feat: make source path prefix configurable

BUILD.bazel

@@ -1,5 +1,5 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
-load("//rust:defs.bzl", "capture_clippy_output", "clippy_flags", "error_format", "extra_exec_rustc_flag", "extra_exec_rustc_flags", "extra_rustc_flag", "extra_rustc_flags", "is_proc_macro_dep", "is_proc_macro_dep_enabled")
+load("//rust:defs.bzl", "capture_clippy_output", "clippy_flags", "error_format", "extra_exec_rustc_flag", "extra_exec_rustc_flags", "extra_rustc_flag", "extra_rustc_flags", "is_proc_macro_dep", "is_proc_macro_dep_enabled", "source_path_prefix")
 
 exports_files(["LICENSE"])
 
@@ -76,6 +76,15 @@ extra_exec_rustc_flag(
     visibility = ["//visibility:public"],
 )
 
+# This setting may be used to override the prefix for source paths rustc embeds into build artifacts.
+# Setting this setting to a fixed value (e.g., "/source/") can help achieve reproducible builds and
+# improve cache utilization.
+source_path_prefix(
+    name = "source_path_prefix",
+    build_setting_default = ".",
+    visibility = ["//visibility:public"],
+)
+
 # This setting is used by the clippy rules. See https://bazelbuild.github.io/rules_rust/rust_clippy.html
 label_flag(
     name = "clippy.toml",

docs/BUILD.bazel

@@ -56,6 +56,7 @@ PAGES = dict([
             "error_format",
             "extra_rustc_flag",
             "extra_rustc_flags",
+            "source_path_prefix",
             "capture_clippy_output",
         ],
     ),

docs/defs.md

@@ -11,6 +11,7 @@
 * [error_format](#error_format)
 * [extra_rustc_flag](#extra_rustc_flag)
 * [extra_rustc_flags](#extra_rustc_flags)
+* [source_path_prefix](#source_path_prefix)
 * [capture_clippy_output](#capture_clippy_output)
 
 <a id="capture_clippy_output"></a>
@@ -586,6 +587,24 @@ Run the test with `bazel test //hello_lib:greeting_test`.
 | <a id="rust_test-version"></a>version |  A version to inject in the cargo environment variable.   | String | optional | "0.0.0" |
 
 
+<a id="source_path_prefix"></a>
+
+## source_path_prefix
+
+<pre>
+source_path_prefix(<a href="#source_path_prefix-name">name</a>)
+</pre>
+
+Specify the path for the compiler to remap the source path prefix in all output, including compiler diagnostics,debug information, and macro expansions with `--@rules_rust//:source_path_prefix`.Setting the prefix a fixed value enables reproducible builds that do not depend on the location of the source directory.
+
+**ATTRIBUTES**
+
+
+| Name  | Description | Type | Mandatory | Default |
+| :------------- | :------------- | :------------- | :------------- | :------------- |
+| <a id="source_path_prefix-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/docs/build-ref.html#name">Name</a> | required |  |
+
+
 <a id="rust_test_suite"></a>
 
 ## rust_test_suite

docs/flatten.md

@@ -50,6 +50,7 @@
 * [rust_wasm_bindgen_toolchain](#rust_wasm_bindgen_toolchain)
 * [rustfmt_aspect](#rustfmt_aspect)
 * [rustfmt_test](#rustfmt_test)
+* [source_path_prefix](#source_path_prefix)
 
 
 <a id="capture_clippy_output"></a>
@@ -1352,6 +1353,24 @@ A test rule for performing `rustfmt --check` on a set of targets
 | <a id="rustfmt_test-targets"></a>targets |  Rust targets to run <code>rustfmt --check</code> on.   | <a href="https://bazel.build/docs/build-ref.html#labels">List of labels</a> | optional | [] |
 
 
+<a id="source_path_prefix"></a>
+
+## source_path_prefix
+
+<pre>
+source_path_prefix(<a href="#source_path_prefix-name">name</a>)
+</pre>
+
+Specify the path for the compiler to remap the source path prefix in all output, including compiler diagnostics,debug information, and macro expansions with `--@rules_rust//:source_path_prefix`.Setting the prefix a fixed value enables reproducible builds that do not depend on the location of the source directory.
+
+**ATTRIBUTES**
+
+
+| Name  | Description | Type | Mandatory | Default |
+| :------------- | :------------- | :------------- | :------------- | :------------- |
+| <a id="source_path_prefix-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/docs/build-ref.html#name">Name</a> | required |  |
+
+
 <a id="CrateInfo"></a>
 
