C2: export KOTLIN_BANNER and merged_file_path

src/file.rs

@@ -105,7 +105,11 @@ pub fn merge_files(fragments: Vec<KtFile>) -> Result<Vec<KtFile>, WriteKotlinErr
     Ok(groups.into_values().collect())
 }
 
-/// The flattened on-disk path of one merged file under `kotlin_root`.
+/// The flattened on-disk path of one merged file under `kotlin_root`:
+/// `io.zenoh.jni.bytes` becomes `<kotlin_root>/io/zenoh/jni/bytes.kt`.
+///
+/// [`write_files`] uses this to lay out its output; it is public so a consumer
+/// can predict, report or post-process those paths without writing anything.
 /// `fallback_name` names the file when the package is empty.
 pub fn merged_file_path(kotlin_root: &Path, file: &KtFile, fallback_name: &str) -> PathBuf {
     if file.package.is_empty() {

src/lib.rs

@@ -22,7 +22,7 @@ mod types;
 mod tests;
 
 pub use code::KtCode;
-pub use file::{merge_files, write_files, WriteKotlinError};
+pub use file::{merge_files, merged_file_path, write_files, WriteKotlinError};
 pub use ident::{
     escape_kotlin_ident, is_kotlin_hard_keyword, is_valid_kotlin_ident, is_valid_kotlin_package,
     mangle_kotlin_ident, mangle_kotlin_package, KOTLIN_HARD_KEYWORDS,
@@ -32,5 +32,6 @@ pub use model::{
     KtFile, KtFun, KtFunInterface, KtFunSig, KtParam, KtProperty, KtSuperclass, KtSupertypes,
     KtVis,
 };
+pub use render::KOTLIN_BANNER;
 pub use slot::KtPropertyValue;
 pub use types::{ImportSet, KtType};

src/render.rs

@@ -10,7 +10,12 @@ use super::{
     types::{ImportSet, KtType},
 };
 
-/// First line of every generated file.
+/// The default first line of every generated file — the "do not edit" marker
+/// a reader needs to know the file is machine-written.
+///
+/// [`KtFile::banner`] overrides it per file, and `""` suppresses it entirely;
+/// this constant is what an override falls back to, and what a consumer
+/// prepending its own header should match against.
 pub const KOTLIN_BANNER: &str = "// Auto-generated by kotlin-codegen — do not edit by hand.";
 
 /// When a function's single-line signature (from the indentation through the

src/tests.rs

@@ -543,10 +543,10 @@ fn merge_files_groups_by_package_and_rejects_duplicates() {
 #[test]
 fn merged_file_path_is_flattened() {
     let f = KtFile::new("io.zenoh.jni.bytes");
-    let p = file::merged_file_path(std::path::Path::new("/root"), &f, "X");
+    let p = merged_file_path(std::path::Path::new("/root"), &f, "X");
     assert_eq!(p, std::path::PathBuf::from("/root/io/zenoh/jni/bytes.kt"));
     let empty = KtFile::new("");
-    let p2 = file::merged_file_path(std::path::Path::new("/root"), &empty, "NativeHandle");
+    let p2 = merged_file_path(std::path::Path::new("/root"), &empty, "NativeHandle");
     assert_eq!(p2, std::path::PathBuf::from("/root/NativeHandle.kt"));
 }
 
@@ -927,3 +927,19 @@ fn external_and_a_body_are_mutually_exclusive() {
 fn external_cannot_be_passed_as_a_modifier_string() {
     let _ = KtFun::new("f").modifier("external");
 }
+
+/// Both of these were `pub` in private modules — reachable from inside the
+/// crate but not from a consumer. This test is written against the public
+/// paths, so it fails to compile if either is un-exported again.
+#[test]
+fn banner_and_path_helper_are_reachable_from_the_crate_root() {
+    use crate as kotlin_codegen;
+    assert!(kotlin_codegen::KOTLIN_BANNER.starts_with("//"));
+    let f = KtFile::new("io.p");
+    assert_eq!(
+        kotlin_codegen::merged_file_path(std::path::Path::new("/root"), &f, "X"),
+        std::path::PathBuf::from("/root/io/p.kt")
+    );
+    // The default banner is what an un-overridden file actually renders.
+    assert!(f.render().starts_with(kotlin_codegen::KOTLIN_BANNER));
+}