add file header customize option

Signed-off-by: Matt Klein <[email protected]>

Author: mattklein123

protobuf-codegen/src/customize/mod.rs

@@ -113,6 +113,8 @@ pub struct Customize {
     pub(crate) inside_protobuf: Option<bool>,
     /// When true, protobuf maps are represented with `std::collections::BTreeMap`
     pub(crate) btreemap: Option<bool>,
+    /// Optional file header to insert at the top of every file.
+    pub(crate) file_header: Option<String>,
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -157,6 +159,11 @@ impl Customize {
         self
     }
 
+    pub fn file_header(mut self, file_header: String) -> Self {
+        self.file_header = Some(file_header);
+        self
+    }
+
     /// Generate code for "lite runtime". Generated code contains no code for reflection.
     /// So the generated code (and more importantly, generated binary size) is smaller,
     /// but reflection, text format, JSON serialization won't work.
@@ -220,6 +227,9 @@ impl Customize {
         if let Some(v) = that.oneofs_non_exhaustive {
             self.oneofs_non_exhaustive = Some(v);
         }
+        if let Some(v) = &that.file_header {
+            self.file_header = Some(v.clone());
+        }
     }
 
     /// Update unset fields of self with fields from other customize

protobuf-codegen/src/customize/rustproto_proto.rs

@@ -28,6 +28,7 @@ pub(crate) fn customize_from_rustproto_for_message(source: &MessageOptions) -> C
         gen_mod_rs,
         inside_protobuf,
         btreemap,
+        file_header: None,
     }
 }
 
@@ -57,6 +58,7 @@ pub(crate) fn customize_from_rustproto_for_field(source: &FieldOptions) -> Custo
         gen_mod_rs,
         inside_protobuf,
         btreemap,
+        file_header: None,
     }
 }
 
@@ -82,5 +84,6 @@ pub(crate) fn customize_from_rustproto_for_file(source: &FileOptions) -> Customi
         inside_protobuf,
         gen_mod_rs,
         btreemap,
+        file_header: None,
     }
 }

protobuf-codegen/src/gen/file.rs

@@ -54,6 +54,10 @@ pub(crate) fn gen_file(
     let lite_runtime = customize.for_elem.lite_runtime.unwrap_or(false);
 
     let v = CodeWriter::with(|w| {
+        if let Some(file_header) = customize.for_elem.file_header.as_ref() {
+            w.write_line(file_header);
+        }
+
         w.write_generated_by("rust-protobuf", env!("CARGO_PKG_VERSION"), parser);
 
         w.write_line("");