Add support for rustc flags to rust_proto_library (#1932)

* Add support for rustc flags to `rust_proto_library`

* Regenerate documentation

docs/flatten.md

@@ -594,7 +594,7 @@ Running `bazel test //hello_lib:hello_lib_doc_test` will run all documentation t
 ## rust_grpc_library
 
 <pre>
-rust_grpc_library(<a href="#rust_grpc_library-name">name</a>, <a href="#rust_grpc_library-deps">deps</a>, <a href="#rust_grpc_library-rust_deps">rust_deps</a>)
+rust_grpc_library(<a href="#rust_grpc_library-name">name</a>, <a href="#rust_grpc_library-deps">deps</a>, <a href="#rust_grpc_library-rust_deps">rust_deps</a>, <a href="#rust_grpc_library-rustc_flags">rustc_flags</a>)
 </pre>
 
 Builds a Rust library crate from a set of `proto_library`s suitable for gRPC.
@@ -630,6 +630,7 @@ rust_binary(
 | <a id="rust_grpc_library-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/concepts/labels#target-names">Name</a> | required |  |
 | <a id="rust_grpc_library-deps"></a>deps |  List of proto_library dependencies that will be built. One crate for each proto_library will be created with the corresponding gRPC stubs.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | required |  |
 | <a id="rust_grpc_library-rust_deps"></a>rust_deps |  The crates the generated library depends on.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
+| <a id="rust_grpc_library-rustc_flags"></a>rustc_flags |  List of compiler flags passed to <code>rustc</code>.<br><br>                These strings are subject to Make variable expansion for predefined                 source/output path variables like <code>$location</code>, <code>$execpath</code>, and                  <code>$rootpath</code>. This expansion is useful if you wish to pass a generated                 file of arguments to rustc: <code>@$(location //package:target)</code>.   | List of strings | optional | <code>[]</code> |
 
 
 <a id="rust_library"></a>
@@ -771,7 +772,7 @@ Builds a Rust proc-macro crate.
 ## rust_proto_library
 
 <pre>
-rust_proto_library(<a href="#rust_proto_library-name">name</a>, <a href="#rust_proto_library-deps">deps</a>, <a href="#rust_proto_library-rust_deps">rust_deps</a>)
+rust_proto_library(<a href="#rust_proto_library-name">name</a>, <a href="#rust_proto_library-deps">deps</a>, <a href="#rust_proto_library-rust_deps">rust_deps</a>, <a href="#rust_proto_library-rustc_flags">rustc_flags</a>)
 </pre>
 
 Builds a Rust library crate from a set of `proto_library`s.
@@ -807,6 +808,7 @@ rust_binary(
 | <a id="rust_proto_library-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/concepts/labels#target-names">Name</a> | required |  |
 | <a id="rust_proto_library-deps"></a>deps |  List of proto_library dependencies that will be built. One crate for each proto_library will be created with the corresponding stubs.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | required |  |
 | <a id="rust_proto_library-rust_deps"></a>rust_deps |  The crates the generated library depends on.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
+| <a id="rust_proto_library-rustc_flags"></a>rustc_flags |  List of compiler flags passed to <code>rustc</code>.<br><br>                These strings are subject to Make variable expansion for predefined                 source/output path variables like <code>$location</code>, <code>$execpath</code>, and                  <code>$rootpath</code>. This expansion is useful if you wish to pass a generated                 file of arguments to rustc: <code>@$(location //package:target)</code>.   | List of strings | optional | <code>[]</code> |
 
 
 <a id="rust_proto_toolchain"></a>

docs/rust_proto.md

@@ -120,7 +120,7 @@ configuration.
 ## rust_grpc_library
 
 <pre>
-rust_grpc_library(<a href="#rust_grpc_library-name">name</a>, <a href="#rust_grpc_library-deps">deps</a>, <a href="#rust_grpc_library-rust_deps">rust_deps</a>)
+rust_grpc_library(<a href="#rust_grpc_library-name">name</a>, <a href="#rust_grpc_library-deps">deps</a>, <a href="#rust_grpc_library-rust_deps">rust_deps</a>, <a href="#rust_grpc_library-rustc_flags">rustc_flags</a>)
 </pre>
 
