put another way, the test changes shouldn't be required here, just enough to make warnings go away.

[carols10cents]

Hm this'll still cause existing configurations to start failing though, right? That is, they'll start interpreting as having two sources configured which is an error?

Put another way, the test changes shouldn't be required here, just enough to make warnings go away.

I don't think this change will break existing configurations-- Cargo's current behavior is to silently ignore changes to crates.io's registry URL (but it requires you to specify a registry URL value, which is the problem I'm trying to solve because I shouldn't have to specify something that gets ignored anyway).

The test changes are not required. I've backed them out and the tests still pass, and instead I've added a new test to show that crates.io's registry URL being missing when replacing the source is no longer an error, which is the only behavior I'm intending this commit to change. This PR should have nothing to do with warnings anymore.

Am I missing something?

[alexcrichton]

Oh oops! I read this condition:

if name == "crates-io" && srcs.is_empty()

and missed the second clause of src.is_empty(). If you always pushed that'd be an error w/ today, but with that there's no error at all! Sorry for the runaround!

@bors: r+

[bors]

📌 Commit 2490f3f has been approved by alexcrichton

[bors]

⌛ Testing commit 2490f3f with merge 26dcd3e...

[bors]

☀️ Test successful - cargo-cross-linux, cargo-linux-32, cargo-linux-64, cargo-mac-32, cargo-mac-64, cargo-win-gnu-32, cargo-win-gnu-64, cargo-win-msvc-32, cargo-win-msvc-64
Approved by: alexcrichton
Pushing 26dcd3e to master...

[carols10cents]

Hooray!!!! Thank you :) <3 <3 <3