THRIFT-6059: add crate_prefix option to Rust codegen for cross-file imports

Client: rs

The Rust code generator hardcodes 'use crate::' for cross-file imports
(e.g., when event.thrift includes trees.thrift). This assumes the
generated files are placed at the crate root (src/). When files are
placed in a submodule (e.g., src/thrift/), the correct prefix is
'super', and users must post-process with sed.

Add a crate_prefix generator option: --gen rs:crate_prefix=super

Default remains 'crate' for backward compatibility. An empty value is
rejected since it would silently emit 'use ::module;' (an external
crate path in Rust 2018+). Unknown options are reported with the
generator prefix ('unknown option rs:') per compiler convention.

Co-Authored-By: Grok 4.3 <noreply@x.ai>

Author: 2 people

compiler/cpp/src/thrift/generate/t_rs_generator.cc

@@ -53,9 +53,24 @@ static const string SYNC_CLIENT_GENERIC_BOUNDS("where IP: TInputProtocol, OP: TO
 
 class t_rs_generator : public t_generator {
 public:
-  t_rs_generator(t_program* program, const std::map<std::string, std::string>&, const std::string&)
+  t_rs_generator(t_program* program,
+                 const std::map<std::string, std::string>& parsed_options,
+                 const std::string&)
     : t_generator(program) {
     gen_dir_ = get_out_dir();
+    crate_prefix_ = "crate";
+
+    std::map<std::string, std::string>::const_iterator iter;
+    for (iter = parsed_options.begin(); iter != parsed_options.end(); ++iter) {
+      if (iter->first.compare("crate_prefix") == 0) {
+        if (iter->second.empty()) {
+          throw std::string("crate_prefix requires a non-empty value, e.g. rs:crate_prefix=super");
+        }
+        crate_prefix_ = iter->second;
+      } else {
+        throw "unknown option rs:" + iter->first;
+      }
+    }
 
     fprintf(stderr, "We are sorry, but for the lack of active maintainers, the RUST compiler target is being deprecated and may be removed in the next version. Feel free to contact the dev mailing list (dev@thrift.apache.org) for further details.\n");
 
@@ -91,6 +106,10 @@ class t_rs_generator : public t_generator {
   // Directory to which generated code is written.
   string gen_dir_;
 
+  // Rust path prefix for cross-file imports (default: "crate").
+  // Use --gen rs:crate_prefix=super when generated files are in a submodule.
+  string crate_prefix_;
+
   // File to which generated code is written.
   ofstream_with_content_based_conditional_update f_gen_;
 
@@ -617,10 +636,10 @@ void t_rs_generator::render_attributes_and_includes() {
       string_replace(module_namespace, ".", "::");
 
       if (module_namespace.empty()) {
-        f_gen_ << "use crate::" << rust_snake_case(module_name) << ";" << '\n';
+        f_gen_ << "use " << crate_prefix_ << "::" << rust_snake_case(module_name) << ";" << '\n';
       } else {
-        f_gen_ << "use crate::" << module_namespace << "::" << rust_snake_case(module_name) << ";"
-               << '\n';
+        f_gen_ << "use " << crate_prefix_ << "::" << module_namespace << "::"
+               << rust_snake_case(module_name) << ";" << '\n';
       }
     }
     f_gen_ << '\n';
@@ -3397,4 +3416,9 @@ std::string t_rs_generator::display_name() const {
   return "Rust";
 }
 
-THRIFT_REGISTER_GENERATOR(rs, "Rust", "\n") // no Rust-generator-specific options
+THRIFT_REGISTER_GENERATOR(
+    rs,
+    "Rust",
+    "    crate_prefix=p:  Rust path prefix for cross-file imports (default: crate).\n"
+    "                     Use 'super' when generated files are in a submodule.\n"
+)