Update cargo_build_script to work without runfiles support. (#2887)

Partially addresses #1156

This pull-request implements an additional change to enable this
behavior which aggregates all transitive `BuildInfo.compile_data` into
`Rustc` actions. While this seems to bloat these actions with
unnecessary data, it addresses a catastrophic flaw in how Windows works
at all.

As of Bazel 7.3.1, Windows does not run any actions in a sandbox
(bazelbuild/bazel#18401), this means that
references to the current working directory will be consistent since
they always refer to the execroot. On top of this fact,
`cargo_build_script` will assign
[CARGO_MANIFEST_DIR](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates)
to a [path within the runfiles directory of the build
script](https://github.com/bazelbuild/rules_rust/blame/d9ee6172d1dfc2801ba809441668e60e797f89de/cargo/private/cargo_build_script.bzl#L218).
The combination of these two facts leads crates like
[windows_x86_64_msvc](https://crates.io/crates/windows_x86_64_msvc),
which assign a linker path using `CARGO_MANIFEST_DIR`
([@windows_x86_64_msvc//build.rs](https://github.com/microsoft/windows-rs/blob/0.59.0/crates/targets/x86_64_msvc/build.rs#L1-L8))
to introduce un-tracked dependencies into dependent `Rustc` actions.
This then leads to build failures if the `windows_x86_64_msvc` crate is
ever a remote cache hit for the dependents as runfiles (or
`.cargo_runfiles` in the case of this PR) are not fetched and will not
exist on the host at link time.

This change addresses this issue of untracked dependencies by ensuring
the runfiles of `cargo_build_script.script` targets are aggregated into
`Rustc` actions.

.bazelci/presubmit.yml

@@ -36,6 +36,21 @@ default_windows_targets: &default_windows_targets
   - "//..."
   - "-//test/proto/..."
   - "-//test/unit/pipelined_compilation/..."
+default_windows_no_runfiles_targets: &default_windows_no_runfiles_targets
+  - "--" # Allows negative patterns; hack for https://github.com/bazelbuild/continuous-integration/pull/245
+  - "//..."
+  # TODO: https://github.com/bazelbuild/rules_rust/issues/1156
+  - "-//crate_universe/..."
+  - "-//test/chained_direct_deps:mod3_doc_test"
+  - "-//test/out_dir_in_tests:demo_lib_doc_test"
+  - "-//test/proto/..."
+  - "-//test/rustc_env_files:output_test"
+  - "-//test/test_env_launcher:test"
+  - "-//test/test_env:test_manifest_dir"
+  - "-//test/test_env:test_run"
+  - "-//test/unit/pipelined_compilation/..."
+  - "-//test/unit/rustdoc/..."
+  - "-//tools/runfiles/..."
 crate_universe_vendor_example_targets: &crate_universe_vendor_example_targets
   - "//vendor_external:crates_vendor"
   - "//vendor_local_manifests:crates_vendor"
@@ -78,6 +93,15 @@ tasks:
   windows:
     build_targets: *default_windows_targets
     test_targets: *default_windows_targets
+  windows_no_runfiles:
+    name: No Runfiles
+    platform: windows
+    build_flags:
+      - "--noenable_runfiles"
+    test_flags:
+      - "--noenable_runfiles"
+    build_targets: *default_windows_no_runfiles_targets
+    test_targets: *default_windows_no_runfiles_targets
   ubuntu2004_split_coverage_postprocessing:
     name: Split Coverage Postprocessing
     platform: ubuntu2004
@@ -171,6 +195,19 @@ tasks:
       - "--config=clippy"
     build_targets: *default_windows_targets
     test_targets: *default_windows_targets
+  windows_no_runfiles_with_aspects:
+    name: No Runfiles With Aspects
+    platform: windows
+    build_flags:
+      - "--noenable_runfiles"
+      - "--config=rustfmt"
+      - "--config=clippy"
+    test_flags:
+      - "--noenable_runfiles"
+      - "--config=rustfmt"
+      - "--config=clippy"
+    build_targets: *default_windows_no_runfiles_targets
+    test_targets: *default_windows_no_runfiles_targets
   windows_rolling_with_aspects:
     name: "Windows Rolling Bazel Version With Aspects"
     platform: windows

cargo/private/BUILD.bazel

@@ -1,7 +1,13 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load(":runfiles_enabled.bzl", "runfiles_enabled_build_setting")
 
 bzl_library(
     name = "bzl_lib",
     srcs = glob(["**/*.bzl"]),
     visibility = ["//:__subpackages__"],
 )
+
+runfiles_enabled_build_setting(
+    name = "runfiles_enabled",
+    visibility = ["//visibility:public"],
+)

cargo/private/cargo_build_script.bzl

@@ -23,6 +23,7 @@ load(
     "find_toolchain",
     _name_to_crate_name = "name_to_crate_name",
 )
+load(":runfiles_enabled.bzl", "is_runfiles_enabled", "runfiles_enabled_attr")
 
