Add publish --dry_run to the cargo_test

Add trivial README.md files for this to pass.

This will catch some but not all issues with the crates that would cause them to be rejected by crates.io

PiperOrigin-RevId: 702766719

rust/release_crates/README.md

@@ -0,0 +1,4 @@
+This directory contains one directory per crate that we release.
+
+Each directory contains a pkg_tar() which packages up the crate into a tar which
+can be pushed to crates.io.

rust/release_crates/cargo_test.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
-# Runs tests that are defined in the protobuf crate using Cargo.
+# Runs tests that are defined in the protobuf crate using Cargo. This also
+# performs a publish dry-run, which catches some but not all issues that
+# would prevent the crates from being published.
 # This is not a hermetic task because Cargo will fetch the needed
 # dependencies from crates.io
 
@@ -59,9 +61,15 @@ tar -xvf $EXAMPLE_TAR -C $EXAMPLE_ROOT
 cd $CRATE_ROOT
 # Run all tests except doctests
 CARGO_HOME=$CARGO_HOME cargo test --lib --bins --tests
+CARGO_HOME=$CARGO_HOME cargo publish --dry-run
 
 cd $CODEGEN_ROOT
 CARGO_HOME=$CARGO_HOME cargo test --lib --bins --tests
+CARGO_HOME=$CARGO_HOME cargo publish --dry-run
 
 cd $EXAMPLE_ROOT
 CARGO_HOME=$CARGO_HOME cargo test
+# TODO: Cannot enable this dry-run yet because it checks that the versions of
+# its dependencies are published on crates.io, which they are definitely not
+# in this case.
+# CARGO_HOME=$CARGO_HOME cargo publish --dry-run

rust/release_crates/protobuf/BUILD

@@ -29,6 +29,7 @@ genrule(
 filegroup(
     name = "srcs",
     srcs = [
+        "README.md",
         "build.rs",
         ":gen_cargo_toml",
     ],

rust/release_crates/protobuf/README.md

@@ -0,0 +1 @@
+The runtime of the official Google Rust Protobuf implementation.

rust/release_crates/protobuf_codegen/BUILD

@@ -29,6 +29,7 @@ genrule(
 filegroup(
     name = "srcs",
     srcs = [
+        "README.md",
         ":gen_cargo_toml",
     ] + glob(["src/**/*"]),
     visibility = ["//rust:__subpackages__"],

rust/release_crates/protobuf_codegen/README.md

@@ -0,0 +1,2 @@
+The build time dependency crate for generating code for the Google Rust Protobuf
+implementation.

rust/release_crates/protobuf_example/README.md

@@ -0,0 +1,2 @@
+An example that demonstrates how to use the `protobuf` and `protobuf_codegen`
+crates together.