Allow empty lists to be omitted in more places in toolchain args

Reviewed By: zertosh

Differential Revision: D41714656

fbshipit-source-id: 00e10288fc0140491ee279aa070b684bc4eee487

prelude/cxx/compile.bzl

@@ -395,8 +395,8 @@ def _supports_dep_files(ext: CxxExtension.type) -> bool.type:
     return True
 
 def _add_compiler_info_flags(compiler_info: "_compiler_info", ext: CxxExtension.type, cmd: "cmd_args"):
-    cmd.add(compiler_info.preprocessor_flags)
-    cmd.add(compiler_info.compiler_flags)
+    cmd.add(compiler_info.preprocessor_flags or [])
+    cmd.add(compiler_info.compiler_flags or [])
     cmd.add(get_flags_for_reproducible_build(compiler_info.compiler_type))
 
     if ext.value not in (".asm", ".asmpp"):

prelude/cxx/cxx_library.bzl

@@ -525,14 +525,14 @@ def cxx_library_parameterized(ctx: "context", impl_params: "CxxRuleConstructorPa
         # and unless they get quoted, they break shell syntax.
         cxx_preprocessor_flags = cmd_args()
         cxx_compiler_info = get_cxx_toolchain_info(ctx).cxx_compiler_info
-        cxx_preprocessor_flags.add(cmd_args(cxx_compiler_info.preprocessor_flags, quote = "shell"))
+        cxx_preprocessor_flags.add(cmd_args(cxx_compiler_info.preprocessor_flags or [], quote = "shell"))
         cxx_preprocessor_flags.add(cmd_args(propagated_preprocessor.set.project_as_args("args"), quote = "shell"))
         cxx_preprocessor_flags.add(propagated_preprocessor.set.project_as_args("include_dirs"))
         templ_vars["cxxppflags"] = cxx_preprocessor_flags
 
         c_preprocessor_flags = cmd_args()
         c_compiler_info = get_cxx_toolchain_info(ctx).c_compiler_info
-        c_preprocessor_flags.add(cmd_args(c_compiler_info.preprocessor_flags, quote = "shell"))
+        c_preprocessor_flags.add(cmd_args(c_compiler_info.preprocessor_flags or [], quote = "shell"))
         c_preprocessor_flags.add(cmd_args(propagated_preprocessor.set.project_as_args("args"), quote = "shell"))
         c_preprocessor_flags.add(propagated_preprocessor.set.project_as_args("include_dirs"))
         templ_vars["cppflags"] = c_preprocessor_flags
@@ -542,7 +542,7 @@ def cxx_library_parameterized(ctx: "context", impl_params: "CxxRuleConstructorPa
             name = "ldflags-" + link_style.value.replace("_", "-")
             args = cmd_args()
             linker_info = get_cxx_toolchain_info(ctx).linker_info
-            args.add(linker_info.linker_flags)
+            args.add(linker_info.linker_flags or [])
             args.add(unpack_link_args(
                 get_link_args(
                     merged_native_link_info,  # buildifier: disable=uninitialized Initialized if impl_params.generate_providers.template_placeholders is True
@@ -896,9 +896,9 @@ def _static_library(
     post_flags = []
 
     if pic:
-        post_flags.extend(linker_info.static_pic_dep_runtime_ld_flags)
+        post_flags.extend(linker_info.static_pic_dep_runtime_ld_flags or [])
     else:
-        post_flags.extend(linker_info.static_dep_runtime_ld_flags)
+        post_flags.extend(linker_info.static_dep_runtime_ld_flags or [])
 
     all_external_debug_info = []
     all_external_debug_info.extend(external_debug_info)
@@ -970,7 +970,7 @@ def _shared_library(
             impl_params.extra_exported_link_flags +
             impl_params.extra_link_flags +
             _attr_post_linker_flags(ctx) +
-            linker_info.shared_dep_runtime_ld_flags
+            (linker_info.shared_dep_runtime_ld_flags or [])
         ),
         external_debug_info = external_debug_info,
     )
@@ -998,9 +998,9 @@ def _shared_library(
             pre_flags = link_info.pre_flags,
             linkables = link_info.linkables,
             post_flags = (
-                link_info.post_flags +
+                (link_info.post_flags or []) +
                 get_ignore_undefined_symbols_flags(linker_info.type) +
-                linker_info.independent_shlib_interface_linker_flags
+                (linker_info.independent_shlib_interface_linker_flags or [])
             ),
             external_debug_info = link_info.external_debug_info,
         )

prelude/cxx/cxx_link_utility.bzl

@@ -197,5 +197,5 @@ def executable_shared_lib_arguments(
 def cxx_link_cmd(ctx: "context") -> "cmd_args":
     toolchain = get_cxx_toolchain_info(ctx)
     command = cmd_args(toolchain.linker_info.linker)
-    command.add(toolchain.linker_info.linker_flags)
+    command.add(toolchain.linker_info.linker_flags or [])
     return command

prelude/rust/build.bzl

@@ -125,7 +125,7 @@ def generate_rustdoc(
         [cmd_args("--env=", k, "=", v, delimiter = "") for k, v in plain_env.items()],
         [cmd_args("--path-env=", k, "=", v, delimiter = "") for k, v in path_env.items()],
         toolchain_info.rustdoc,
-        toolchain_info.rustdoc_flags,
+        toolchain_info.rustdoc_flags or [],
         ctx.attrs.rustdoc_flags,
         common_args.args,
         # FIXME: fbcode/common/rust/rustdoc/compress/main.rs expects
@@ -403,7 +403,8 @@ def _dependency_args(
 
     return (args, crate_targets)
 
