fix: Improve error clearing (#184)

* fix: CLean up errors

* fix: Error cleanup on isntantiate/new use

* fix: Clarify comment

Author: tmathern

src/c2pa/c2pa.py

@@ -244,6 +244,19 @@ class C2paStream(ctypes.Structure):
     ]
 
 
+def _clear_error_state():
+    """Clear any existing error state from the C library.
+
+    This function should be called at the beginning of object initialization
+    and before any operations that could potentially raise an error,
+    to ensure that stale error states from previous operations don't interfere
+    with new objects being created, or independent function calls.
+    """
+    error = _lib.c2pa_error()
+    if error:
+        # Free the error to clear the state
+        _lib.c2pa_string_free(error)
+
 class C2paSignerInfo(ctypes.Structure):
     """Configuration for a Signer."""
     _fields_ = [
@@ -264,6 +277,7 @@ def __init__(self, alg, sign_cert, private_key, ta_url):
             private_key: The private key as a string
             ta_url: The timestamp authority URL as bytes
         """
+        _clear_error_state()
 
         if sign_cert is None:
             raise ValueError("sign_cert must be set")
@@ -692,6 +706,8 @@ def load_settings(settings: Union[str, dict], format: str = "json") -> None:
     Raises:
         C2paError: If there was an error loading the settings
     """
+    _clear_error_state()
+
     # Convert to JSON string as necessary
     try:
         if isinstance(settings, dict):
@@ -776,6 +792,8 @@ def read_ingredient_file(
         stacklevel=2,
     )
 
+    _clear_error_state()
+
     container = _StringContainer()
 
     container._path_str = str(path).encode('utf-8')
@@ -821,6 +839,8 @@ def read_file(path: Union[str, Path],
         stacklevel=2,
     )
 
+    _clear_error_state()
+
     container = _StringContainer()
 
     container._path_str = str(path).encode('utf-8')
@@ -907,6 +927,8 @@ def sign_file(
         stacklevel=2,
     )
 
+    _clear_error_state()
+
     try:
         # Determine if we have a signer or signer info
         if isinstance(signer_or_info, C2paSignerInfo):
@@ -1375,6 +1397,9 @@ def __init__(self,
             C2paError.Encoding: If any of the string inputs
               contain invalid UTF-8 characters
         """
+        # Native libs plumbing:
+        # Clear any stale error state from previous operations
+        _clear_error_state()
 
         self._closed = False
         self._initialized = False
@@ -1930,6 +1955,10 @@ def from_info(cls, signer_info: C2paSignerInfo) -> 'Signer':
         Raises:
             C2paError: If there was an error creating the signer
         """
+        # Native libs plumbing:
+        # Clear any stale error state from previous operations
+        _clear_error_state()
+
         signer_ptr = _lib.c2pa_signer_from_info(ctypes.byref(signer_info))
 
         if not signer_ptr:
@@ -2055,6 +2084,10 @@ def wrapped_callback(
                 cls._ERROR_MESSAGES['encoding_error'].format(
                     str(e)))
 
+        # Native libs plumbing:
+        # Clear any stale error state from previous operations
+        _clear_error_state()
+
         # Create the callback object using the callback function
         callback_cb = SignerCallback(wrapped_callback)
 
@@ -2095,6 +2128,10 @@ def __init__(self, signer_ptr: ctypes.POINTER(C2paSigner)):
         Raises:
             C2paError: If the signer pointer is invalid
         """
+        # Native libs plumbing:
+        # Clear any stale error state from previous operations
+        _clear_error_state()
+
         # Validate pointer before assignment
         if not signer_ptr:
             raise C2paError("Invalid signer pointer: pointer is null")
@@ -2327,6 +2364,7 @@ def from_archive(cls, stream: Any) -> 'Builder':
         """
         builder = cls({})
         stream_obj = Stream(stream)
+
         builder._builder = _lib.c2pa_builder_from_archive(stream_obj._stream)
 
         if not builder._builder:
@@ -2352,6 +2390,10 @@ def __init__(self, manifest_json: Any):
             C2paError.Encoding: If manifest JSON contains invalid UTF-8 chars
             C2paError.Json: If the manifest JSON cannot be serialized
         """
+        # Native libs plumbing:
+        # Clear any stale error state from previous operations
+        _clear_error_state()
+
         self._closed = False
         self._initialized = False
         self._builder = None
@@ -2884,6 +2926,8 @@ def format_embeddable(format: str, manifest_bytes: bytes) -> tuple[int, bytes]:
     Raises:
         C2paError: If there was an error converting the manifest
     """
+    _clear_error_state()
+
     format_str = format.encode('utf-8')
     manifest_array = (ctypes.c_ubyte * len(manifest_bytes))(*manifest_bytes)
     result_bytes_ptr = ctypes.POINTER(ctypes.c_ubyte)()
@@ -2993,6 +3037,8 @@ def ed25519_sign(data: bytes, private_key: str) -> bytes:
         C2paError: If there was an error signing the data
         C2paError.Encoding: If the private key contains invalid UTF-8 chars
     """
+    _clear_error_state()
+
     if not data:
         raise C2paError("Data to sign cannot be empty")