tools/proto-compiler output does not compile on current master

[hdevalence]

Steps to reproduce

1. Check out a clean copy of tendermint-rs
2. Run cargo test; it succeeds
3. cd tools/proto-compiler && cargo run && cd ../..; succeeds
4. cargo test fails, as the output no longer compiles:

/t/tendermint-rs (master|✚4) $ cargo test
   Compiling tendermint-proto v0.23.0 (/private/tmp/tendermint-rs/proto)
error[E0433]: failed to resolve: use of undeclared type `Vec`
   --> proto/src/prost/tendermint.abci.rs:239:35
    |
239 |     #[serde(skip_serializing_if = "Vec::is_empty", with = "serde_bytes")]
    |                                   ^^^^^^^^^^^^^^^ not found in this scope
    |
help: consider importing one of these items
    |
9   | use alloc::vec::Vec;
    |
9   | use crate::Vec;
    |
9   | use serde::__private::Vec;
    |

For more information about this error, try `rustc --explain E0433`.
error: could not compile `tendermint-proto` due to previous error
warning: build failed, waiting for other jobs to finish...
error: build failed

My best guess is that this is a no_std-related issue but I don't actually know.

What's the definition of "done" for this issue?

• fix proto-compiler to produce working code;
• add some kind of check to CI that actually exercises the codepaths?

[hdevalence]

I think this can be fixed as follows:

diff --git a/proto/src/prost/tendermint.abci.rs b/proto/src/prost/tendermint.abci.rs
index c34e6d1b..4e514228 100644
--- a/proto/src/prost/tendermint.abci.rs
+++ b/proto/src/prost/tendermint.abci.rs
@@ -236,7 +236,7 @@ pub struct ResponseInfo {
     #[serde(with = "crate::serializers::from_str")]
     pub last_block_height: i64,
     #[prost(bytes="vec", tag="5")]
-    #[serde(skip_serializing_if = "Vec::is_empty", with = "serde_bytes")]
+    #[serde(skip_serializing_if = "::prost::alloc::vec::Vec::is_empty", with = "serde_bytes")]
     pub last_block_app_hash: ::prost::alloc::vec::Vec<u8>,
 }
 /// nondeterministic

[thanethomson]

I can successfully reproduce this. Seem as though it may have something to do with this line that gets removed when I re-run proto-compiler:

tendermint-rs/proto/src/tendermint.rs

Line 56 in 858b577

use crate::prelude::*;

I'll have to look into why it's removing that line though.

[thanethomson]

Oh it's probably because that line was added manually 😄 Damn. I'll look into fixing this.