feat(codegen): print eof legal comments (#7058)

part of https://github.com/oxc-project/oxc/issues/7050

crates/oxc_codegen/src/comment.rs

@@ -50,8 +50,14 @@ impl<'a> Codegen<'a> {
     }
 
     fn is_legal_comment(&self, comment: &Comment) -> bool {
-        (self.options.comments || self.options.legal_comments.is_inline())
-            && comment.is_legal(self.source_text)
+        if self.options.comments {
+            if self.options.legal_comments.is_inline() || self.options.legal_comments.is_none() {
+                return comment.is_legal(self.source_text);
+            }
+        } else if self.options.legal_comments.is_inline() {
+            return comment.is_legal(self.source_text);
+        }
+        false
     }
 
     /// Weather to keep leading comments.
@@ -142,6 +148,18 @@ impl<'a> Codegen<'a> {
         }
     }
 
+    pub(crate) fn try_print_eof_legal_comments(&mut self, comments: &[Comment]) {
+        if !self.options.legal_comments.is_eof() {
+            return;
+        }
+        for c in comments {
+            if c.is_legal(self.source_text) {
+                self.print_comment(c);
+                self.print_hard_newline();
+            }
+        }
+    }
+
     fn print_comments(&mut self, start: u32, comments: &[Comment], unused_comments: Vec<Comment>) {
         if comments.first().is_some_and(|c| c.preceded_by_newline) {
             // Skip printing newline if this comment is already on a newline.

crates/oxc_codegen/src/lib.rs

@@ -183,8 +183,9 @@ impl<'a> Codegen<'a> {
         self
     }
 
-    /// Print a [`Program`] into a string of source code. A source map will be
-    /// generated if [`CodegenOptions::source_map_path`] is set.
+    /// Print a [`Program`] into a string of source code.
+    ///
+    /// A source map will be generated if [`CodegenOptions::source_map_path`] is set.
     #[must_use]
     pub fn build(mut self, program: &Program<'a>) -> CodegenReturn {
         self.quote = if self.options.single_quote { b'\'' } else { b'"' };
@@ -196,8 +197,8 @@ impl<'a> Codegen<'a> {
         if let Some(path) = &self.options.source_map_path {
             self.sourcemap_builder = Some(SourcemapBuilder::new(path, program.source_text));
         }
-
         program.print(&mut self, Context::default());
+        self.try_print_eof_legal_comments(&program.comments);
         let code = self.code.into_string();
         let map = self.sourcemap_builder.map(SourcemapBuilder::into_sourcemap);
         CodegenReturn { code, map }

crates/oxc_codegen/src/options.rs

@@ -19,10 +19,20 @@ pub enum LegalComment {
 }
 
 impl LegalComment {
+    /// Is None.
+    pub fn is_none(self) -> bool {
+        self == Self::None
+    }
+
     /// Is inline mode.
     pub fn is_inline(self) -> bool {
         self == Self::Inline
     }
+
+    /// Is EOF mode.
+    pub fn is_eof(self) -> bool {
+        self == Self::Eof
+    }
 }
 
 /// Codegen Options.

crates/oxc_codegen/tests/integration/legal_comments.rs

@@ -1,4 +1,6 @@
-use crate::snapshot;
+use oxc_codegen::{CodegenOptions, LegalComment};
+
+use crate::{snapshot, snapshot_options};
 
 fn cases() -> Vec<&'static str> {
     vec![
@@ -13,3 +15,9 @@ fn cases() -> Vec<&'static str> {
 fn legal_inline_comment() {
     snapshot("legal_inline_comments", &cases());
 }
+
+#[test]
+fn legal_eof_comment() {
+    let options = CodegenOptions { legal_comments: LegalComment::Eof, ..Default::default() };
+    snapshot_options("legal_eof_comments", &cases(), &options);
+}

crates/oxc_codegen/tests/integration/snapshots/legal_eof_comments.snap

@@ -0,0 +1,42 @@
+---
+source: crates/oxc_codegen/tests/integration/main.rs
+---
+########## 0
+/* @license */
+/* @license */
+foo;bar;
+----------
+foo;
+bar;
+/* @license */
+/* @license */
+
+########## 1
+/* @license */
+/* @preserve */
+foo;bar;
+----------
+foo;
+bar;
+/* @license */
+/* @preserve */
+
+########## 2
+/* @license */
+//! KEEP
+foo;bar;
+----------
+foo;
+bar;
+/* @license */
+//! KEEP
+
+########## 3
+/* @license */
+/*! KEEP */
+foo;bar;
+----------
+foo;
+bar;
+/* @license */
+/*! KEEP */