fix(codegen): print legal comments above directives

Fixes #14953

Legal comments (e.g., `/*! ... */`) that appear before directives like
"use strict" are now properly preserved in the generated code.

The fix adds `print_comments_at(self.span.start)` to the Directive::gen
implementation to ensure leading comments are printed before directives,
matching the behavior of statements.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Boshen

crates/oxc_codegen/src/gen.rs

@@ -68,6 +68,7 @@ impl Gen for Hashbang<'_> {
 
 impl Gen for Directive<'_> {
     fn r#gen(&self, p: &mut Codegen, _ctx: Context) {
+        p.print_comments_at(self.span.start);
         p.add_source_mapping(self.span);
         p.print_indent();
         // A Use Strict Directive may not contain an EscapeSequence or LineContinuation.

crates/oxc_codegen/tests/integration/comments.rs

@@ -224,6 +224,8 @@ pub mod legal {
 * @preserve
 */
 ",
+            // Issue #14953: legal comments above directives
+            "/*!\n * legal comment\n */\n\n\"use strict\";\n\nexport const foo = 'foo';",
         ]
     }
 

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

@@ -1,5 +1,5 @@
 ---
-source: crates/oxc_codegen/tests/integration/main.rs
+source: crates/oxc_codegen/tests/integration/tester.rs
 ---
 ########## 0
 /* @license */
@@ -127,3 +127,19 @@ function foo() {
 /**
 * @preserve
 */
+
+########## 9
+/*!
+ * legal comment
+ */
+
+"use strict";
+
+export const foo = 'foo';
+----------
+'use strict';
+export const foo = 'foo';
+
+/*!
+* legal comment
+*/

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

@@ -1,5 +1,5 @@
 ---
-source: crates/oxc_codegen/tests/integration/main.rs
+source: crates/oxc_codegen/tests/integration/tester.rs
 ---
 ########## 0
 /* @license */
@@ -109,3 +109,17 @@ function foo(){(()=>{
 /**
 * @preserve
 */
+
+########## 9
+/*!
+ * legal comment
+ */
+
+"use strict";
+
+export const foo = 'foo';
+----------
+'use strict';export const foo=`foo`;
+/*!
+* legal comment
+*/

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

@@ -1,5 +1,5 @@
 ---
-source: crates/oxc_codegen/tests/integration/main.rs
+source: crates/oxc_codegen/tests/integration/tester.rs
 ---
 ########## 0
 /* @license */
@@ -112,3 +112,18 @@ function foo() {
 /**
 * @preserve
 */
+
+########## 9
+/*!
+ * legal comment
+ */
+
+"use strict";
+
+export const foo = 'foo';
+----------
+/*!
+* legal comment
+*/
+'use strict';
+export const foo = 'foo';

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

@@ -1,5 +1,5 @@
 ---
-source: crates/oxc_codegen/tests/integration/main.rs
+source: crates/oxc_codegen/tests/integration/tester.rs
 ---
 ########## 0
 /* @license */
@@ -108,3 +108,16 @@ function foo() {
 */
 
 /*! For license information please see test.js */
+########## 9
+/*!
+ * legal comment
+ */
+
+"use strict";
+
+export const foo = 'foo';
+----------
+'use strict';
+export const foo = 'foo';
+
+/*! For license information please see test.js */

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

@@ -21,6 +21,7 @@ fn();
     throw new Error()
           ^
 
+
 Error
     at fn (/project/input.js:3:11)
     at <anonymous> (/project/input.js:5:1)
@@ -48,6 +49,7 @@ obj.fn();
         throw new Error()
               ^
 
+
 Error
     at Object.fn (/project/input.js:4:15)
     at <anonymous> (/project/input.js:7:5)
@@ -77,6 +79,7 @@ obj.obj2.fn();
             throw new Error()
                   ^
 
+
 Error
     at Object.fn (/project/input.js:5:19)
     at <anonymous> (/project/input.js:9:10)
@@ -108,6 +111,7 @@ obj.fn()();
             throw new Error()
                   ^
 
+
 Error
     at fn2 (/project/input.js:5:19)
     at <anonymous> (/project/input.js:9:9)
@@ -139,6 +143,7 @@ obj.fn([1])();
             throw new Error()
                   ^
 
+
 Error
     at <anonymous> (/project/input.js:5:19)
     at <anonymous> (/project/input.js:9:12)
@@ -172,6 +177,7 @@ obj.fn({ a })();
             throw new Error()
                   ^
 
+
 Error
     at <anonymous> (/project/input.js:6:19)
     at <anonymous> (/project/input.js:10:12)
@@ -201,6 +207,7 @@ fn("name", () => {
     throw new Error()
           ^
 
+
 Error
     at <anonymous> (/project/input.js:6:11)
     at fn (/project/input.js:2:5)