From f9f2bdfd156f62c67af78ed7c0a46ae67ec148e2 Mon Sep 17 00:00:00 2001
From: Lorenz Brun <lorenz@monogon.tech>
Date: Wed, 25 Sep 2024 02:37:42 +0200
Subject: [PATCH 2/4] Support no_std in Prost toolchain

---
 extensions/prost/private/prost.bzl         |  8 ++++++++
 extensions/prost/private/protoc_wrapper.rs | 18 +++++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/extensions/prost/private/prost.bzl b/extensions/prost/private/prost.bzl
index f06719db..6d9d4969 100644
--- a/extensions/prost/private/prost.bzl
+++ b/extensions/prost/private/prost.bzl
@@ -86,6 +86,9 @@ def _compile_proto(
     additional_args.add("--additional_srcs={}".format(",".join([f.path for f in all_additional_srcs.to_list()])))
     additional_args.add_all(prost_toolchain.prost_opts + prost_opts, format_each = "--prost_opt=%s")
 
+    if prost_toolchain.is_nostd:
+        additional_args.add("--is_nostd")
+
     if prost_toolchain.tonic_plugin:
         tonic_plugin = prost_toolchain.tonic_plugin[DefaultInfo].files_to_run
         additional_args.add(prost_toolchain.tonic_plugin_flag % tonic_plugin.executable.path)
@@ -442,6 +445,7 @@ def _rust_prost_toolchain_impl(ctx):
         tonic_plugin_flag = ctx.attr.tonic_plugin_flag,
         tonic_runtime = ctx.attr.tonic_runtime,
         include_transitive_deps = ctx.attr.include_transitive_deps,
+        is_nostd = ctx.attr.is_nostd,
     )]
 
 rust_prost_toolchain = rule(
@@ -497,6 +501,10 @@ rust_prost_toolchain = rule(
             doc = "The Tonic runtime crates to use.",
             providers = [[rust_common.crate_info], [rust_common.crate_group_info]],
         ),
+        "is_nostd": attr.bool(
+            doc = "If a no_std tag should be put into the generated code.",
+            default = False,
+        ),
     }, **proto_toolchains.if_legacy_toolchain({
         "_legacy_proto_toolchain": attr.label(
             default = Label("//private:legacy_proto_toolchain"),
diff --git a/extensions/prost/private/protoc_wrapper.rs b/extensions/prost/private/protoc_wrapper.rs
index a0403f82..1dded7aa 100644
--- a/extensions/prost/private/protoc_wrapper.rs
+++ b/extensions/prost/private/protoc_wrapper.rs
@@ -156,8 +156,17 @@ fn generate_lib_rs(
     is_tonic: bool,
     direct_dep_crate_names: Vec<String>,
     additional_content: String,
+    is_nostd: bool,
 ) -> String {
-    let mut contents = vec!["// @generated".to_string(), "".to_string()];
+    let mut contents = vec![
+        if is_nostd {
+            "#![no_std]".to_string()
+        } else {
+            "".to_string()
+        },
+        "// @generated".to_string(),
+        "".to_string(),
+    ];
     for crate_name in direct_dep_crate_names {
         contents.push(format!("pub use {crate_name};"));
     }
@@ -457,6 +462,9 @@ struct Args {
     /// Whether to generate tonic code.
     is_tonic: bool,
 
+    // Whether to put a no_std tag into the generated code.
+    is_nostd: bool,
+
     /// Extra arguments to pass to protoc.
     extra_args: Vec<String>,
 }
@@ -479,6 +487,7 @@ impl Args {
         let mut tonic_or_prost_opts = Vec::new();
         let mut direct_dep_crate_names = Vec::new();
         let mut is_tonic = false;
+        let mut is_nostd = false;
 
         let mut extra_args = Vec::new();
 
@@ -501,6 +510,10 @@ impl Args {
                 is_tonic = true;
                 return;
             }
+            if arg == "--is_nostd" {
+                is_nostd = true;
+                return;
+            }
 
             if !arg.contains('=') {
                 extra_args.push(arg);
@@ -644,6 +657,7 @@ impl Args {
             proto_paths,
             direct_dep_crate_names,
             is_tonic,
+            is_nostd,
             label: label.unwrap(),
             extra_args,
         })
@@ -748,6 +762,7 @@ fn main() {
         proto_paths,
         direct_dep_crate_names,
         is_tonic,
+        is_nostd,
         extra_args,
     } = Args::parse().expect("Failed to parse args");
 
@@ -917,6 +932,7 @@ fn main() {
             is_tonic,
             direct_dep_crate_names,
             additional_content,
+            is_nostd,
         ),
     )
     .expect("Failed to write file.");
-- 
2.47.0