feat: added error handler

Author: ntamas

src/codegen/internal_lib.py.in

@@ -35,6 +35,7 @@ from .types import (
     igraph_adjlist_t,
     igraph_arpack_options_t,
     igraph_bliss_info_t,
+    igraph_error_handler_t,
     igraph_hrg_t,
     igraph_layout_drl_options_t,
     igraph_maxflow_stats_t,
@@ -381,5 +382,11 @@ igraph_destroy = _lib.igraph_destroy
 igraph_destroy.restype = None
 igraph_destroy.argtypes = [POINTER(igraph_t)]
 
+# Error handling
+
+igraph_set_error_handler = _lib.igraph_set_error_handler
+igraph_set_error_handler.restype = igraph_error_handler_t
+igraph_set_error_handler.argtypes = [igraph_error_handler_t]
+
 # The rest of this file is generated by Stimulus
 

src/igraph_ctypes/_internal/errors.py

@@ -1,7 +1,15 @@
 from .types import igraph_error_t
 
+__all__ = ("handle_igraph_error_t",)
+
 
 def handle_igraph_error_t(code: igraph_error_t) -> None:
     """Handles the given igraph error code, raising exceptions appropriately."""
     if code:
-        raise RuntimeError(f"igraph returned error code {code}")
+        from .setup import _get_last_error_state
+
+        error_state = _get_last_error_state()
+        if error_state:
+            error_state.raise_error()
+        else:
+            raise RuntimeError(f"igraph returned error code {code}")

src/igraph_ctypes/_internal/lib.py

@@ -35,6 +35,7 @@
     igraph_adjlist_t,
     igraph_arpack_options_t,
     igraph_bliss_info_t,
+    igraph_error_handler_t,
     igraph_hrg_t,
     igraph_layout_drl_options_t,
     igraph_maxflow_stats_t,
@@ -381,6 +382,12 @@ def _load_igraph_c_library():
 igraph_destroy.restype = None
 igraph_destroy.argtypes = [POINTER(igraph_t)]
 
+# Error handling
+
+igraph_set_error_handler = _lib.igraph_set_error_handler
+igraph_set_error_handler.restype = igraph_error_handler_t
+igraph_set_error_handler.argtypes = [igraph_error_handler_t]
+
 # The rest of this file is generated by Stimulus
 
 # Set up aliases for all enum types

src/igraph_ctypes/_internal/setup.py

@@ -1,13 +1,99 @@
+from dataclasses import dataclass
+
+from .functions import igraph_strerror
+from .lib import igraph_set_error_handler
 from .rng import NumPyRNG
+from .types import igraph_error_t, igraph_error_handler_t
 
 __all__ = ("setup_igraph_library",)
 
 
-def setup_igraph_library() -> None:
-    """Initializes the random number generator of the igraph library.
+@dataclass
+class IgraphErrorState:
+    """Dataclass storing the details of the last error message received from
+    igraph.
+    """
 
-    This function is called when the ``igraph_ctypes`` module is imported by the user.
+    message: bytes = b""
+    filename: bytes = b""
+    line: int = 0
+    error: igraph_error_t = igraph_error_t(0)
+
+    def _error_handler(
+        self, message: bytes, filename: bytes, line: int, error: igraph_error_t
+    ):
+        self.message = message
+        self.filename = filename
+        self.line = line
+        self.error = error
+        print(repr(self))
+
+    @property
+    def has_error(self) -> bool:
+        """Returns whether the error state object currently stores an error."""
+        return int(self.error) != 0
+
+    def raise_error(self) -> None:
+        """Raises an appropriate Python exception if there is an error stored
+        in the state object. No-op otherwise.
+        """
+        code = int(self.error)
+
+        if code == 0:
+            return
+        elif code == 12:  # IGRAPH_UNIMPLEMENTED
+            exc = NotImplementedError
+        elif code == 2:  # IGRAPH_ENOMEM
+            exc = MemoryError
+        else:
+            exc = RuntimeError
+
+        msg = self.message
+        if msg and msg[-1] not in b".!?":
+            msg = msg + b"."
+
+        filename_str = self.filename.decode("utf-8", errors="replace")
+        message_str = msg.decode("utf-8", errors="replace")
+        error_code_str = igraph_strerror(self.error).decode("utf-8", errors="replace")
+
+        raise exc(
+            f"Error at {filename_str}:{self.line}: {message_str} -- {error_code_str}"
+        )
+
+
+_last_error = IgraphErrorState()
+
+
+@igraph_error_handler_t
+def _error_handler(message: bytes, filename: bytes, line: int, error: igraph_error_t):
+    global _last_error
+    _last_error._error_handler(message, filename, line, error)
+
+
+def _get_last_error_state() -> IgraphErrorState:
+    global _last_error
+    return _last_error
+
+
+def _setup_error_handler() -> None:
+    """Sets up the error handler needed to integrate igraph's error handling
+    nicely with Python.
     """
+    igraph_set_error_handler(_error_handler)
+
+
+def _setup_rng() -> None:
+    """Initializes the random number generator of the igraph library."""
     from numpy.random import default_rng
 
     NumPyRNG(default_rng()).attach()
+
+
+def setup_igraph_library() -> None:
+    """Integrates the facilities of the igraph library with Python.
+
+    This function is called when the ``igraph_ctypes`` module is imported by the user.
+    You should not need to call this function directly.
+    """
+    _setup_error_handler()
+    _setup_rng()

src/igraph_ctypes/_internal/types.py

@@ -409,6 +409,8 @@ class igraph_rng_t(Structure):
     ]
 
 
+igraph_error_handler_t = CFUNCTYPE(None, c_char_p, c_char_p, c_int, igraph_error_t)
+
 igraph_isocompat_t = CFUNCTYPE(
     igraph_bool_t,
     POINTER(igraph_t),

test/test_basic_interface.py

@@ -1,4 +1,5 @@
 from numpy import array
+from pytest import raises
 
 from igraph_ctypes._internal.enums import NeighborMode
 from igraph_ctypes.constructors import create_empty_graph
@@ -129,11 +130,8 @@ def test_get_eid_directed():
         assert g.get_edge_id((i + 1) % n, i, error=False) == -1
         assert g.get_edge_id((i + 1) % n, i, directed=False) == i
 
-        # TODO(ntamas): does not work yet, error handler must be implemented
-        """
-        with raises(match="no such edge"):
+        with raises(RuntimeError, match="no such edge"):
             assert g.get_edge_id((i + 1) % n, i) == i
-        """
 
 
 def test_get_eid_undirected():