ENH: register custom error handler to suppress printing error messages to stderr (#236)

Author: jorisvandenbossche

CHANGES.md

@@ -12,6 +12,8 @@
     specifying a mask manually for missing values in `write` (#219)
 -   Standardized 3-dimensional geometry type labels from "2.5D <type>" to
     "<type> Z" for consistency with well-known text (WKT) formats (#234)
+-   Failure error messages from GDAL are no longer printed to stderr (they were
+    already translated into Python exceptions as well) (#236).
 
 ## 0.5.1 (2023-01-26)
 

pyogrio/_err.pyx

@@ -3,7 +3,8 @@ from enum import IntEnum
 
 from pyogrio._ogr cimport (
     CE_None, CE_Debug, CE_Warning, CE_Failure, CE_Fatal, CPLErrorReset,
-    CPLGetLastErrorType, CPLGetLastErrorNo, CPLGetLastErrorMsg, OGRErr)
+    CPLGetLastErrorType, CPLGetLastErrorNo, CPLGetLastErrorMsg, OGRErr,
+    CPLErr, CPLErrorHandler, CPLDefaultErrorHandler, CPLPushErrorHandler)
 
 
 # CPL Error types as an enum.
@@ -207,3 +208,31 @@ cdef int exc_wrap_ogrerr(int err) except -1:
         raise CPLE_BaseError(3, err, f"OGR Error code {err}")
 
     return err
+
+
+cdef void error_handler(CPLErr err_class, int err_no, const char* err_msg) nogil:
+    """Custom CPL error handler to match the Python behaviour.
+
+    Generally we want to suppress error printing to stderr (behaviour of the
+    default GDAL error handler) because we already raise a Python exception
+    that includes the error message.
+    """
+    if err_class == CE_Fatal:
+        # If the error class is CE_Fatal, we want to have a message issued
+        # because the CPL support code does an abort() before any exception
+        # can be generated
+        CPLDefaultErrorHandler(err_class, err_no, err_msg)
+        return
+
+    elif err_class == CE_Failure:
+        # For Failures, do nothing as those are explicitly caught
+        # with error return codes and translated into Python exceptions
+        return
+
+    # Fall back to the default handler for non-failure messages since
+    # they won't be translated into exceptions.
+    CPLDefaultErrorHandler(err_class, err_no, err_msg)
+
+
+def _register_error_handler():
+    CPLPushErrorHandler(<CPLErrorHandler>error_handler)

pyogrio/_ogr.pxd

@@ -14,7 +14,7 @@ cdef extern from "cpl_conv.h":
     void        CPLSetConfigOption(const char* key, const char* value)
 
 
-cdef extern from "cpl_error.h":
+cdef extern from "cpl_error.h" nogil:
     ctypedef enum CPLErr:
         CE_None
         CE_Debug
@@ -27,6 +27,11 @@ cdef extern from "cpl_error.h":
     const char*    CPLGetLastErrorMsg()
     int             CPLGetLastErrorType()
 
+    ctypedef void (*CPLErrorHandler)(CPLErr, int, const char*)
+    void CPLDefaultErrorHandler(CPLErr, int, const char *)
+    void CPLPushErrorHandler(CPLErrorHandler handler)
+    void CPLPopErrorHandler()
+
 
 cdef extern from "cpl_string.h":
     char**      CSLAddNameValue(char **list, const char *name, const char *value)

pyogrio/core.py

@@ -17,11 +17,13 @@
         remove_virtual_file,
         _register_drivers,
     )
+    from pyogrio._err import _register_error_handler
     from pyogrio._io import ogr_list_layers, ogr_read_bounds, ogr_read_info
 
     _init_gdal_data()
     _init_proj_data()
     _register_drivers()
+    _register_error_handler()
 
     __gdal_version__ = get_gdal_version()
     __gdal_version_string__ = get_gdal_version_string()

pyogrio/tests/test_core.py

@@ -12,6 +12,7 @@
     get_gdal_config_option,
     get_gdal_data_path,
 )
+from pyogrio.errors import DataSourceError
 
 from pyogrio._env import GDALEnv
 
@@ -288,3 +289,12 @@ def test_reset_config_options():
 
     set_gdal_config_options({"foo": None})
     assert get_gdal_config_option("foo") is None
+
+
+def test_error_handling(capfd):
+    # an operation that triggers a GDAL Failure
+    # -> error translated into Python exception + not printed to stderr
+    with pytest.raises(DataSourceError, match="No such file or directory"):
+        read_info("non-existent.shp")
+
+    assert capfd.readouterr().err == ""