Include error message with error status

blender_asset_tracer/pack/transfer.py

@@ -70,7 +70,10 @@ class FileTransferer(threading.Thread, metaclass=abc.ABCMeta):
         self.queue = queue.PriorityQueue(maxsize=100)  # type: queue.PriorityQueue[QueueItem]
         self.done = threading.Event()
         self._abort = threading.Event()  # Indicates user-requested abort
-        self._error = threading.Event()  # Indicates abort due to some error
+
+        self.__error_mutex = threading.Lock()
+        self.__error = threading.Event()  # Indicates abort due to some error
+        self.__error_message = ''
 
         # Instantiate a dummy progress callback so that we can call it
         # without checking for None all the time.
@@ -86,7 +89,7 @@ class FileTransferer(threading.Thread, metaclass=abc.ABCMeta):
         """Queue a copy action from 'src' to 'dst'."""
         assert not self.done.is_set(), 'Queueing not allowed after done_and_join() was called'
         assert not self._abort.is_set(), 'Queueing not allowed after abort_and_join() was called'
-        if self._error.is_set():
+        if self.__error.is_set():
             return
         self.queue.put((src, dst, Action.COPY))
         self.total_queued_bytes += src.stat().st_size
@@ -95,7 +98,7 @@ class FileTransferer(threading.Thread, metaclass=abc.ABCMeta):
         """Queue a move action from 'src' to 'dst'."""
         assert not self.done.is_set(), 'Queueing not allowed after done_and_join() was called'
         assert not self._abort.is_set(), 'Queueing not allowed after abort_and_join() was called'
-        if self._error.is_set():
+        if self.__error.is_set():
             return
         self.queue.put((src, dst, Action.MOVE))
         self.total_queued_bytes += src.stat().st_size
@@ -156,7 +159,7 @@ class FileTransferer(threading.Thread, metaclass=abc.ABCMeta):
         """Generator, yield queued items until the work is done."""
 
         while True:
-            if self._abort.is_set() or self._error.is_set():
+            if self._abort.is_set() or self.__error.is_set():
                 return
 
             try:
@@ -197,4 +200,22 @@ class FileTransferer(threading.Thread, metaclass=abc.ABCMeta):
 
     @property
     def has_error(self) -> bool:
-        return self._error.is_set()
+        return self.__error.is_set()
+
+    def error_set(self, message: str):
+        """Indicate an error occurred, and provide a message."""
+
+        with self.__error_mutex:
+            # Avoid overwriting previous error messages.
+            if self.__error.is_set():
+                return
+
+            self.__error.set()
+            self.__error_message = message
+
+    def error_message(self) -> str:
+        """Retrieve the error messsage, or an empty string if no error occurred."""
+        with self.__error_mutex:
+            if not self.__error.is_set():
+                return ''
+            return self.__error_message