yas-new-snippet always duplicates the selected input. What might be causing it?

Question

I've experienced this issue for some time. It's not a blocker but it is a bit annoying.

Steps to reproduce:

Select a region that you want to extract into YASnippet snippet("foo bar"). Eval yas-new-snippet.

You are redirected to a new buffer +new-snippet+ with the following content:

# -*- mode: snippet -*-
# name: 
# key: 
# --
// foo bar
// foo bar

Expected behavior:

# -*- mode: snippet -*-
# name: 
# key: 
# --
// foo bar

pkg-info-package-version yasnippet 20200604.246

Answer 1

You have probably set yas-wrap-around-region to t, this will insert your region at the snippet placeholder $0. Calling yas-new-snippet will expand a snippet to create your new snippet: yas-new-snippet-default. If you look at the default value, it contains $0 and yas-selected-text, and now both will be filled with your region.

I suggested a fix in this PR: https://github.com/joaotavora/yasnippet/pull/1102

As a workaround, you could advice the function like this:

(defun yas-new-snippet-fix-region (func &rest args)
  (let ((yas-wrap-around-region nil))
    (apply func args)))
(advice-add 'yas-new-snippet :around #'yas-new-snippet-fix-region)