580 error messages from python plugins (#585)

# Description
Improves changes in PR #584 when addressing issue #580. 
Error messages from within Python plugins are now properly showed. The
error type is also shown.

## Type of change
- [x] Bug fix
- [x] New feature
- [ ] Documentation update
- [ ] Test update

## Checklist for the reviewer
This checklist should be used as a help for the reviewer.

- [ ] Is the change limited to one issue?
- [ ] Does this PR close the issue?
- [ ] Is the code easy to read and understand?
- [ ] Do all new feature have an accompanying new test?
- [ ] Has the documentation been updated as necessary?

bindings/python/dlite-python.i

@@ -25,9 +25,11 @@
      count. */
   PyObject *dlite_swig_exception = NULL;
 
-  /* forward declarations */
+  /* Global DLite exceptions - they will be initialised in %init */
   static PyObject *DLiteError = NULL;
   static PyObject *DLiteVerifyError = NULL;
+
+  /* forward declarations */
   char *strndup(const char *s, size_t n);
 %}
 

bindings/python/tests/test_entity.py

@@ -153,7 +153,7 @@
     entity = dlite.Instance.from_json(json_repr)
 except dlite.DLiteError as exc:
     assert str(exc) == (
-        "Error 1: metadata does not confirm to schema, please check "
+        "DLiteOtherError: metadata does not confirm to schema, please check "
         "dimensions, properties and/or relations: "
         "http://onto-ns.com/ex/0.1/test"
     )

src/dlite-errors.c

@@ -7,35 +7,35 @@
 const char *dlite_errname(DLiteErrors code)
 {
   switch (code) {
-  case dliteSuccess:                return "Sussess";
-  case dliteUnknownError:           return "UnknownError";
-  case dliteIOError:                return "IOError";
-  case dliteRuntimeError:           return "RuntimeError";
-  case dliteIndexError:             return "IndexError";
-  case dliteTypeError:              return "TypeError";
-  case dliteDivisionByZero:         return "DivisionByZero";
-  case dliteOverflowError:          return "OverflowError";
-  case dliteSyntaxError:            return "SyntaxError";
-  case dliteValueError:             return "ValueError";
-  case dliteSystemError:            return "SystemError";
-  case dliteAttributeError:         return "AttributeError";
-  case dliteMemoryError:            return "MemoryError";
-  case dliteNullReferenceError:     return "NullReferenceError";
+  case dliteSuccess:                return "DLiteSussess";
+  case dliteUnknownError:           return "DLiteUnknown";
+  case dliteIOError:                return "DLiteIO";
+  case dliteRuntimeError:           return "DLiteRuntime";
+  case dliteIndexError:             return "DLiteIndex";
+  case dliteTypeError:              return "DLiteType";
+  case dliteDivisionByZero:         return "DLiteDivisionByZero";
+  case dliteOverflowError:          return "DLiteOverflow";
+  case dliteSyntaxError:            return "DLiteSyntax";
+  case dliteValueError:             return "DLiteValue";
+  case dliteSystemError:            return "DLiteSystem";
+  case dliteAttributeError:         return "DLiteAttribute";
+  case dliteMemoryError:            return "DLiteMemory";
+  case dliteNullReferenceError:     return "DLiteNullReference";
 
-  case dliteKeyError:               return "KeyError";
-  case dliteParseError:             return "ParseError";
-  case dlitePrintError:             return "PrintError";
-  case dliteUnsupportedError:       return "UnsupportedError";
-  case dliteInconsistentDataError:  return "InconsistentDataError";
-  case dliteStorageOpenError:       return "StorageOpenError";
-  case dliteStorageLoadError:       return "StorageLoadError";
-  case dliteStorageSaveError:       return "StorageSaveError";
-  case dliteMissingInstanceError:   return "MissingInstanceError";
-  case dliteMissingMetadataError:   return "MissingMetadataError";
-  case dliteMetadataExistError:     return "MetadataExistError";
+  case dliteKeyError:               return "DLiteKey";
+  case dliteParseError:             return "DLiteParse";
+  case dlitePrintError:             return "DLitePrint";
+  case dliteUnsupportedError:       return "DLiteUnsupported";
+  case dliteInconsistentDataError:  return "DLiteInconsistentData";
+  case dliteStorageOpenError:       return "DLiteStorageOpen";
+  case dliteStorageLoadError:       return "DLiteStorageLoad";
+  case dliteStorageSaveError:       return "DLiteStorageSave";
+  case dliteMissingInstanceError:   return "DLiteMissingInstance";
+  case dliteMissingMetadataError:   return "DLiteMissingMetadata";
+  case dliteMetadataExistError:     return "DLiteMetadataExist";
 
