Reported: clicking "Open Downloads folder" did nothing visible. The
previous implementation called ``os.startfile(folder)`` on Windows,
which is known to silently no-op or open Explorer behind the active
window in some configurations (Streamlit running headless, no
foreground rights inherited by the click handler thread, etc.).
Switch to the more reliable ``explorer /select,<file>`` form:
- Opens Explorer with the just-saved file pre-highlighted instead of
just navigating to the folder — better UX than the old behavior.
- explorer.exe is a real GUI process that's spawned in the user's
session with foreground rights, so it shows up on top.
- Fallback chain on Windows: ``/select`` first, then plain
``explorer <folder>``, then ``os.startfile`` as a last resort.
macOS upgraded the same way: ``open -R <file>`` reveals in Finder
rather than opening the directory.
Linux: no reliable cross-distro reveal, so ``xdg-open <folder>``.
Plus user feedback at the call site:
- On successful dispatch: ``st.toast("Opening <folder>", icon="📂")``
— confirms we tried, in case the window comes up behind the
browser.
- On dispatch failure: ``st.warning`` with the full path the user
can copy/paste into their file manager manually.
2220 tests pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Michael
0f89d7ba66