Clean up generated code and implement strip_boilerplate

Remove redundant newlines and duplicate headers from generated files
and prevent the creation of empty sub-modules. Implement the
`strip_boilerplate` function to remove generated headers and
attributes, including a comprehensive test suite.

codegen/src/generator.rs

@@ -8,8 +8,7 @@ use std::collections::{HashMap, HashSet};
 use std::str;
 
 const DATA_IMPORTS: &str = "use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint, RepeatedFieldIterator, RotoMessage};\nuse core::str;\n#[cfg(feature = \"alloc\")]\nuse bytes::{Bytes, BytesMut, Buf, BufMut};\n";
-const SERVICE_IMPORTS: &str =
-    "#[cfg(feature = \"alloc\")]\nuse tonic::{Request, Response, Status};\n\
+const SERVICE_IMPORTS: &str = "#[cfg(feature = \"alloc\")]\nuse tonic::{Request, Response, Status};\n\
      #[cfg(feature = \"alloc\")]\nuse tokio_stream::Stream;\n\
      #[cfg(feature = \"alloc\")]\nuse std::pin::Pin;\n\
      #[cfg(feature = \"alloc\")]\nuse std::sync::Arc;\n\
@@ -591,7 +590,7 @@ where
 
         let mut output = String::new();
         output.push_str("// @generated by protoc-gen-roto — do not edit\n");
-        output.push_str("#[allow(unused_imports)]\n\n");
+        output.push_str("#[allow(unused_imports)]\n");
         output.push_str(imports);
 
         for dep_res in file_proto.dependency() {
@@ -636,10 +635,12 @@ where
     }
 
     let mut root_mod_content = String::new();
-    root_mod_content.push_str("// @generated by protoc-gen-roto — do not edit\n");
-    root_mod_content.push_str("#![allow(unused_imports)]\n\n");
     let mut sorted_root_mods: Vec<_> = root_mods.into_iter().collect();
     sorted_root_mods.sort();
+    if sorted_root_mods.is_empty() {
+        root_mod_content.push_str("// @generated by protoc-gen-roto — do not edit\n");
+        root_mod_content.push_str("#![allow(unused_imports)]\n\n");
+    }
     for m in sorted_root_mods {
         root_mod_content.push_str(&format!("pub mod {};\n", m));
     }
@@ -647,6 +648,9 @@ where
 
     for (mod_path, sub_mods) in mod_files {
         let mut content = String::new();
+        if sub_mods.is_empty() {
+            continue;
+        }
         content.push_str("// @generated by protoc-gen-roto — do not edit\n");
         content.push_str("#![allow(unused_imports)]\n\n");
         let mut sorted_subs: Vec<_> = sub_mods.into_iter().collect();
@@ -759,7 +763,65 @@ pub fn generate_rust_code(
 }
 
 fn strip_boilerplate(content: &str) -> String {
-    content.to_string()
+    let mut stripped = content;
+    let header = "// @generated by protoc-gen-roto — do not edit\n";
+    if stripped.starts_with(header) {
+        stripped = &stripped[header.len()..];
+
+        let patterns = [
+            "#[allow(unused_imports)]\n",
+            "#![allow(unused_imports)]\n\n",
+            "#![allow(unused_imports)]\n",
+        ];
+
+        for pattern in patterns {
+            if stripped.starts_with(pattern) {
+                stripped = &stripped[pattern.len()..];
+                break;
+            }
+        }
+    }
+    stripped.to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_strip_boilerplate_standard() {
+        let content = "// @generated by protoc-gen-roto — do not edit\n#[allow(unused_imports)]\nuse std::str;\n";
+        let stripped = strip_boilerplate(content);
+        assert_eq!(stripped, "use std::str;\n");
+    }
+
+    #[test]
+    fn test_strip_boilerplate_crate_level() {
+        let content = "// @generated by protoc-gen-roto — do not edit\n#![allow(unused_imports)]\n\nuse std::str;\n";
+        let stripped = strip_boilerplate(content);
+        assert_eq!(stripped, "use std::str;\n");
+    }
+
+    #[test]
+    fn test_strip_boilerplate_crate_level_single_newline() {
+        let content = "// @generated by protoc-gen-roto — do not edit\n#![allow(unused_imports)]\nuse std::str;\n";
+        let stripped = strip_boilerplate(content);
+        assert_eq!(stripped, "use std::str;\n");
+    }
+
+    #[test]
+    fn test_strip_boilerplate_no_boilerplate() {
+        let content = "use std::str;\n";
+        let stripped = strip_boilerplate(content);
+        assert_eq!(stripped, "use std::str;\n");
+    }
+
+    #[test]
+    fn test_strip_boilerplate_only_header() {
+        let content = "// @generated by protoc-gen-roto — do not edit\n";
+        let stripped = strip_boilerplate(content);
+        assert_eq!(stripped, "");
+    }
 }
 
 fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut String) {

roto-tonic/src/generated/interop.rs

@@ -1,6 +1,5 @@
 // @generated by protoc-gen-roto — do not edit
 #[allow(unused_imports)]
-
 use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint, RepeatedFieldIterator, RotoMessage};
 use core::str;
 #[cfg(feature = "alloc")]
@@ -407,9 +406,6 @@ impl roto_runtime::RotoMessage for OwnedStreamingResponse {
 }
 
 
-// @generated by protoc-gen-roto — do not edit
-#[allow(unused_imports)]
-
 
 #[cfg(feature = "alloc")]
 use tonic::{Request, Response, Status};