-  case dliteLastError:              return "LastError";
+  case dliteLastError:              return "DLiteLast";
   }
-  if (code < 0) return "UndefinedError";
-  return "Successful";
+  if (code < 0) return "DLiteUndefined";
+  return "DLiteOther";
 }

src/dlite-misc.c

@@ -519,6 +519,15 @@ void dlite_globals_set(DLiteGlobals *globals_handler)
     err_set_state(g);
 }
 
+
+/* Error handler for DLite. */
+static void dlite_err_handler(const ErrRecord *record)
+{
+  FILE *stream = err_get_stream();
+  if (stream) fprintf(stream, "** %s\n", record->msg);
+}
+
+
 /*
   Initialises dlite. This function may be called several times.
  */
@@ -532,8 +541,11 @@ void dlite_init(void)
     /* Set up global state for utils/err.c */
     if (!dlite_globals_get_state(ERR_STATE_ID))
       dlite_globals_add_state(ERR_STATE_ID, err_get_state(), NULL);
-  }
 
+    /* Set up error handling */
+    err_set_handler(dlite_err_handler);
+    err_set_nameconv(dlite_errname);
+  }
 }
 
 

src/pyembed/dlite-pyembed.c

@@ -9,6 +9,8 @@
 #include "dlite-python-singletons.h"
 #include "config-paths.h"
 
+#define GLOBALS_ID "dlite-pyembed-globals"
+
 /* Get rid of MSVS warnings */
 #if defined WIN32 || defined _WIN32 || defined __WIN32__
 # pragma warning(disable: 4273 4996)
@@ -17,6 +19,67 @@
 
 static int python_initialized = 0;
 
+
+/* Struct correlating Python exceptions with DLite errors */
+typedef struct {
+  PyObject *exc;        /* Python exception */
+  DLiteErrors errcode;  /* DLite error */
+} ErrorCorrelation;
+
+/* Global state for this module */
+typedef struct {
+  ErrorCorrelation *errcorr;  /* NULL-terminated array */
+} PyembedGlobals;
+
+
+/* Free global state for this module */
+static void free_globals(void *globals)
+{
+  PyembedGlobals *g = (PyembedGlobals *)globals;;
+  if (g->errcorr) free(g->errcorr);
+  free(g);
+}
+
+/* Return a pointer to global state for this module */
+static PyembedGlobals *get_globals(void)
+{
+  PyembedGlobals *g = dlite_globals_get_state(GLOBALS_ID);
+  if (!g) {
+    if (!(g = calloc(1, sizeof(PyembedGlobals))))
+      return dlite_err(dliteMemoryError, "allocation failure"), NULL;
+    dlite_globals_add_state(GLOBALS_ID, g, free_globals);
+  }
+  return g;
+}
+
+/* Help function returning a constant pointer to a NULL-terminated
+   array of ErrorCorrelation records. */
+static const ErrorCorrelation *error_correlations(void)
+{
+  PyembedGlobals *g = get_globals();
+  if (!g->errcorr) {
+    ErrorCorrelation corr[] = {
+      {PyExc_KeyError, dliteKeyError},
+      {PyExc_MemoryError, dliteMemoryError},
+      {PyExc_AttributeError, dliteAttributeError},
+      {PyExc_SystemError, dliteSystemError},
+      {PyExc_ValueError, dliteValueError},
+      {PyExc_SyntaxError, dliteSyntaxError},
+      {PyExc_OverflowError, dliteOverflowError},
+      {PyExc_ZeroDivisionError, dliteDivisionByZero},
+      {PyExc_TypeError, dliteTypeError},
+      {PyExc_IndexError, dliteIndexError},
+      {PyExc_RuntimeError, dliteRuntimeError},
+      {PyExc_IOError, dliteIOError},
+      {NULL, 0}
+    };
+    if (!(g->errcorr = malloc(sizeof(corr))))
+      return dlite_err(dliteMemoryError, "allocation failure"), NULL;
+    memcpy(g->errcorr, corr, sizeof(corr));
+  }
+  return g->errcorr;
+}
+
 /* Initialises the embedded Python environment. */
 void dlite_pyembed_initialise(void)
 {
@@ -112,7 +175,6 @@ int dlite_pyembed_finalise(void)
   return status;
 }
 
-
 /*
   Returns a static pointer to the class name of python object cls or
   NULL on error.
@@ -130,6 +192,37 @@ const char *dlite_pyembed_classname(PyObject *cls)
 }
 
