fix: fix trailing comment on empty spec

src/prettier/print-abstract-node.ts

@@ -204,7 +204,6 @@ export function printAbstractNode(
   }
 
   const trailingTriviaDoc = getTrailingTriviaDoc(node);
-
   if (trailingTriviaDoc) {
     // prevent extra lines at end of specification
     if (

src/prettier/util/print-utils.ts

@@ -85,6 +85,10 @@ export function addTrailingTriviaDoc(
 ): Doc {
   if (Array.isArray(doc)) {
     if (doc.length === 0) {
+      doc = [
+        trailingTriviaDoc,
+      ];
+
       return doc;
     }
 

tests/prettier/print-specification.test.ts

@@ -43,4 +43,12 @@ describe("Print Specification tests", () => {
       "§\n",
     );
   });
+
+  test("prettified specification output is as expected for only a comment", async () => {
+    await testPrettierScenario(
+      "// Start typing your SDL here... <Ctrl+Space> for completions\n",
+      "// Start typing your SDL here... <Ctrl+Space> for completions\n",
+      "// Start typing your SDL here... <Ctrl+Space> for completions\n",
+    );
+  });
 });

tests/prettier/util/print-utils.test.ts

@@ -506,6 +506,20 @@ describe("Print Utils tests", () => {
       ifBreak([line, ""], " "),
       ["// hello", hardline],
     ]], hardline], hardline]);
+
+    docs = [["class", "A", ["}"], hardline], hardline];
+    docs = addTrailingTriviaDoc(docs, trailingTriviaDoc);
+    expect(docs).toEqual([["class", "A", [[
+      "}",
+      ifBreak([line, ""], " "),
+      ["// hello", hardline],
+    ]], hardline], hardline]);
+
+    docs = [[]];
+    docs = addTrailingTriviaDoc(docs, trailingTriviaDoc);
+    expect(docs).toEqual([[
+      ["// hello", hardline],
+    ]]);
   });
 
   test("no trivia comment", async () => {