From ea2c831b01152a3b401cab3ef1d31d6fa6489ba7 Mon Sep 17 00:00:00 2001
From: David Foster <david@dafoster.net>
Date: Mon, 8 Jan 2024 10:21:05 -0500
Subject: [PATCH] Shell: Fix race condition where shell might start accepting
 commands before foreground thread created

---
 src/crystal/main.py  | 14 +++++++-------
 src/crystal/shell.py |  3 +++
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/crystal/main.py b/src/crystal/main.py
index 1753dba1..430afa6e 100644
--- a/src/crystal/main.py
+++ b/src/crystal/main.py
@@ -189,13 +189,6 @@ def _main(args: List[str]) -> None:
         install_to_linux_desktop_environment()
         sys.exit()
     
-    # Start shell if requested
-    if parsed_args.shell:
-        from crystal.shell import Shell
-        shell = Shell()
-    else:
-        shell = None
-    
     # Start GUI subsystem
     import wx
     import wx.xml  # required by wx.richtext; use explicit import as hint to py2app
@@ -293,6 +286,13 @@ def _finish_launch(self, filepath: Optional[str]=None) -> None:
     from crystal.util.xthreading import is_quitting, set_foreground_thread
     set_foreground_thread(threading.current_thread())
     try:
+        # Start shell if requested
+        if parsed_args.shell:
+            from crystal.shell import Shell
+            shell = Shell()
+        else:
+            shell = None
+        
         app = MyApp(redirect=False)
         
         # Starts tests if requested
diff --git a/src/crystal/shell.py b/src/crystal/shell.py
index 174e34cc..ce131ee8 100644
--- a/src/crystal/shell.py
+++ b/src/crystal/shell.py
@@ -17,6 +17,9 @@
 
 class Shell:
     def __init__(self) -> None:
+        if not has_foreground_thread():
+            raise ValueError('Expected there to be a foreground thread when starting a Shell')
+        
         # Setup proxy variables for shell
         _Proxy._patch_help()
         self._project_proxy = _Proxy(f'<unset {Project.__module__}.{Project.__name__} proxy>')