feat(rust): support Comments::PreserveLegalComments (#2615)

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### Description

<!-- Please insert your description here and provide especially info
about the "what" this PR is solving -->

Cargo.toml

@@ -120,6 +120,7 @@ daachorse           = "1.0.0"
 dashmap             = "6.0.0"
 derivative          = "2.2.0"
 dunce               = "1.0.4"                                                                           # Normalize Windows paths to the most compatible format, avoiding UNC where possible
+either              = "1.13.0"
 futures             = "0.3.30"
 glob                = "0.3.1"
 glob-match          = "0.2.1"

crates/rolldown/tests/rolldown/function/comments/preserve_legal_comments/_config.json

@@ -0,0 +1,6 @@
+{
+  "config": {
+    "comments": "preserveLegalComments"
+  },
+  "expectExecuted": false
+}

crates/rolldown/tests/rolldown/function/comments/preserve_legal_comments/artifacts.snap

@@ -0,0 +1,18 @@
+---
+source: crates/rolldown_testing/src/integration_test.rs
+snapshot_kind: text
+---
+# Assets
+
+## main.js
+
+```js
+
+//#region main.js
+//! Some comments1
+/*! Some comments2 */
+foo;
+bar;
+
+//#endregion
+```

crates/rolldown/tests/rolldown/function/comments/preserve_legal_comments/main.js

@@ -0,0 +1,4 @@
+
+//! Some comments1
+/*! Some comments2 */
+foo;bar;

crates/rolldown/tests/snapshots/integration_rolldown__filename_with_hash.snap

@@ -4018,6 +4018,10 @@ snapshot_kind: text
 
 - main-!~{000}~.js => main-TEEZnbpv.js
 
+# tests/rolldown/function/comments/preserve_legal_comments
+
+- main-!~{000}~.js => main-v1eqisai.js
+
 # tests/rolldown/function/define/node_env
 
 - main-!~{000}~.js => main-281Y6vFN.js

crates/rolldown_common/Cargo.toml

@@ -21,6 +21,7 @@ anyhow              = { workspace = true }
 arcstr              = { workspace = true }
 bitflags            = { workspace = true }
 dashmap             = { workspace = true }
+either              = { workspace = true }
 glob-match          = { workspace = true }
 itertools           = { workspace = true }
 lightningcss        = { workspace = true }

crates/rolldown_common/src/inner_bundler_options/types/comments.rs

@@ -14,4 +14,6 @@ pub enum Comments {
   None,
   /// Keep comments as much as possible
   Preserve,
+  /// Keep legal comments only
+  PreserveLegalComments,
 }

crates/rolldown_common/src/module/normal_module.rs

@@ -9,6 +9,8 @@ use crate::{
 use crate::{EcmaAstIdx, EcmaView, IndexModules, Interop, Module, ModuleType};
 use std::ops::{Deref, DerefMut};
 
+use either::Either;
+use oxc::codegen::LegalComment;
 use rolldown_ecmascript::{EcmaAst, EcmaCompiler, PrintOptions};
 use rolldown_rstr::Rstr;
 use rustc_hash::FxHashSet;
@@ -174,21 +176,18 @@ impl NormalModule {
       ModuleRenderArgs::Ecma { ast } => {
         let enable_sourcemap = options.sourcemap.is_some() && !self.is_virtual();
 
-        let enable_comments = match options.comments {
-          Comments::None => false,
-          Comments::Preserve => true,
+        let comments = match options.comments {
+          Comments::None => Either::Left(false),
+          Comments::Preserve => Either::Left(true),
+          Comments::PreserveLegalComments => Either::Right(LegalComment::Inline),
         };
 
         // Because oxc codegen sourcemap is last of sourcemap chain,
         // If here no extra sourcemap need remapping, we using it as final module sourcemap.
         // So here make sure using correct `source_name` and `source_content.
         let render_output = EcmaCompiler::print_with(
           ast,
-          PrintOptions {
-            sourcemap: enable_sourcemap,
-            filename: self.id.to_string(),
-            comments: enable_comments,
-          },
+          PrintOptions { sourcemap: enable_sourcemap, filename: self.id.to_string(), comments },
         );
         if !self.ecma_view.mutations.is_empty() {
           let mut magic_string = string_wizard::MagicString::new(&render_output.code);

crates/rolldown_ecmascript/Cargo.toml

@@ -19,6 +19,7 @@ workspace = true
 [dependencies]
 anyhow         = { workspace = true }
 arcstr         = { workspace = true }
+either         = { workspace = true }
 oxc            = { workspace = true }
 rolldown_error = { workspace = true }
 self_cell      = { workspace = true }

crates/rolldown_ecmascript/src/ecma_compiler.rs

@@ -1,9 +1,10 @@
 use std::path::PathBuf;
 
 use arcstr::ArcStr;
+use either::Either;
 use oxc::{
   allocator::Allocator,
-  codegen::{CodeGenerator, Codegen, CodegenOptions, CodegenReturn},
+  codegen::{CodeGenerator, Codegen, CodegenOptions, CodegenReturn, LegalComment},
   minifier::{Minifier, MinifierOptions},
   parser::{ParseOptions, Parser},
   sourcemap::SourceMap,
@@ -63,10 +64,15 @@ impl EcmaCompiler {
   }
 
   pub fn print_with(ast: &EcmaAst, options: PrintOptions) -> CodegenReturn {
+    let (is_print_full_comments, legal_comments) = match options.comments {
+      Either::Left(value) => (value, LegalComment::None),
+      Either::Right(value) => (false, value),
+    };
     CodeGenerator::new()
       .with_options(CodegenOptions {
-        comments: options.comments,
+        comments: is_print_full_comments,
         source_map_path: options.sourcemap.then(|| PathBuf::from(options.filename)),
+        legal_comments,
         ..CodegenOptions::default()
       })
       .build(ast.program())
@@ -102,7 +108,7 @@ fn basic_test() {
 }
 
 pub struct PrintOptions {
-  pub comments: bool,
+  pub comments: Either</* is print full comments */ bool, LegalComment>,
   pub filename: String,
   pub sourcemap: bool,
 }

crates/rolldown_testing/_config.schema.json

@@ -414,6 +414,13 @@
           "enum": [
             "preserve"
           ]
+        },
+        {
+          "description": "Keep legal comments only",
+          "type": "string",
+          "enum": [
+            "preserveLegalComments"
+          ]
         }
       ]
     },