How to skip child nodes

Code:

var traverse = require("@babel/traverse").default;
var parser = require("@babel/parser");
var generate = require("@babel/generator").default;
var types = require("@babel/types");

var ast = parser.parse('{"abc";"123";}');
traverse(ast, {
  BlockStatement(path) {
    var p = path.get("body")[0];
    console.log("before", p.shouldSkip);
    p.skip();
    console.log("after", p.shouldSkip, path.get("body")[0].shouldSkip);
  },
  ExpressionStatement(path) {
    console.log(generate(path.node).code);
  }
});

return;

Output:

before false
after true false
"abc";
"123";

[nicolo-ribaudo]

This is definitely a bug. If you try to run this code in the monorepo:

const load = n => require(`./packages/babel-${n}`);
const babel = load("core");
const parser = load("parser");
const traverse = load("traverse").default;
const generate = load("generator").default;

const ast = parser.parse('{"abc";"123";}');
traverse(ast, {
  BlockStatement(path) {
    const p = path.get("body")[0];
    console.log("before", p.shouldSkip, path.get("body")[0] === p);
    p.skip();

    console.log("after 1", p.shouldSkip);
    path.get("body");
    console.log("after 2", p.shouldSkip);
  },
  ExpressionStatement(path) {
    console.log(generate(path.node).code);
  },
});

It will log after 1 true, after 1 false, but shouldSkip shouldn’t change from after 1 to after2.

[Domiii]

Skipping just does not work in general. Flags always get wiped before a visit, even without calling path.get in between:

Order of events

1. Before some p gets visited, I call p.skip(). That in turn sets NodePath._traverseFlags
2. Before p gets visited, setContext is called. Stacktrace looks like so:

   at NodePath.setContext (code\node_modules\@babel\traverse\lib\path\context.js:143:13)
   at NodePath.pushContext (code\node_modules\@babel\traverse\lib\path\context.js:219:8)
   at TraversalContext.visitQueue (code\node_modules\@babel\traverse\lib\context.js:89:14)
   at TraversalContext.visitSingle (code\node_modules\@babel\traverse\lib\context.js:73:19)
   at TraversalContext.visit (code\node_modules\@babel\traverse\lib\context.js:127:19)
   ...
   

3. setContext unconditionally unsets _traverseFlags
4. Skipped node still gets visited.

Thus skip will not work.

The only situation where skip can work is a partial skip; that is if you skip the node itself during its own enter call. In that case, enter was called but exit will not be called.

At this point I would like to ask point that it has been quite a while. Is there any news on this? NodePath.skip being straight-up broken looks quite bad. I know there are workarounds, but this is just a pretty obvious bug that requires fixing, if not at least acknowledgement.