Make #[serde(alias)] works in #[serde(flatten)] context

[bebecue]

fix #1504

[oli-obk]

Please also add a few tests for a struct like the one from the issue.

[bebecue]

Please also add a few tests for a struct like the one from the issue.

Added in 01da3f7

[dtolnay]

Thanks!

In #2160 (review) I was hopeful that somebody would look into what possibility of breakage this has for existing formats, but in the absence of anyone having been willing to do that, I think it will be all right to reassess based on any reported consequences.

[janik-cloudflare]

Thanks a ton @bebecue, @dtolnay and everyone else! Just ran into this and it's fantastic to see that a fix is already out. Really appreciate your work on serde :)

[banool]

I was hopeful that somebody would look into what possibility of breakage this has for existing formats, but in the absence of anyone having been willing to do that, I think it will be all right to reassess based on any reported consequences.

I know I'm well and truly late to the party hahah but this change did break some of our code.

At a high level you can see the issue like this:

git clone git@github.com:aptos-labs/aptos-core.git
# Change serde version in Cargo.toml to 1.0.153
cd testsuite/generate-format
cargo run -- --corpus aptos

With 1.0.152 this code works without error.

I tried the latest version of serde (1.0.188 at the time of writing) and the issue seems to persist.

I'm still trying to figure out how this change actually breaks our code, I just wanted to report in with an instance of a breakage. Once I know precisely what it changes for us I'll chime in again, though this looks pretty complicated.

[banool]

btw I looked into some issues in this repo. I know serde complies with semver but I also know that that only applies to public APIs, so I'm not 100% sure if this qualifies as a breaking change. I'll try figure that out and open a new issue if so.

[banool]

Moving to this issue now: #2627.