 
+/*
+  Return DLite error code given Python exception type.
+ */
+DLiteErrors dlite_pyembed_errcode(PyObject *type)
+{
+  const ErrorCorrelation *corr = error_correlations();
+  if (!type) return dliteSuccess;
+  while (corr->exc) {
+    if (PyErr_GivenExceptionMatches(type, corr->exc))
+      return corr->errcode;
+    corr++;
+  }
+  return dliteUnknownError;
+}
+
+/*
+  Return Python exception class corresponding to given DLite error code.
+  Returns NULL if `code` is zero.
+ */
+PyObject *dlite_pyembed_exception(DLiteErrors code)
+{
+  const ErrorCorrelation *corr = error_correlations();
+  if (!code) return NULL;
+  while (corr->exc) {
+    if (code == corr->errcode) return corr->exc;
+    corr++;
+  }
+  return PyExc_Exception;
+}
+
+
 /*
   Writes Python error message to `errmsg` (of length `len`) if an
   Python error has occured.
@@ -267,9 +360,14 @@ int dlite_pyembed_err_check(const char *msg, ...)
  */
 int dlite_pyembed_verr_check(const char *msg, va_list ap)
 {
-  /* TODO: can we correlate the return value to Python error type? */
-  if (PyErr_Occurred())
-    return dlite_pyembed_verr(1, msg, ap);
+  PyObject *err;
+  //PyGILState_STATE state = PyGILState_STATE();
+  err = PyErr_Occurred();
+  //PyGILState_Release(state);
+  if (err) {
+    int eval = dlite_pyembed_errcode(err);
+    return dlite_pyembed_verr(eval, msg, ap);
+  }
   return 0;
 }
 

src/pyembed/dlite-pyembed.h

@@ -18,6 +18,11 @@
 #include "utils/plugin.h"
 #include "dlite.h"
 
+/* Remove __attribute__ when we are not compiling with gcc */
+#ifndef __GNUC__
+# define __attribute__(x)
+#endif
+
 
 /**
   Initialises the embedded Python environment.
@@ -35,6 +40,16 @@ int dlite_pyembed_finalise(void);
 */
 const char *dlite_pyembed_classname(PyObject *cls);
 
+/**
+  Return DLite error code given Python exception type.
+ */
+DLiteErrors dlite_pyembed_errcode(PyObject *type);
+
+/**
+  Return Python exception class corresponding to given DLite error code.
+  Returns NULL if `code` is zero.
+ */
+PyObject *dlite_pyembed_exception(DLiteErrors code);
 
 /**
   Writes Python error message to `errmsg` (of length `len`) if an
@@ -56,24 +71,28 @@ int dlite_pyembed_errmsg(char *errmsg, size_t errlen);
 
   Returns `eval`.
  */
-int dlite_pyembed_err(int eval, const char *msg, ...);
+int dlite_pyembed_err(int eval, const char *msg, ...)
+  __attribute__ ((__format__ (__printf__, 2, 3)));
 
 /**
   Like dlite_pyembed_err() but takes a `va_list` as input.
  */
-int dlite_pyembed_verr(int eval, const char *msg, va_list ap);
+int dlite_pyembed_verr(int eval, const char *msg, va_list ap)
+  __attribute__ ((__format__ (__printf__, 2, 0)));
 
 /**
   Checks if an Python error has occured.  Returns zero if no error has
   occured.  Otherwise dlite_pyembed_err() is called and non-zero is
   returned.
  */
-int dlite_pyembed_err_check(const char *msg, ...);
+int dlite_pyembed_err_check(const char *msg, ...)
+  __attribute__ ((__format__ (__printf__, 1, 2)));
 
 /**
   Like dlite_pyembed_err_check() but takes a `va_list` as input.
  */
-int dlite_pyembed_verr_check(const char *msg, va_list ap);
+int dlite_pyembed_verr_check(const char *msg, va_list ap)
+  __attribute__ ((__format__ (__printf__, 1, 0)));
 
 
 /**

src/pyembed/dlite-python-singletons.c

@@ -67,3 +67,18 @@ PyObject *dlite_python_mapping_base(void)
 {
   return dlite_python_mainclass("DLiteMappingBase");
 }
+
+
+/*
+  Returns a singleton Python exception object for the given DLite error code.
+
+  The singleton object is created the first time this function is called
+  with a given `code`.  All following calles with the same `code` will return
+  a reference to the same object.
+
+  Returns NULL if `code` is out of range.
+*/
+//PyObject *dlite_python_error(DLiteErrors code)
+//{
+//
+//}