-def _lintify(flag: str.type, clippy: bool.type, lints: ["resolved_macro"]) -> "cmd_args":
+def _lintify(flag: str.type, clippy: bool.type, lints: [["resolved_macro"], None]) -> "cmd_args":
+    lints = lints or []
     return cmd_args(
         [lint for lint in lints if str(lint).startswith("\"clippy::") == clippy],
         format = "-{}{{}}".format(flag),
@@ -486,8 +487,8 @@ def _compute_common_args(
         "--json=diagnostic-rendered-ansi",
         ["-Cprefer-dynamic=yes"] if crate_type == CrateType("dylib") else [],
         ["--target={}".format(toolchain_info.rustc_target_triple)] if toolchain_info.rustc_target_triple else [],
-        toolchain_info.rustc_flags,
-        toolchain_info.rustc_check_flags if is_check else [],
+        toolchain_info.rustc_flags or [],
+        (toolchain_info.rustc_check_flags or []) if is_check else [],
         ctx.attrs.rustc_flags,
         cmd_args(ctx.attrs.features, format = '--cfg=feature="{}"'),
         dependency_args,

prelude/rust/rust_binary.bzl

@@ -107,7 +107,7 @@ def _rust_binary_common(
             shared_libs,
         )
 
-        extra_flags = toolchain_info.rustc_binary_flags + (extra_flags or [])
+        extra_flags = (toolchain_info.rustc_binary_flags or []) + (extra_flags or [])
 
         # Compile rust binary.
         link, meta = rust_compile_multi(

shim/toolchain.bzl

@@ -48,16 +48,11 @@ def _cxx_toolchain(ctx):
             mk_comp_db = ctx.attrs.make_comp_db,
             linker_info = LinkerInfo(
                 linker = RunInfo(args = ["gcc"]),
-                linker_flags = [],
                 archiver = RunInfo(args = ["ar", "rcs"]),
                 type = "gnu",
                 link_binaries_locally = True,
                 archive_objects_locally = True,
                 use_archiver_flags = False,
-                static_dep_runtime_ld_flags = [],
-                static_pic_dep_runtime_ld_flags = [],
-                shared_dep_runtime_ld_flags = [],
-                independent_shlib_interface_linker_flags = [],
                 mk_shlib_intf = ctx.attrs.make_shlib_intf,
                 link_style = LinkStyle(ctx.attrs.link_style),
                 link_weight = 1,
@@ -79,26 +74,18 @@ def _cxx_toolchain(ctx):
             ),
             cxx_compiler_info = CxxCompilerInfo(
                 compiler = RunInfo(args = ["clang++"]),
-                preprocessor_flags = [],
-                compiler_flags = [],
                 compiler_type = "clang",  # one of CxxToolProviderType
             ),
             c_compiler_info = CCompilerInfo(
                 compiler = RunInfo(args = ["clang"]),
-                preprocessor_flags = [],
-                compiler_flags = [],
                 compiler_type = "clang",  # one of CxxToolProviderType
             ),
             as_compiler_info = CCompilerInfo(
                 compiler = RunInfo(args = ["clang"]),
-                preprocessor_flags = [],
-                compiler_flags = [],
                 compiler_type = "clang",  # one of CxxToolProviderType
             ),
             asm_compiler_info = CCompilerInfo(
                 compiler = RunInfo(args = ["clang"]),
-                preprocessor_flags = [],
-                compiler_flags = [],
                 compiler_type = "clang",  # one of CxxToolProviderType
             ),
             header_mode = HeaderMode("symlink_tree_only"),
@@ -168,25 +155,18 @@ def _rust_toolchain(ctx):
     return [
         DefaultInfo(),
         RustToolchainInfo(
-            allow_lints = [],
             clippy_driver = "clippy-driver",
             compiler = "rustc",
-            deny_lints = [],
             extern_html_root_url_prefix = "",
             failure_filter = False,
             failure_filter_action = None,
             pipelined = False,
             report_unused_deps = False,
             rustc_action = ctx.attrs.rustc_action[RunInfo],
-            rustc_binary_flags = [],
-            rustc_check_flags = [],
-            rustc_flags = [],
             default_edition = "2021",
             rustc_target_triple = "x86_64-pc-windows-gnu" if host_info().os.is_windows else "x86_64-unknown-linux-gnu",
             rustc_test_flags = "",
             rustdoc = "rustdoc",
-            rustdoc_flags = [],
-            warn_lints = [],
         ),
         RustPlatformInfo(
             name = "x86_64",