 ## CrateInfo

docs/symbols.bzl

@@ -64,6 +64,7 @@ load(
     _rust_test_suite = "rust_test_suite",
     _rustfmt_aspect = "rustfmt_aspect",
     _rustfmt_test = "rustfmt_test",
+    _source_path_prefix = "source_path_prefix",
 )
 load(
     "@rules_rust//rust:repositories.bzl",
@@ -163,6 +164,7 @@ rustfmt_test = _rustfmt_test
 error_format = _error_format
 extra_rustc_flag = _extra_rustc_flag
 extra_rustc_flags = _extra_rustc_flags
+source_path_prefix = _source_path_prefix
 incompatible_flag = _incompatible_flag
 capture_clippy_output = _capture_clippy_output
 

rust/defs.bzl

@@ -49,6 +49,7 @@ load(
     _extra_rustc_flags = "extra_rustc_flags",
     _is_proc_macro_dep = "is_proc_macro_dep",
     _is_proc_macro_dep_enabled = "is_proc_macro_dep_enabled",
+    _source_path_prefix = "source_path_prefix",
 )
 load(
     "//rust/private:rustdoc.bzl",
@@ -124,6 +125,9 @@ is_proc_macro_dep = _is_proc_macro_dep
 is_proc_macro_dep_enabled = _is_proc_macro_dep_enabled
 # See @rules_rust//rust/private:rustc.bzl for a complete description.
 
+source_path_prefix = _source_path_prefix
+# See @rules_rust//rust/private:rustc.bzl for a complete description.
+
 rust_common = _rust_common
 # See @rules_rust//rust/private:common.bzl for a complete description.
 

rust/private/rust.bzl

@@ -718,6 +718,9 @@ _common_attrs = {
         allow_single_file = True,
         cfg = "exec",
     ),
+    "_source_path_prefix": attr.label(
+        default = Label("//:source_path_prefix"),
+    ),
     "_stamp_flag": attr.label(
         doc = "A setting used to determine whether or not the `--stamp` flag is enabled",
         default = Label("//rust/private:stamp"),

rust/private/rustc.bzl

@@ -90,6 +90,11 @@ is_proc_macro_dep_enabled = rule(
     build_setting = config.bool(flag = True),
 )
 
+SourcePathPrefixInfo = provider(
+    doc = "Remap source path prefixes in all output, including compiler diagnostics, debug information, macro expansions to a path",
+    fields = {"source_path_prefix": "string The path to substitute ${pwd} for"},
+)
+
 def _get_rustc_env(attr, toolchain, crate_name):
     """Gathers rustc environment variables
 
@@ -708,7 +713,7 @@ def construct_arguments(
         force_all_deps_direct = False,
         force_link = False,
         stamp = False,
-        remap_path_prefix = ".",
+        remap_path_prefix = True,
         use_json_output = False,
         build_metadata = False,
         force_depend_on_objects = False):
@@ -737,7 +742,7 @@ def construct_arguments(
         force_link (bool, optional): Whether to add link flags to the command regardless of `emit`.
         stamp (bool, optional): Whether or not workspace status stamping is enabled. For more details see
             https://docs.bazel.build/versions/main/user-manual.html#flag--stamp
-        remap_path_prefix (str, optional): A value used to remap `${pwd}` to. If set to a falsey value, no prefix will be set.
+        remap_path_prefix (bool): Whether to apply the remap-path-prefix compiler setting.
         use_json_output (bool): Have rustc emit json and process_wrapper parse json messages to output rendered output.
         build_metadata (bool): Generate CLI arguments for building *only* .rmeta files. This requires use_json_output.
         force_depend_on_objects (bool): Force using `.rlib` object files instead of metadata (`.rmeta`) files even if they are available.
@@ -874,8 +879,8 @@ def construct_arguments(
     rustc_flags.add("--codegen=debuginfo=" + compilation_mode.debug_info)
 
     # For determinism to help with build distribution and such
-    if remap_path_prefix:
-        rustc_flags.add("--remap-path-prefix=${{pwd}}={}".format(remap_path_prefix))
+    if remap_path_prefix and hasattr(ctx.attr, "_source_path_prefix"):
+        rustc_flags.add("--remap-path-prefix=${{pwd}}={}".format(ctx.attr._source_path_prefix[SourcePathPrefixInfo].source_path_prefix))
 
     if emit:
         rustc_flags.add("--emit=" + ",".join(emit_with_paths))
@@ -1838,6 +1843,19 @@ extra_rustc_flag = rule(
     build_setting = config.string(flag = True, allow_multiple = True),
 )
 
+def _source_path_prefix_impl(ctx):
+    return SourcePathPrefixInfo(source_path_prefix = ctx.build_setting_value)
+
+source_path_prefix = rule(
+    doc = (
+        "Specify the path for the compiler to remap the source path prefix in all output, including compiler diagnostics," +
+        "debug information, and macro expansions with `--@rules_rust//:source_path_prefix`." +
+        "Setting the prefix a fixed value enables reproducible builds that do not depend on the location of the source directory."
+    ),
+    implementation = _source_path_prefix_impl,
+    build_setting = config.string(flag = True),
+)
+
 def _extra_exec_rustc_flags_impl(ctx):
     return ExtraExecRustcFlagsInfo(extra_exec_rustc_flags = ctx.build_setting_value)
 

rust/private/rustdoc.bzl

@@ -120,7 +120,7 @@ def rustdoc_compile_action(
         build_env_files = build_env_files,
         build_flags_files = build_flags_files,
         emit = [],
-        remap_path_prefix = None,
+        remap_path_prefix = False,
         force_link = True,
         force_depend_on_objects = is_test,
     )