Back out "Revert D52499874: [rust] rules: Better handling of exported…

… deps"

Summary:
Original commit changeset: 0a89ff543b1a

Original Phabricator Diff: D52499874

Reviewed By: dtolnay

Differential Revision: D52749218

fbshipit-source-id: dbef3c9f7b65197134bce3bfe9b6119c99ee042c

prelude/rust/link_info.bzl

@@ -150,8 +150,15 @@ RustLinkInfo = provider(
         "linkable_graphs": list[LinkableGraph],
         # LinkGroupLibInfo intentionally omitted because the Rust -> Rust version
         # never needs to be different from the Rust -> native version
-        # The native dependencies reachable from this Rust library through other
-        # Rust libraries
+        #
+        # Rust currently treats all native dependencies as being exported, in
+        # the sense of C++ `exported_deps`. However, they are not only exported
+        # from the Rust library that directly depends on them, they are also
+        # exported through any further chains of Rust libraries. This list
+        # tracks those dependencies
+        #
+        # FIXME(JakobDegen): We should not default to treating all native deps
+        # as exported.
         "exported_link_deps": list[Dependency],
     },
 )

prelude/rust/rust_library.bzl

@@ -547,7 +547,7 @@ def _rust_link_providers(
     inherited_link_infos = inherited_merged_link_infos(ctx, dep_ctx)
     inherited_shlibs = inherited_shared_libs(ctx, dep_ctx)
     inherited_graphs = inherited_linkable_graphs(ctx, dep_ctx)
-    inherited_link_deps = inherited_exported_link_deps(ctx, dep_ctx)
+    inherited_exported_deps = inherited_exported_link_deps(ctx, dep_ctx)
 
     if dep_ctx.advanced_unstable_linking:
         # We have to produce a version of the providers that are defined in such
@@ -557,11 +557,15 @@ def _rust_link_providers(
         #
         # Note that all of this code is FORCE_RLIB specific. Disabling that
         # setting requires replacing this with the "real" native providers
+        #
+        # As an optimization, we never bother reporting exported deps here.
+        # Whichever dependent uses the providers created here will take care of
+        # that for us.
         merged_link_info = create_merged_link_info(
             ctx,
             cxx_toolchain.pic_behavior,
             link_infos,
-            exported_deps = inherited_link_infos,
+            deps = inherited_link_infos,
             preferred_linkage = Linkage("static"),
         )
         shared_libs = merge_shared_libraries(
@@ -584,7 +588,7 @@ def _rust_link_providers(
                 linkable_node = create_linkable_node(
                     ctx = ctx,
                     preferred_linkage = Linkage("static"),
-                    exported_deps = inherited_graphs,
+                    deps = inherited_graphs,
                     link_infos = link_infos,
                     # FIXME(JakobDegen): It should be ok to set this to `None`,
                     # but that breaks arc focus, and setting it to "" breaks
@@ -602,7 +606,7 @@ def _rust_link_providers(
             ctx.actions,
             deps = inherited_shlibs,
         )
-    return (merged_link_info, shared_libs, inherited_graphs, inherited_link_deps)
+    return (merged_link_info, shared_libs, inherited_graphs, inherited_exported_deps)
 
 def _rust_providers(
         ctx: AnalysisContext,
@@ -723,6 +727,7 @@ def _native_providers(
     inherited_link_infos = [rust_link_info.merged_link_info]
     inherited_shlibs = [rust_link_info.shared_libs]
     inherited_link_graphs = rust_link_info.linkable_graphs
+    inherited_exported_deps = rust_link_info.exported_link_deps
 
     linker_info = compile_ctx.cxx_toolchain_info.linker_info
     linker_type = linker_info.type
@@ -739,7 +744,8 @@ def _native_providers(
         ctx,
         compile_ctx.cxx_toolchain_info.pic_behavior,
         link_infos,
-        exported_deps = inherited_link_infos,
+        deps = inherited_link_infos,
+        exported_deps = filter(None, [d.get(MergedLinkInfo) for d in inherited_exported_deps]),
         preferred_linkage = preferred_linkage,
     ))
 
@@ -796,13 +802,14 @@ def _native_providers(
             linkable_node = create_linkable_node(
                 ctx = ctx,
                 preferred_linkage = preferred_linkage,
-                exported_deps = inherited_link_graphs,
+                deps = inherited_link_graphs,
+                exported_deps = inherited_exported_deps,
                 link_infos = link_infos,
                 shared_libs = solibs,
                 default_soname = shlib_name,
             ),
         ),
-        deps = inherited_link_graphs,
+        deps = inherited_link_graphs + inherited_exported_deps,
     )
 
     providers.append(linkable_graph)