Internal change

rust/bazel/aspects.bzl

@@ -27,8 +27,10 @@ CrateMappingInfo = provider(
 RustProtoInfo = provider(
     doc = "Rust protobuf provider info",
     fields = {
-        "dep_variant_infos": "List of DepVariantInfo for the compiled Rust " +
-                             "gencode (also covers its transitive dependencies)",
+        "dep_variant_infos": "List of DepVariantInfo for the compiled Rust gencode",
+        "exports_dep_variant_infos": "List(DepVariantInfo): Transitive infos from targets from the proto_library.exports attribute. \
+        This is a list instead of a depset, since we pass them as direct dependencies when compiling rust code. \
+        We assume the proto exports feature is not widely used in a way where this will lead to unacceptable analysis-time overhead.",
         "crate_mapping": "depset(CrateMappingInfo) containing mappings of all transitive " +
                          "dependencies of the current proto_library.",
     },
@@ -43,6 +45,9 @@ def _rust_version_ge(version):
     return _version_parts(RUST_VERSION) >= _version_parts(version)
 
 def label_to_crate_name(ctx, label, toolchain):
+    return compute_crate_name(ctx.workspace_name, label, toolchain)
+
+def encode_label_as_crate_name(label):
     return label.name.replace("-", "_")
 
 def proto_rust_toolchain_label(is_upb):
@@ -219,7 +224,7 @@ def _compile_cc(
         linking_context = linking_context,
     )
 
-def _compile_rust(ctx, attr, src, extra_srcs, deps, runtime):
+def _compile_rust(ctx, attr, src, extra_srcs, deps, aliases, runtime):
     """Compiles a Rust source file.
 
     Eventually this function could be upstreamed into rules_rust and be made present in rust_common.
@@ -230,6 +235,7 @@ def _compile_rust(ctx, attr, src, extra_srcs, deps, runtime):
       src (File): The crate root source file to be compiled.
       extra_srcs ([File]): Additional source files to include in the crate.
       deps (List[DepVariantInfo]): A list of dependencies needed.
+      aliases (dict[Target, str]): A mapping from dependency target to its crate name.
       runtime: The protobuf runtime target.
 
     Returns:
@@ -238,7 +244,7 @@ def _compile_rust(ctx, attr, src, extra_srcs, deps, runtime):
     toolchain = ctx.toolchains["@rules_rust//rust:toolchain_type"]
     output_hash = repr(hash(src.path))
 
-    crate_name = label_to_crate_name(ctx, ctx.label, toolchain)
+    crate_name = compute_crate_name(ctx, ctx.label, toolchain)
 
     lib_name = "{prefix}{name}-{lib_hash}{extension}".format(
         prefix = "lib",
@@ -285,7 +291,7 @@ def _compile_rust(ctx, attr, src, extra_srcs, deps, runtime):
             # generated code to use a consistent name, even though the actual
             # name of the runtime crate varies depending on the protobuf kernel
             # and build system.
-            aliases = {runtime: "protobuf"},
+            aliases = {runtime: "protobuf"} | aliases,
             output = lib,
             metadata = rmeta,
             edition = "2024",
@@ -296,7 +302,7 @@ def _compile_rust(ctx, attr, src, extra_srcs, deps, runtime):
             owner = ctx.label,
         ),
         # Needed to make transitive public imports not violate layering.
-        force_all_deps_direct = True,
+        # force_all_deps_direct = True,
         output_hash = output_hash,
     )
 
@@ -339,12 +345,19 @@ def _rust_proto_aspect_common(target, ctx, is_upb):
     for info in [d[RustProtoInfo].dep_variant_infos for d in proto_deps]:
         dep_variant_infos += info
 
+    exported_proto_deps = getattr(ctx.rule.attr, "exports", [])
+    exports_dep_variant_infos = []
+    for d in exported_proto_deps:
+        exports_dep_variant_infos.extend(d[RustProtoInfo].dep_variant_infos)
+        exports_dep_variant_infos.extend(d[RustProtoInfo].exports_dep_variant_infos)
+
     # If there are no srcs, then this is an alias library (which in Rust acts as a middle
     # library in a dependency chain). Don't generate any Rust code for it, but do propagate the
     # crate mappings.
     if not proto_srcs:
         return [RustProtoInfo(
             dep_variant_infos = dep_variant_infos,
+            exports_dep_variant_infos = exports_dep_variant_infos,
             crate_mapping = depset(transitive = transitive_crate_mappings),
         )]
 
@@ -415,19 +428,37 @@ def _rust_proto_aspect_common(target, ctx, is_upb):
         for dep in ctx.attr._extra_deps
     ]
 
+    proto_deps_for_aliases = dep_variant_infos + exports_dep_variant_infos
+
+    aliases = {}
+
+    for d in proto_deps_for_aliases:
+        label = Label(d.crate_info.owner)
+        target = struct(label = label)
+        qualified_name = encode_label_as_crate_name(label)
+        aliases[target] = qualified_name
+
+    deps = ([dep_variant_info_for_runtime] +
+            dep_variant_info_for_native_gencode +
+            dep_variant_infos +
+            extra_dep_variant_infos +
+            exports_dep_variant_infos)
+
     dep_variant_info = _compile_rust(
         ctx = ctx,
         attr = ctx.rule.attr,
         src = entry_point_rs_output,
         extra_srcs = rs_gencode,
-        deps = [dep_variant_info_for_runtime] + dep_variant_info_for_native_gencode + dep_variant_infos + extra_dep_variant_infos,
+        deps = deps,
+        aliases = aliases,
         runtime = runtime,
     )
     return [RustProtoInfo(
         dep_variant_infos = [dep_variant_info],
+        exports_dep_variant_infos = exports_dep_variant_infos,
         crate_mapping = depset(
             direct = [CrateMappingInfo(
-                crate_name = label_to_crate_name(ctx, target.label, toolchain),
+                crate_name = encode_label_as_crate_name(ctx.label),
                 import_paths = tuple([get_import_path(f) for f in proto_srcs]),
             )],
             transitive = transitive_crate_mappings,
@@ -437,7 +468,7 @@ def _rust_proto_aspect_common(target, ctx, is_upb):
 def _make_proto_library_aspect(is_upb):
     return aspect(
         implementation = (_rust_upb_proto_aspect_impl if is_upb else _rust_cc_proto_aspect_impl),
-        attr_aspects = ["deps"],
+        attr_aspects = ["deps", "exports"],
         requires = ([] if is_upb else [cc_proto_aspect]),
         attrs = {
             "_collect_cc_coverage": attr.label(