[ci] fully qualify --package IDs in toolchain roller, cargo.sh (#1568)

By doing so, we prevent CI from being blocked by our dev-dependencies
taking dependencies on earlier versions of zerocopy. Such a scenario
introduces multiple packages named "zerocopy" and "zerocopy-derive"
into the build, and, consequently, `-p zerocopy` and
`-p zerocopy-derive` become ambiguous in most contexts.

.github/workflows/roll-pinned-toolchain-versions.yml

@@ -92,12 +92,22 @@ jobs:
             # introduced on this new toolchain that we can fix automatically.
             # This is best-effort, so we don't let failure cause the whole job
             # to fail.
-            cargo "+$VERSION_FOR_CARGO" fix --allow-dirty --tests --package zerocopy $ZEROCOPY_FEATURES || true
-            cargo "+$VERSION_FOR_CARGO" fix --allow-dirty --tests --package zerocopy-derive             || true
+            #
+            # We use `cargo pkgid` here to ensure that the package identifier is
+            # fully qualified. Otherwise, if a dev-dependency were to take a
+            # dependency on an earlier version of zerocopy or zerocopy-derive,
+            # these invocations would fail due to ambiguity.
+            cargo "+$VERSION_FOR_CARGO" fix --allow-dirty --tests --package "$(cargo pkgid -p zerocopy)" $ZEROCOPY_FEATURES || true
+            cargo "+$VERSION_FOR_CARGO" fix --allow-dirty --tests --package "$(cargo pkgid -p zerocopy-derive)"            || true
 
             # Update `.stderr` files as needed for the new version.
-            TRYBUILD=overwrite cargo "+$VERSION_FOR_CARGO" test --package zerocopy $ZEROCOPY_FEATURES
-            TRYBUILD=overwrite cargo "+$VERSION_FOR_CARGO" test --package zerocopy-derive
+            #
+            # We use `cargo pkgid` here to ensure that the package identifier is
+            # fully qualified. Otherwise, if a dev-dependency were to take a
+            # dependency on an earlier version of zerocopy or zerocopy-derive,
+            # these invocations would fail due to ambiguity.
+            TRYBUILD=overwrite cargo "+$VERSION_FOR_CARGO" test --package "$(cargo pkgid -p zerocopy)" $ZEROCOPY_FEATURES
+            TRYBUILD=overwrite cargo "+$VERSION_FOR_CARGO" test --package "$(cargo pkgid -p zerocopy-derive)"
           }
 
           if [ "${{ matrix.toolchain }}" == stable ]; then

tools/cargo-zerocopy/src/main.rs

@@ -231,9 +231,46 @@ fn delegate_cargo() -> Result<(), Error> {
                     get_toolchain_rustflags(name),
                     env_rustflags,
                 );
-                rustup(["run", version, "cargo"], Some(("RUSTFLAGS", &rustflags)))
-                    .args(args)
-                    .execute();
+
+                let mut cmd = rustup(["run", version, "cargo"], Some(("RUSTFLAGS", &rustflags)));
+
+                // Computes the fully-qualified package name of workspace package `p`.
+                let fqpn = |p| {
+                    // Generate a lockfile, if absent.
+                    // This is a prerequisite of running pkgid.
+                    let _ = rustup(["run", version, "cargo", "generate-lockfile"], None)
+                        .output_or_exit();
+
+                    let output = rustup(["run", version, "cargo", "pkgid", "-p"], None)
+                        .arg(p)
+                        .output_or_exit();
+                    String::from_utf8(output.stdout).unwrap()
+                };
+
+                // Replace `-p<package>`, `-p <package>` and `--package <package`
+                // with the equivalent of `-p $(cargo pkgid -p <package>)`. We do
+                // this because unqualified package names are sometimes ambiguous
+                // if a dev-dependency has taken a dependency on an earlier
+                // version of zerocopy or zerocopy-derive.
+                loop {
+                    let Some(arg) = args.next() else {
+                        break;
+                    };
+                    if arg == "-p" || arg == "--package" {
+                        cmd.arg(arg);
+                        let Some(arg) = args.next() else {
+                            break;
+                        };
+                        cmd.arg(fqpn(arg));
+                    } else if arg.starts_with("-p") {
+                        cmd.arg("-p");
+                        cmd.arg(fqpn(arg[2..].to_string()));
+                    } else {
+                        cmd.arg(arg);
+                    }
+                }
+
+                cmd.execute();
 
                 Ok(())
             } else {