Support toolchain-driven unused dependencies checking (Starlark changes)

java/common/java_semantics.bzl

@@ -128,5 +128,6 @@ semantics = struct(
     update_args_for_import_deps = _update_args_for_import_deps,
     expand_javacopts_make_variables = True,
     java_toolchain_supports_one_version = _bazel_version_ge("8.0.0"),  # can be dropped once we no longer support Bazel 7
+    create_compilation_action_supports_extra_args = _bazel_version_ge("9.3.0"),
     TEST_SUITE_PROPERTY_NAME = "bazel.test_suite",
 )

java/common/rules/impl/basic_java_library_impl.bzl

@@ -151,6 +151,7 @@ def basic_java_library(
         add_opens = add_opens,
         bootclasspath = bootclasspath[BootClassPathInfo] if bootclasspath else None,
         javabuilder_jvm_flags = javabuilder_jvm_flags,
+        declared_deps = deps,
     )
     target = {"JavaInfo": java_info}
 

java/common/rules/impl/compile_action.bzl

@@ -60,7 +60,8 @@ def compile_action(
         add_exports = [],
         add_opens = [],
         bootclasspath = None,
-        javabuilder_jvm_flags = None):
+        javabuilder_jvm_flags = None,
+        declared_deps = None):
     """
     Creates actions that compile Java sources, produce source jar, and produce header jar and returns JavaInfo.
 
@@ -163,6 +164,7 @@ def compile_action(
         add_opens = add_opens,
         bootclasspath = bootclasspath,
         javabuilder_jvm_flags = javabuilder_jvm_flags,
+        declared_deps = declared_deps,
     )
 
     compilation_info = struct(

java/common/rules/java_package_configuration.bzl

@@ -28,6 +28,7 @@ JavaPackageConfigurationInfo = provider(
         "matches",
         "package_specs",
         "system",
+        "unused_deps_mode",
     ],
 )
 
@@ -50,6 +51,7 @@ def _rule_impl(ctx):
             matches = _matches,
             package_specs = package_specs,
             system = system,
+            unused_deps_mode = ctx.attr.unused_deps_mode if ctx.attr.unused_deps_mode else None,
         ),
     ]
 
@@ -116,6 +118,13 @@ The list of files needed by this configuration at runtime.
             providers = [BootClassPathInfo],
             doc = """
 Corresponds to javac's --system flag.
+""",
+        ),
+        "unused_deps_mode": attr.string(
+            default = "",
+            values = ["", "off", "warn", "error"],
+            doc = """
+Unused dependencies checking mode.
 """,
         ),
         # buildifier: disable=attr-licenses

java/private/java_common.bzl

@@ -65,7 +65,8 @@ def _compile(
         sourcepath = [],
         resources = [],
         neverlink = False,
-        enable_annotation_processing = True):
+        enable_annotation_processing = True,
+        declared_deps = None):
     return _compile_internal(
         ctx,
         output = output,
@@ -88,6 +89,7 @@ def _compile(
         resources = resources,
         neverlink = neverlink,
         enable_annotation_processing = enable_annotation_processing,
+        declared_deps = declared_deps,
     )
 
 def _compile_header(

java/private/java_common_internal.bzl

@@ -20,6 +20,7 @@ load("//java/common/rules:java_helper.bzl", "helper")
 load("//java/common/rules:java_toolchain.bzl", "JavaToolchainInfo")
 load(
     ":java_info.bzl",
+    "JavaInfo",
     "JavaPluginInfo",
     "disable_plugin_info_annotation_processing",
     "java_info_for_compilation",
@@ -134,6 +135,37 @@ def _validate_strict_deps(strict_deps):
         fail("Got an invalid value for strict_deps:", strict_deps, "must be one of:", _STRICT_DEPS_VALUES)
     return strict_deps
 
