Add integration test for external relative path deps (issue #3089)

This test reproduces the bug where crate_universe fails when a Cargo
workspace member has a path dependency pointing outside the Cargo
workspace root (but still inside the Bazel workspace).

The test is expected to fail until the bug is fixed.

Author: criemen

.bazelci/presubmit.yml

@@ -637,6 +637,12 @@ tasks:
     build_targets:
       - "@rust_toolchains//:all"
       - "//..."
+  external_relative_path_deps:
+    name: External relative path deps (issue 3089)
+    platform: ubuntu2204
+    working_directory: test/integration/external_relative_path_deps
+    build_targets:
+      - "//..."
   android_examples_ubuntu2204:
     name: Android Examples
     platform: ubuntu2204

test/integration/external_relative_path_deps/.bazelversion

@@ -0,0 +1 @@
+8.0.0

test/integration/external_relative_path_deps/.gitignore

@@ -0,0 +1 @@
+/bazel-*

test/integration/external_relative_path_deps/BUILD.bazel

@@ -0,0 +1 @@
+# Empty BUILD file for workspace root

test/integration/external_relative_path_deps/MODULE.bazel

@@ -0,0 +1,38 @@
+"""Test for external relative path dependencies (issue #3089)"""
+
+module(
+    name = "external_relative_path_deps_test",
+    version = "0.0.0",
+)
+
+bazel_dep(name = "rules_rust", version = "0.0.0")
+local_path_override(
+    module_name = "rules_rust",
+    path = "../../..",
+)
+
+rust = use_extension("@rules_rust//rust:extensions.bzl", "rust")
+rust.toolchain(edition = "2021")
+use_repo(rust, "rust_toolchains")
+
+register_toolchains("@rust_toolchains//:all")
+
+# Test: crate_universe with Cargo workspace where a member has a path dependency
+# that goes OUTSIDE the Cargo workspace root (but still inside the Bazel workspace).
+#
+# Structure:
+#   external_crate/           <- Outside Cargo workspace
+#   cargo_workspace/          <- Cargo workspace root
+#     Cargo.toml              <- [workspace] members = ["member"]
+#     member/
+#       Cargo.toml            <- external_crate = { path = "../../external_crate" }
+#
+# This should work but currently fails because crate_universe doesn't copy
+# the external path dependency into the temp splicing directory.
+crate = use_extension("@rules_rust//crate_universe:extensions.bzl", "crate")
+crate.from_cargo(
+    name = "crates",
+    cargo_lockfile = "//cargo_workspace:Cargo.lock",
+    manifests = ["//cargo_workspace:Cargo.toml"],
+)
+use_repo(crate, "crates")

test/integration/external_relative_path_deps/MODULE.bazel.lock

@@ -0,0 +1,40 @@
+# External Relative Path Dependencies Test (Issue #3089)
+
+This test validates that crate_universe correctly handles Cargo workspace members
+with path dependencies that point **outside the Cargo workspace root** (but still
+inside the Bazel workspace).
+
+## Structure
+
+```
+external_relative_path_deps/     # Bazel workspace root
+├── MODULE.bazel
+├── BUILD.bazel
+├── external_crate/              # Outside Cargo workspace, inside Bazel workspace
+│   ├── Cargo.toml
+│   └── src/lib.rs
+└── cargo_workspace/             # Cargo workspace root
+    ├── Cargo.toml               # [workspace] with members = ["member"]
+    ├── Cargo.lock
+    └── member/
+        ├── Cargo.toml           # Has path = "../../external_crate"
+        └── src/lib.rs
+```
+
+## The Bug
+
+When `cargo_workspace/member/Cargo.toml` has:
+```toml
+[dependencies]
+external_crate = { path = "../../external_crate" }
+```
+
+crate_universe fails because it doesn't copy `external_crate` into the temp
+directory used for splicing.
+
+## Running the test
+
+```sh
+cd test/integration/external_relative_path_deps
+bazel build //cargo_workspace/member
+```

test/integration/external_relative_path_deps/README.md

@@ -0,0 +1 @@
+# Empty WORKSPACE for Bazel compatibility

test/integration/external_relative_path_deps/WORKSPACE.bazel

@@ -0,0 +1,4 @@
+exports_files([
+    "Cargo.toml",
+    "Cargo.lock",
+])