JavaScript AST inconsistent about trivia vs JSDoc

[evmar]

The parsed JavaScript AST sometimes includes JSDoc in its trivia, and sometimes it doesn't. This seems to be a regression from TS 1.9ish to current tip of tree.

If you have an input file like

/** @a */
var a = 3;
/** @b */
function b() { }

and you parse this with TypeScript ts.createSourceFile and reserialize it out via a recursive loop like:

function dump(node: ts.Node) {
  let pos = node.getFullStart();
  for (const child of node.getChildren()) {
    dumpRange(pos, child.getFullStart());
    dump(child);
    pos = child.getEnd();
  }
  dumpRange(pos, node.getEnd());

  function dumpRange(start: number, end: number) {
    process.stdout.write(node.getSourceFile().text.slice(start, end));
  }
}

The output is:

/** @a *//** @a */
var a = 3;
/** @b */
function b() { }

You'll see that one of the comments was duplicated, and the other wasn't.

I think this is because in the FunctionDeclaration case, the trivia of the FunctionDeclaration node stops at the JSDocComment, but in the VariableStatement case, the trivia of the VarKeyword still includes the jsdoc despite it also having a JSDocComment.

[evmar]

(If it'd be helpful, I have a small program I can upload somewhere that does the AST dumping I mentioned.)

[evmar]

I think the underlying cause of this is using node.getChildren() rather than ts.forEachChild.

It appears the former actually re-parses the source code and it produces bad parses in this case and in other cases (angular/tsickle@c410541 )

[typescript-bot]

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