+def _get_extra_args(ctx, java_toolchain, declared_deps):
+    if not semantics.create_compilation_action_supports_extra_args or not declared_deps:
+        return {}
+
+    matching_modes = {}
+    for package_config in java_toolchain._package_configuration:
+        if package_config.matches(package_config.package_specs, ctx.label):
+            if package_config.unused_deps_mode:
+                matching_modes[package_config.unused_deps_mode] = True
+
+    if not matching_modes:
+        resolved_unused_deps_mode = "off"
+    elif len(matching_modes) == 1:
+        resolved_unused_deps_mode = matching_modes.keys()[0]
+    else:
+        fail("Conflicting unused_deps_mode configurations for target %s: found %s" % (
+            ctx.label,
+            ", ".join(sorted(matching_modes.keys())),
+        ))
+
+    if resolved_unused_deps_mode == "off":
+        return {}
+
+    unused_deps_args = ctx.actions.args()
+    unused_deps_args.add("--experimental_check_unused_deps", resolved_unused_deps_mode.upper())
+    for dep in declared_deps:
+        label = dep.label if hasattr(dep, "label") else dep
+        unused_deps_args.add("--target_declared_deps", str(label))
+
+    return {"extra_args": [unused_deps_args]}
+
 def compile(
         ctx,
         output,
@@ -165,7 +197,8 @@ def compile(
         include_compilation_info = True,
         classpath_resources = [],
         resource_jars = [],
-        injecting_rule_kind = None):
+        injecting_rule_kind = None,
+        declared_deps = None):
     """Compiles Java source files/jars from the implementation of a Starlark rule
 
     The result is a provider that represents the results of the compilation and can be added to the
@@ -215,6 +248,8 @@ def compile(
         add_exports: ([str]) Allow this library to access the given <module>/<package>. Optional.
         add_opens: ([str]) Allow this library to reflectively access the given <module>/<package>.
              Optional.
+        declared_deps: ([Target|Label|str]) The list of declared dependencies for unused dependency checking.
+             Optional.
 
     Returns:
         (JavaInfo)
@@ -314,6 +349,7 @@ def compile(
     if uses_annotation_processing:
         generated_class_jar = _derive_output_file(ctx, output, name_suffix = "-gen")
         generated_source_jar = _derive_output_file(ctx, output, name_suffix = "-gensrc")
+
     get_internal_java_common().create_compilation_action(
         ctx,
         java_toolchain,
@@ -343,6 +379,7 @@ def compile(
         enable_direct_classpath,
         annotation_processor_additional_inputs,
         annotation_processor_additional_outputs,
+        **_get_extra_args(ctx, java_toolchain, declared_deps)
     )
 
     create_output_source_jar = len(source_files) > 0 or source_jars != [output_source_jar]

test/java/toolchains/java_toolchain_tests.bzl

@@ -7,6 +7,7 @@ load("//java:java_binary.bzl", "java_binary")
 load("//java:java_library.bzl", "java_library")
 load("//java:java_plugin.bzl", "java_plugin")
 load("//java/common:java_common.bzl", "java_common")
+load("//java/common/rules:java_package_configuration.bzl", "JavaPackageConfigurationInfo", "java_package_configuration")
 load("//test/java/testutil:java_info_subject.bzl", "java_info_subject")
 load("//test/java/testutil:java_toolchain_info_subject.bzl", "java_toolchain_info_subject")
 load("//test/java/testutil:javac_action_subject.bzl", "javac_action_subject")
@@ -734,6 +735,39 @@ def _test_default_javac_opts_impl(env, target):
         "6",
     ]).in_order()
 
+def _test_java_package_configuration_unused_deps_mode(name):
+    util.helper_target(
+        java_package_configuration,
+        name = name + "/pkg_config",
+        unused_deps_mode = "error",
+    )
+
+    analysis_test(
+        name = name,
+        impl = _test_java_package_configuration_unused_deps_mode_impl,
+        target = name + "/pkg_config",
+    )
+
+def _test_java_package_configuration_unused_deps_mode_impl(env, target):
+    info = target[JavaPackageConfigurationInfo]
+    env.expect.that_str(info.unused_deps_mode).equals("error")
+
+def _test_java_package_configuration_default_unused_deps_mode(name):
+    util.helper_target(
+        java_package_configuration,
+        name = name + "/pkg_config_default",
+    )
+
+    analysis_test(
+        name = name,
+        impl = _test_java_package_configuration_default_unused_deps_mode_impl,
+        target = name + "/pkg_config_default",
+    )
+
+def _test_java_package_configuration_default_unused_deps_mode_impl(env, target):
+    info = target[JavaPackageConfigurationInfo]
+    env.expect.that_bool(info.unused_deps_mode == None).equals(True)
+
 def java_toolchain_tests(name):
     test_suite(
         name = name,
@@ -762,5 +796,7 @@ def java_toolchain_tests(name):
             _test_java_toolchain_flag_set,
             _test_default_javac_opts_depset,
             _test_default_javac_opts,
+            _test_java_package_configuration_unused_deps_mode,
+            _test_java_package_configuration_default_unused_deps_mode,
         ],
     )