 # Reexport for cargo_build_script_wrapper.bzl
 name_to_crate_name = _name_to_crate_name
@@ -198,6 +199,38 @@ def _feature_enabled(ctx, feature_name, default = False):
 
     return default
 
+def _rlocationpath(file, workspace_name):
+    if file.short_path.startswith("../"):
+        return file.short_path[len("../"):]
+
+    return "{}/{}".format(workspace_name, file.short_path)
+
+def _create_runfiles_dir(ctx, script):
+    runfiles_dir = ctx.actions.declare_directory("{}.cargo_runfiles".format(ctx.label.name))
+
+    # External repos always fall into the `../` branch of `_rlocationpath`.
+    workspace_name = ctx.workspace_name
+
+    def _runfiles_map(file):
+        return "{}={}".format(file.path, _rlocationpath(file, workspace_name))
+
+    runfiles = script[DefaultInfo].default_runfiles
+
+    args = ctx.actions.args()
+    args.use_param_file("@%s", use_always = True)
+    args.add(runfiles_dir.path)
+    args.add_all(runfiles.files, map_each = _runfiles_map, allow_closure = True)
+
+    ctx.actions.run(
+        mnemonic = "CargoBuildScriptRunfilesDir",
+        executable = ctx.executable._runfiles_maker,
+        arguments = [args],
+        inputs = runfiles.files,
+        outputs = [runfiles_dir],
+    )
+
+    return runfiles_dir
+
 def _cargo_build_script_impl(ctx):
     """The implementation for the `cargo_build_script` rule.
 
@@ -208,16 +241,37 @@ def _cargo_build_script_impl(ctx):
         list: A list containing a BuildInfo provider
     """
     script = ctx.executable.script
+    script_info = ctx.attr.script[CargoBuildScriptRunfilesInfo]
     toolchain = find_toolchain(ctx)
     out_dir = ctx.actions.declare_directory(ctx.label.name + ".out_dir")
     env_out = ctx.actions.declare_file(ctx.label.name + ".env")
     dep_env_out = ctx.actions.declare_file(ctx.label.name + ".depenv")
     flags_out = ctx.actions.declare_file(ctx.label.name + ".flags")
     link_flags = ctx.actions.declare_file(ctx.label.name + ".linkflags")
     link_search_paths = ctx.actions.declare_file(ctx.label.name + ".linksearchpaths")  # rustc-link-search, propagated from transitive dependencies
-    manifest_dir = "%s.runfiles/%s/%s" % (script.path, ctx.label.workspace_name or ctx.workspace_name, ctx.label.package)
     compilation_mode_opt_level = get_compilation_mode_opts(ctx, toolchain).opt_level
 
+    script_tools = []
+    script_data = []
+    for target in script_info.data:
+        script_data.append(target[DefaultInfo].files)
+        script_data.append(target[DefaultInfo].default_runfiles.files)
+    for target in script_info.tools:
+        script_tools.append(target[DefaultInfo].files)
+        script_tools.append(target[DefaultInfo].default_runfiles.files)
+
+    workspace_name = ctx.label.workspace_name
+    if not workspace_name:
+        workspace_name = ctx.workspace_name
+
+    if not is_runfiles_enabled(ctx.attr):
+        runfiles_dir = _create_runfiles_dir(ctx, ctx.attr.script)
+        script_data.append(depset([runfiles_dir]))
+        manifest_dir = "{}/{}/{}".format(runfiles_dir.path, workspace_name, ctx.label.package)
+    else:
+        script_data.append(ctx.attr.script[DefaultInfo].default_runfiles.files)
+        manifest_dir = "{}.runfiles/{}/{}".format(script.path, workspace_name, ctx.label.package)
+
     streams = struct(
         stdout = ctx.actions.declare_file(ctx.label.name + ".stdout.log"),
         stderr = ctx.actions.declare_file(ctx.label.name + ".stderr.log"),
@@ -331,8 +385,6 @@ def _cargo_build_script_impl(ctx):
             variables = getattr(target[platform_common.TemplateVariableInfo], "variables", depset([]))
             env.update(variables)
 
-    script_info = ctx.attr.script[CargoBuildScriptRunfilesInfo]
-
     _merge_env_dict(env, expand_dict_value_locations(
         ctx,
         ctx.attr.build_script_env,
@@ -343,15 +395,6 @@ def _cargo_build_script_impl(ctx):
         script_info.tools,
     ))
 
-    script_tools = []
-    script_data = []
-    for target in script_info.data:
-        script_data.append(target[DefaultInfo].files)
-        script_data.append(target[DefaultInfo].default_runfiles.files)
-    for target in script_info.tools:
-        script_tools.append(target[DefaultInfo].files)
-        script_tools.append(target[DefaultInfo].default_runfiles.files)
-
     tools = depset(
         direct = [
             script,
@@ -379,6 +422,7 @@ def _cargo_build_script_impl(ctx):
     args.add(ctx.attr.rundir)
 
     build_script_inputs = []
+
     for dep in ctx.attr.link_deps:
         if rust_common.dep_info in dep and dep[rust_common.dep_info].dep_env:
             dep_env_file = dep[rust_common.dep_info].dep_env
@@ -520,7 +564,14 @@ cargo_build_script = rule(
         "_experimental_symlink_execroot": attr.label(
             default = Label("//cargo/settings:experimental_symlink_execroot"),
         ),
-    },
+        "_runfiles_maker": attr.label(
+            cfg = "exec",
+            executable = True,
+            default = Label("//cargo/private/runfiles_maker"),
+        ),
+    } | runfiles_enabled_attr(
+        default = Label("//cargo/private:runfiles_enabled"),
+    ),
     fragments = ["cpp"],
     toolchains = [
         str(Label("//rust:toolchain_type")),