From 757c35e4a0d42c6bf53286981fb3191513d4242d Mon Sep 17 00:00:00 2001
From: funman300 <funman300@gmail.com>
Date: Tue, 7 Jul 2026 11:00:20 -0700
Subject: [PATCH] fix(engine): degrade gracefully when the platform data dir is
 missing
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user_theme_dir() panicked on desktop when dirs::data_dir() returned
None (broken $HOME / $XDG_*). Return an empty path instead — exactly
what the wasm32 branch already did — so theme discovery reports 'no
user themes' and the bundled default keeps working. Warns once with
the set_user_theme_dir() workaround. CLAUDE.md §2.3: no panic! in
runtime logic.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 solitaire_engine/src/assets/user_dir.rs | 51 +++++++++++++------------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/solitaire_engine/src/assets/user_dir.rs b/solitaire_engine/src/assets/user_dir.rs
index 020116a..4db9637 100644
--- a/solitaire_engine/src/assets/user_dir.rs
+++ b/solitaire_engine/src/assets/user_dir.rs
@@ -53,12 +53,12 @@ pub fn set_user_theme_dir(path: PathBuf) -> Result<(), PathBuf> {
 /// Returns the absolute path of the user-themes directory on the
 /// current platform.
 ///
-/// # Panics
-///
-/// Panics if [`solitaire_data::data_dir`] returns `None`, which on
-/// desktop indicates a broken `$HOME` / `$XDG_*` configuration.
-/// Android always returns `Some`. The panic message names the
-/// supported workaround ([`set_user_theme_dir`]).
+/// When [`solitaire_data::data_dir`] returns `None` (broken `$HOME` /
+/// `$XDG_*` on desktop; always on wasm32, which has no filesystem) this
+/// returns an empty path — callers treat that as "no user themes" and
+/// the bundled default theme still works. A warning naming the
+/// [`set_user_theme_dir`] workaround is logged once. Android always
+/// resolves.
 pub fn user_theme_dir() -> PathBuf {
     if let Some(p) = USER_THEME_DIR_OVERRIDE.get() {
         return p.clone();
@@ -76,29 +76,32 @@ fn user_theme_dir_for(data_dir: PathBuf) -> PathBuf {
 /// Per-target-os resolution of the platform's data dir. Delegates
 /// to [`solitaire_data::data_dir`] which encapsulates the
 /// per-target shape (desktop: `dirs::data_dir()`; android: the
-/// hardcoded `/data/data/<package>/files` sandbox path). Panics
-/// only when the underlying resolver returns `None`, which on
-/// desktop indicates a broken `$HOME` / `$XDG_*` configuration —
-/// the panic message names the supported workaround.
+/// hardcoded `/data/data/<package>/files` sandbox path).
+///
+/// When the resolver returns `None` — always on wasm32 (no
+/// filesystem), or a broken `$HOME` / `$XDG_*` configuration on
+/// desktop — this degrades to an empty path, which downstream theme
+/// scanning treats as "no user themes"; the bundled default theme is
+/// unaffected. CLAUDE.md §2.3 forbids panicking here: losing custom
+/// themes must not take the whole game down with it.
 fn detected_platform_data_dir() -> PathBuf {
     solitaire_data::data_dir().unwrap_or_else(|| {
-        // On wasm32, data_dir() always returns None — there is no filesystem.
-        // User themes are not supported in the browser build; return an empty
-        // path so callers produce a benign empty dir rather than panicking.
-        #[cfg(target_arch = "wasm32")]
-        {
-            PathBuf::new()
-        }
         #[cfg(not(target_arch = "wasm32"))]
         {
-            panic!(
-                "user_theme_dir(): platform data directory is unavailable. \
-                 On Linux check $XDG_DATA_HOME or $HOME; on macOS / Windows \
-                 the OS reported no Application Support / AppData path. \
-                 As a workaround call solitaire_engine::assets::user_dir::\
-                 set_user_theme_dir() before App::run()."
-            )
+            use std::sync::Once;
+            static WARN_ONCE: Once = Once::new();
+            WARN_ONCE.call_once(|| {
+                bevy::log::warn!(
+                    "user_theme_dir(): platform data directory is unavailable; \
+                     user themes are disabled. On Linux check $XDG_DATA_HOME or \
+                     $HOME; on macOS / Windows the OS reported no Application \
+                     Support / AppData path. As a workaround call \
+                     solitaire_engine::assets::user_dir::set_user_theme_dir() \
+                     before App::run()."
+                );
+            });
         }
+        PathBuf::new()
     })
 }