Audacity fails to parse “~” tilde for user’s home directory in export audio dialog

[InconsolableCellist]

Bug description

Problem Description:
When exporting audio, Audacity fails to interpret the “~” tilde on Linux, which should expand to the user’s home ($HOME) directory.

Steps to reproduce

Steps to reproduce:

1. Open Audacity
2. Create some audio (e.g., generate 440 Hz sine wave for 1 second)
3. Select All
4. Click File-> Export Audio
5. In the “Folder” field in the dialog box that pops up, enter “~/somedir”
6. (optional?) set “WAV (Microsoft)”, Mono, 44100 Hz, Signed 16-bit PCM, Entire Project
7. Click Export

Expected behavior

Expected Behavior
The file should be saved in $HOME/somedir/untitled.wav. The “~” needs to expand to the home directory.

Actual behavior

Observed Behavior
The file will be saved in $HOME/~/somedir/untitled.wav. Note the inclusion of the string literal “~” in the path. $HOME refers to the environment variable where the user’s home directory is, usually something like /home/user/

Audacity Version

latest stable version (from audacityteam.org/download)

Operating system

Linux

Additional context

Environment
Artix Linux
Audacity 3.5.1
KDE Plasma 6

Other
This also invites disaster for an unsuspecting user, who might attempt to rm -rf the errant “~” directory and could end up with a very bad day

[rbdannenberg]

I'm pretty sure ~ is interpreted by the shell, and file IO primitives including system commands like open do not do regular expression matching or convert ~ to $HOME or replace $HOME for that matter. So you could actually name a file "~" or "$HOME" although it's obviously a bad idea.

[InconsolableCellist]

All GTK+ file pickers/choosers, Qt, KDE, and all popular desktop applications support "~" expansion.

E.g., right click this page in Firefox or Chrome, type ~/somefile.txt and it'll save it in $HOME/somefile.txt.

Shells do also expand ~ but it isn't limited to a shell feature

[InconsolableCellist]

According to a comment in the forum (https://forum.audacityteam.org/t/bug-audacity-fails-to-parse-tilde-for-users-home-directory-in-export-audio-dialog/106141) this may be a regression after 3.4.2

[LWinterberg]

It's not technically a regression - before 3.4, the export dialog was a customized file picker. Now, the "browse" button in the export dialog opens the native (and unmodified) file picker, while the box inside the export dialog just is a textbox.

A fix for this probably involves validating mFullName in ExportFilePanel.cpp. There already is ExportFilePanel::ValidateAndFixExt() which does the same for invalid characters in the filename.