 Builds a Rust library crate from a set of `proto_library`s suitable for gRPC.
@@ -156,14 +156,15 @@ rust_binary(
 | <a id="rust_grpc_library-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/concepts/labels#target-names">Name</a> | required |  |
 | <a id="rust_grpc_library-deps"></a>deps |  List of proto_library dependencies that will be built. One crate for each proto_library will be created with the corresponding gRPC stubs.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | required |  |
 | <a id="rust_grpc_library-rust_deps"></a>rust_deps |  The crates the generated library depends on.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
+| <a id="rust_grpc_library-rustc_flags"></a>rustc_flags |  List of compiler flags passed to <code>rustc</code>.<br><br>                These strings are subject to Make variable expansion for predefined                 source/output path variables like <code>$location</code>, <code>$execpath</code>, and                  <code>$rootpath</code>. This expansion is useful if you wish to pass a generated                 file of arguments to rustc: <code>@$(location //package:target)</code>.   | List of strings | optional | <code>[]</code> |
 
 
 <a id="rust_proto_library"></a>
 
 ## rust_proto_library
 
 <pre>
-rust_proto_library(<a href="#rust_proto_library-name">name</a>, <a href="#rust_proto_library-deps">deps</a>, <a href="#rust_proto_library-rust_deps">rust_deps</a>)
+rust_proto_library(<a href="#rust_proto_library-name">name</a>, <a href="#rust_proto_library-deps">deps</a>, <a href="#rust_proto_library-rust_deps">rust_deps</a>, <a href="#rust_proto_library-rustc_flags">rustc_flags</a>)
 </pre>
 
 Builds a Rust library crate from a set of `proto_library`s.
@@ -199,6 +200,7 @@ rust_binary(
 | <a id="rust_proto_library-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/concepts/labels#target-names">Name</a> | required |  |
 | <a id="rust_proto_library-deps"></a>deps |  List of proto_library dependencies that will be built. One crate for each proto_library will be created with the corresponding stubs.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | required |  |
 | <a id="rust_proto_library-rust_deps"></a>rust_deps |  The crates the generated library depends on.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
+| <a id="rust_proto_library-rustc_flags"></a>rustc_flags |  List of compiler flags passed to <code>rustc</code>.<br><br>                These strings are subject to Make variable expansion for predefined                 source/output path variables like <code>$location</code>, <code>$execpath</code>, and                  <code>$rootpath</code>. This expansion is useful if you wish to pass a generated                 file of arguments to rustc: <code>@$(location //package:target)</code>.   | List of strings | optional | <code>[]</code> |
 
 
 <a id="rust_proto_toolchain"></a>

proto/proto.bzl

@@ -310,6 +310,16 @@ rust_proto_library = rule(
         "rust_deps": attr.label_list(
             doc = "The crates the generated library depends on.",
         ),
+        "rustc_flags": attr.string_list(
+            doc = """\
+                List of compiler flags passed to `rustc`.
+
+                These strings are subject to Make variable expansion for predefined
+                source/output path variables like `$location`, `$execpath`, and 
+                `$rootpath`. This expansion is useful if you wish to pass a generated
+                file of arguments to rustc: `@$(location //package:target)`.
+            """,
+        ),
         "_cc_toolchain": attr.label(
             default = Label("@bazel_tools//tools/cpp:current_cc_toolchain"),
         ),
@@ -388,6 +398,16 @@ rust_grpc_library = rule(
         "rust_deps": attr.label_list(
             doc = "The crates the generated library depends on.",
         ),
+        "rustc_flags": attr.string_list(
+            doc = """\
+                List of compiler flags passed to `rustc`.
+
+                These strings are subject to Make variable expansion for predefined
+                source/output path variables like `$location`, `$execpath`, and 
+                `$rootpath`. This expansion is useful if you wish to pass a generated
+                file of arguments to rustc: `@$(location //package:target)`.
+            """,
+        ),
         "_cc_toolchain": attr.label(
             default = "@bazel_tools//tools/cpp:current_cc_toolchain",
         ),