JSDoc uses same newlines as normal scanner (#39351)

* JSDoc uses same newlines as normal scanner

Previously, scanJsDocToken treated each newline character separately, so
the sequence \r\n would be treated as two lines. This is unexpected, and
not the way the normal scanner does it.

This change makes the jsdoc scanner behave the same as the normal
scanner.

* fix lint in test

src/compiler/scanner.ts

@@ -2352,8 +2352,12 @@ namespace ts {
                     return token = SyntaxKind.WhitespaceTrivia;
                 case CharacterCodes.at:
                     return token = SyntaxKind.AtToken;
-                case CharacterCodes.lineFeed:
                 case CharacterCodes.carriageReturn:
+                    if (text.charCodeAt(pos) === CharacterCodes.lineFeed) {
+                        pos++;
+                    }
+                    // falls through
+                case CharacterCodes.lineFeed:
                     tokenFlags |= TokenFlags.PrecedingLineBreak;
                     return token = SyntaxKind.NewLineTrivia;
                 case CharacterCodes.asterisk:

src/testRunner/unittests/publicApi.ts

@@ -53,6 +53,24 @@ describe("unittests:: Public APIs:: createPrivateIdentifier", () => {
     });
 });
 
+describe("unittests:: Public APIs:: JSDoc newlines", () => {
+    it("are preserved verbatim", () => {
+        const testFilePath = "/file.ts";
+        const testFileText = `
+/**
+* @example
+* Some\n * text\r\n * with newlines.
+*/
+function test() {}`;
+
+        const testSourceFile = ts.createSourceFile(testFilePath, testFileText, ts.ScriptTarget.Latest, /*setParentNodes*/ true);
+        const funcDec = testSourceFile.statements.find(ts.isFunctionDeclaration)!;
+        const tags = ts.getJSDocTags(funcDec);
+        assert.isDefined(tags[0].comment);
+        assert.equal(tags[0].comment, "Some\n text\r\n with newlines.");
+    });
+});
+
 describe("unittests:: Public APIs:: isPropertyName", () => {
     it("checks if a PrivateIdentifier is a valid property name", () => {
         const prop = ts.factory.createPrivateIdentifier("#foo");