Fix: File with only comment and one on the first line reorder comments (#2955)

fix #2508

.chronus/changes/fix-comment-only-2024-1-26-16-20-24.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+[Formatter] Formatting file with only comments would reorder the first line.

packages/compiler/src/formatter/print/comment-handler.ts

@@ -1,8 +1,9 @@
 import type { Printer } from "prettier";
-import { Node, SyntaxKind, TypeSpecScriptNode } from "../../core/types.js";
+import { Node, SyntaxKind, TextRange, TypeSpecScriptNode } from "../../core/types.js";
 import { util } from "./util.js";
 
-interface CommentNode {
+interface CommentNode extends TextRange {
+  readonly kind: SyntaxKind.LineComment | SyntaxKind.BlockComment;
   precedingNode?: Node;
   enclosingNode?: Node;
   followingNode?: Node;
@@ -19,6 +20,14 @@ export const commentHandler: Printer<Node>["handleComments"] = {
       addCommentBetweenAnnotationsAndNode,
       handleOnlyComments,
     ].some((x) => x({ comment, text, options, ast: ast as TypeSpecScriptNode, isLastComment })),
+  remaining: (comment, text, options, ast, isLastComment) =>
+    [handleOnlyComments].some((x) =>
+      x({ comment, text, options, ast: ast as TypeSpecScriptNode, isLastComment })
+    ),
+  endOfLine: (comment, text, options, ast, isLastComment) =>
+    [handleOnlyComments].some((x) =>
+      x({ comment, text, options, ast: ast as TypeSpecScriptNode, isLastComment })
+    ),
 };
 
 interface CommentContext {

packages/compiler/test/formatter/formatter.test.ts

@@ -960,6 +960,22 @@ alias foo = ""; /* one */ /* two */ /* three */
       });
     });
 
+    it("format empty file with comment inside starting first line", async () => {
+      await assertFormat({
+        code: `
+  // empty file
+
+
+  // commented out things
+`,
+        expected: `
+// empty file
+
+// commented out things
+`,
+      });
+    });
+
     it("format empty model with comment inside", async () => {
       await assertFormat({
         code: `