Ansiconsole decorations are for a standard console window, not a script output pane like SQLDeveloper Worksheet Script output.
You can switch off ansiconsole on sqldeveloper worksheet as a workaround.
Please forgive me for bieng late.
These are not some kind of decorations. These are standard characters in french language (accentuated characters like é,è,à,...).
I want to use ansiconsole because it's the most suitable for my needs. It isn't acceptable that some characters supported by Oracle database aren't correctly displayed in SQL Developer.
Despite Barry's reply, the bug Dermot filed is still open without a clear statement on what the resolution will be. Of course, the goal is to have as much common code as possible between SQLcl and the worksheet, but apparently a difference exists in this case. Possibly some fix is already in for the upcoming 4.2 EA2. Let's hope.
Checking the 4.1.x SQL Developer releases with a test case in Spanish, I see set sqlformat ansiconsole has never worked for diacritcs in the script output of a worksheet. The same is true so far for the current 4.2 EA2 code base. Even in SQLcl, with a Windows system locale of Spanish(United States), it is necessary to change the code page from 850 to, say, 1250 (chcp 1250) to get the text (diacritics, euro symbol) to display properly.
I couldn't see the bug status, but I wanted to make clear that this wasn't about some decoration.
I tried SQLcl before and as you said, it is mandatory to change code page to display these characters properly. As it's a console-based software, this makes sense to me, but I thought that these restrictions didn't apply to SQL Developer. I don't know how is made script output, but it seems that, even if the underlying processing code is common between SQLcl and SQL Developer, SQL Developer lacks a way to set script output character set. (but there's no doubt you're way more aware of that than me)