Stop mutate doc.parts when printing fill (#13315)

Co-authored-by: Alexander Kachkaev <alexander@kachkaev.ru>

tests/unit/doc-printer.js

@@ -0,0 +1,45 @@
+// TODO: Find a better way to test the performance
+import { fill, join, line } from "../../src/document/builders.js";
+import { printDocToString } from "../../src/document/printer.js";
+
+test("`printDocToString` should not manipulate docs", () => {
+  const printOptions = { printWidth: 40, tabWidth: 2 };
+  const doc = fill(
+    join(
+      line,
+      Array.from({ length: 255 }, (_, index) => String(index + 1)),
+    ),
+  );
+
+  expect(doc.parts.length).toBe(255 + 254);
+
+  const { formatted: firstPrint } = printDocToString(doc, printOptions);
+
+  expect(doc.parts.length).toBe(255 + 254);
+
+  const { formatted: secondPrint } = printDocToString(doc, printOptions);
+
+  expect(firstPrint).toBe(secondPrint);
+
+  {
+    // About 1000 lines, #3263
+    const WORD = "word";
+    const hugeParts = join(
+      line,
+      Array.from(
+        { length: 1000 * Math.ceil(printOptions.printWidth / WORD.length) },
+        () => WORD,
+      ),
+    );
+    const orignalLength = hugeParts.length;
+
+    const startTime = performance.now();
+    const { formatted } = printDocToString(fill(hugeParts), printOptions);
+    const endTime = performance.now();
+    expect(hugeParts.length).toBe(orignalLength);
+
+    const lines = formatted.split("\n");
+    expect(lines.length).toBeGreaterThan(1000);
+    expect(endTime - startTime).toBeLessThan(1000);
+  }
+});