bazel: make downstream-facing targets publicly visible

.bazelignore

@@ -5,5 +5,6 @@ src/sta/debug/
 # we use abc from MODULE.bazel
 third-party/abc/
 tmp
-# standalone workspace for downstream consumer tests
+# standalone workspaces for downstream consumer tests
 test/downstream/
+test/visibility/

BUILD.bazel

@@ -227,7 +227,7 @@ cc_library(
     includes = [
         "include",
     ],
-    visibility = ["//:__subpackages__"],
+    visibility = ["//visibility:public"],
     deps = [
         "//src/sta:opensta_lib",
         "@abseil-cpp//absl/base:core_headers",
@@ -251,7 +251,7 @@ cc_library(
         "include",
         "include/ord",
     ],
-    visibility = ["//:__subpackages__"],
+    visibility = ["//visibility:public"],
     deps = ["@abseil-cpp//absl/synchronization"],
 )
 

test/visibility/.bazelversion

@@ -0,0 +1 @@
+8.6.0

test/visibility/BUILD.bazel

@@ -0,0 +1,15 @@
+# Downstream visibility smoke test.
+#
+# Each alias references an OpenROAD target that downstream consumers
+# need.  If any target has visibility restricted to //:__subpackages__,
+# Bazel analysis will fail with a visibility error — proving the bug.
+#
+# Run:  bazelisk build --nobuild :all
+
+[alias(
+    name = t,
+    actual = "@openroad//:" + t,
+) for t in [
+    "openroad_lib",
+    "ord",
+]]

test/visibility/MODULE.bazel

@@ -0,0 +1,12 @@
+"""Minimal downstream consumer that tests Bazel visibility of OpenROAD targets."""
+
+module(
+    name = "visibility-test",
+    version = "0.0.0",
+)
+
+bazel_dep(name = "openroad")
+local_path_override(
+    module_name = "openroad",
+    path = "../..",
+)

test/visibility/README.md

@@ -0,0 +1,34 @@
+# Bazel visibility test for downstream consumers
+
+## Why each target is public
+
+### `openroad_lib` (cc_library) and `ord` (cc_library — headers)
+
+These are the core C++ library and public headers. A downstream
+Bazel consumer that wants to build a custom binary linking against
+the OpenROAD library (rather than just running the prebuilt
+`openroad` binary) must be able to depend on these targets.
+
+### Why NOT the SWIG filegroups
+
+`error_swig`, `error_swig-py`, and `options_swig` stay at
+`//:__subpackages__`. They are referenced by internal subpackages
+(e.g. `//src/gpl:swig` depends on `//:error_swig`), which already
+satisfies the `__subpackages__` visibility check. No downstream
+consumer references them directly.
+
+## How to test
+
+```bash
+cd test/visibility
+bazelisk build --nobuild :all
+```
+
+If any target is not publicly visible, Bazel fails at analysis time:
+
+```
+ERROR: target '@openroad//:openroad_lib' is not visible from
+target '@@visibility-test//:openroad_lib'.
+```
+
+After the fix, the command succeeds (exit 0).