Fix collecting cc deps in collect_deps (#2699)

In my repo mvukov/rules_ros2#316 I have a
use-case that I want to pass some cc-deps via dep_variant_info as in
https://github.com/mvukov/rules_ros2/pull/316/files#diff-58917867447a8263989afcfff01c87ad154b41562efc3f6d789807efb26e298fR231-R253.
This PR enables that.

rust/private/rustc.bzl

@@ -240,6 +240,7 @@ def collect_deps(
                 crate_deps.append(struct(
                     crate_info = dep_variant_info.crate_info,
                     dep_info = dep_variant_info.dep_info,
+                    cc_info = dep_variant_info.cc_info,
                 ))
 
     aliases = {k.label: v for k, v in aliases.items()}

test/unit/cc_info/cc_info_test.bzl

@@ -1,7 +1,8 @@
 """Unittests for rust rules."""
 
 load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")
-load("//rust:defs.bzl", "rust_binary", "rust_library", "rust_proc_macro", "rust_shared_library", "rust_static_library")
+load("@rules_cc//cc:defs.bzl", "cc_library")
+load("//rust:defs.bzl", "rust_binary", "rust_common", "rust_library", "rust_proc_macro", "rust_shared_library", "rust_static_library")
 
 def _is_dylib_on_windows(ctx):
     return ctx.target_platform_has_constraint(ctx.attr._windows[platform_common.ConstraintValueInfo])
@@ -90,6 +91,16 @@ def _staticlib_provides_cc_info_test_impl(ctx):
     _assert_cc_info_has_library_to_link(env, tut, "staticlib", 2)
     return analysistest.end(env)
 
+def _crate_group_info_provides_cc_info_test_impl(ctx):
+    env = analysistest.begin(ctx)
+    tut = analysistest.target_under_test(env)
+    asserts.true(
+        env,
+        len(tut[rust_common.dep_info].transitive_noncrates.to_list()) == 1,
+        "crate_group_info should provide 1 non-crate transitive dependency",
+    )
+    return analysistest.end(env)
+
 rlib_provides_cc_info_test = analysistest.make(_rlib_provides_cc_info_test_impl)
 rlib_with_dep_only_has_stdlib_linkflags_once_test = analysistest.make(
     _rlib_with_dep_only_has_stdlib_linkflags_once_test_impl,
@@ -101,6 +112,29 @@ cdylib_provides_cc_info_test = analysistest.make(_cdylib_provides_cc_info_test_i
 })
 proc_macro_does_not_provide_cc_info_test = analysistest.make(_proc_macro_does_not_provide_cc_info_test_impl)
 
+crate_group_info_provides_cc_info_test = analysistest.make(_crate_group_info_provides_cc_info_test_impl)
+
+def _rust_cc_injection_impl(ctx):
+    dep_variant_info = rust_common.dep_variant_info(
+        cc_info = ctx.attr.cc_dep[CcInfo],
+        crate_info = None,
+        dep_info = None,
+    )
+    return [
+        rust_common.crate_group_info(
+            dep_variant_infos = depset([dep_variant_info]),
+        ),
+    ]
+
+rust_cc_injection = rule(
+    attrs = {
+        "cc_dep": attr.label(
+            providers = [CcInfo],
+        ),
+    },
+    implementation = _rust_cc_injection_impl,
+)
+
 def _cc_info_test():
     rust_library(
         name = "rlib",
@@ -140,6 +174,23 @@ def _cc_info_test():
         deps = ["//test/unit/native_deps:native_dep"],
     )
 
+    cc_library(
+        name = "cc_lib",
+        srcs = ["foo.cc"],
+    )
+
+    rust_cc_injection(
+        name = "cc_lib_injected",
+        cc_dep = ":cc_lib",
+    )
+
+    rust_library(
+        name = "rust_lib_with_cc_lib_injected",
+        srcs = ["foo.rs"],
+        deps = [":cc_lib_injected"],
+        edition = "2018",
+    )
+
     rlib_provides_cc_info_test(
         name = "rlib_provides_cc_info_test",
         target_under_test = ":rlib",
@@ -164,6 +215,10 @@ def _cc_info_test():
         name = "proc_macro_does_not_provide_cc_info_test",
         target_under_test = ":proc_macro",
     )
+    crate_group_info_provides_cc_info_test(
+        name = "crate_group_info_provides_cc_info_test",
+        target_under_test = ":rust_lib_with_cc_lib_injected",
+    )
 
 def cc_info_test_suite(name):
     """Entry-point macro called from the BUILD file.
@@ -182,5 +237,6 @@ def cc_info_test_suite(name):
             ":cdylib_provides_cc_info_test",
             ":proc_macro_does_not_provide_cc_info_test",
             ":bin_does_not_provide_cc_info_test",
+            ":crate_group_info_provides_cc_info_test",
         ],
     )

test/unit/cc_info/foo.cc

@@ -0,0 +1 @@
+int foo() { return 42; }