Fixed segfault in iteration over storage plugin names

Also changed plugin help to be a class method.

bindings/python/dlite-storage-python.i

@@ -8,7 +8,7 @@
       # Override default __init__()
       def __init__(self, driver_or_url, location=None, options=None):
           loc = str(location) if location else None
-          _dlite.Instance_swiginit(self, _dlite.new_Storage(
+          _dlite.Storage_swiginit(self, _dlite.new_Storage(
               driver_or_url=driver_or_url, location=loc, options=options))
 
       def __enter__(self):
@@ -41,10 +41,25 @@
       )
 
       @classmethod
-      def create_from_url(cls, url):
+      def from_url(cls, url):
           """Create a new storage from `url`."""
           return cls(url)
 
+      @classmethod
+      def load_plugins(cls):
+          """Load all storage plugins."""
+          _dlite._load_all_storage_plugins()
+
+      @classmethod
+      def unload_plugin(cls, name):
+          """Unload storage plugin with this name."""
+          _dlite._unload_storage_plugin(str(name))
+
+      @classmethod
+      def plugin_help(cls, name):
+          """Return documentation of storage plogin with this name."""
+          return _dlite._storage_plugin_help(name)
+
       def instances(self, pattern=None):
           """Returns an iterator over all instances in storage whos
           metadata URI matches `pattern`."""
@@ -64,6 +79,7 @@
 
       driver = property(get_driver,
                         doc='Name of driver associated with this storage')
+
   %}
 }
 
@@ -77,12 +93,24 @@
   %}
 }
 
-
 %extend StoragePluginIter {
   %pythoncode %{
+      # Override default __init__()
+      def __init__(self):
+          """Iterates over loaded storage plugins."""
+          _dlite.StoragePluginIter_swiginit(
+              self, _dlite.new_StoragePluginIter())
+          # Keep a reference to self, such that it is not garbage-collected
+          # before end of iterations
+          if not hasattr(_dlite, "_storage_plugin_iters"):
+              _dlite._storage_plugin_iters = {}
+          _dlite._storage_plugin_iters[id(self.iter)] = self
+
       def __next__(self):
           name = self.next()
           if not name:
+              # Delete reference to iterator object stored away in __init__()
+              del _dlite._storage_plugin_iters[id(self.this)]
               raise StopIteration()
           return name
   %}

bindings/python/dlite-storage.i

@@ -2,8 +2,17 @@
 
 %{
 #include "dlite.h"
+#include "dlite-errors.h"
 #include "dlite-storage.h"
 #include "dlite-storage-plugins.h"
+
+char *_storage_plugin_help(const char *name) {
+  const DLiteStoragePlugin *api = dlite_storage_plugin_get(name);
+  if (api->help) return api->help(api);
+  return dlite_err(dliteUnsupportedError,
+                   "\"%s\" storage does not support help", name), NULL;
+}
+
 %}
 
 
@@ -68,8 +77,8 @@ enum _DLiteIDFlag {
 %feature("docstring", "\
 Represents a data storage.
 
-Parameters
-----------
+Arguments
+---------
 driver_or_url : string
     Name of driver used to connect to the storage or, if `location` is not
     given, the URL to the storage:
@@ -195,9 +204,9 @@ Iterates over loaded storage plugins.
     DLiteStoragePluginIter *iter;
   };
 %}
-%feature("docstring", "") new_StoragePluginIter;
 %extend StoragePluginIter {
   StoragePluginIter(void) {
+    //dlite_storage_plugin_load_all();
     DLiteStoragePluginIter *iter = dlite_storage_plugin_iter_create();
     return (struct StoragePluginIter *)iter;
   }
@@ -218,9 +227,14 @@ Iterates over loaded storage plugins.
 }
 
 
-%rename(storage_unload) dlite_storage_plugin_unload;
+%rename(_load_all_storage_plugins) dlite_storage_plugin_load_all;
+int dlite_storage_plugin_load_all();
+
+%rename(_unload_storage_plugin) dlite_storage_plugin_unload;
 int dlite_storage_plugin_unload(const char *name);
 
+char *_storage_plugin_help(const char *name);
+
 
 /* -----------------------------------
  * Target language-spesific extensions

bindings/python/tests/CMakeLists.txt

@@ -9,6 +9,7 @@ set(tests
   test_misc
   test_python_storage
   test_storage
+  test_storage_plugins
   test_paths
   test_utils
   test_global_dlite_state

bindings/python/tests/test_storage_plugins.py

@@ -0,0 +1,25 @@
+import dlite
+
+
+# Initially no storage plugins are loaded
+assert list(dlite.StoragePluginIter()) == []
+
+# Storage plugins can be loaded
+dlite.Storage.load_plugins()
+
+# Now plugins are loaded
+plugins = set(dlite.StoragePluginIter())
+assert plugins
+assert "json" in plugins
+
+# Plugins can be iterated over
+print("Storage plugins")
+plugins2 = set()
+for name in dlite.StoragePluginIter():
+    print("  -", name)
+    plugins2.add(name)
+assert plugins2 == plugins
+
+# Unload json plugin
+dlite.Storage.unload_plugin("json")
+assert "json" not in set(dlite.StoragePluginIter())

src/dlite-storage-plugins.h

@@ -272,7 +272,7 @@ typedef int (*Flush)(DLiteStorage *s);
   Returns a malloc'ed string with plugin documentation or NULL on error.
   Optional.
  */
-typedef char *(*Help)(DLiteStorage *s);
+typedef char *(*Help)(const DLiteStoragePlugin *api);
 
 /** @} */
 

src/dlite-storage.c

@@ -261,7 +261,7 @@ int dlite_storage_delete(DLiteStorage *s, const char *id)
  */
 char *dlite_storage_help(DLiteStorage *s)
 {
-  if (s->api->help) return s->api->help(s);
+  if (s->api->help) return s->api->help(s->api);
   return err(dliteUnsupportedError, "storage does not support help: %s",
              s->api->name), NULL;
 }

src/utils/plugin.c

@@ -80,14 +80,6 @@ PluginInfo *plugin_info_create(const char *kind, const char *symbol,
   map_init(&info->pluginpaths);
   map_init(&info->apis);
 
-  printf("\n");
-  const char *key;
-  map_iter_t iter = map_iter(&info->apis);
-  printf("*** iter:\n");
-  while ((key = map_next(&info->apis, &iter)))
-    printf("*** key='%s'\n", key);
-  printf("*** iterdone:\n");
-
   return info;
 }
 
@@ -422,7 +414,6 @@ char **plugin_names(const PluginInfo *info)
 */
 void plugin_api_iter_init(PluginIter *iter, const PluginInfo *info)
 {
-  printf("*** init iter...\n");
   memset(iter, 0, sizeof(PluginIter));
   iter->info = info;
   iter->miter = map_iter(&info->apis);
@@ -440,7 +431,6 @@ const PluginAPI *plugin_api_iter_next(PluginIter *iter)
   PluginAPI **p, *api=NULL;
   PluginInfo *info = (PluginInfo *)iter->info;
   const char *name = map_next(&info->apis, &iter->miter);
-  printf("  -- '%s'\n", name);
   if (!name) return NULL;
   if (!(p = map_get(&info->apis, name)) || !(api = *p))
     fatal(1, "failed to get api: %s", name);

storages/python/dlite-plugins-python.c

@@ -164,17 +164,17 @@ int flusher(DLiteStorage *s)
   It combines the class documentation with the documentation of the open()
   method.
  */
-char *helper(DLiteStorage *s)
+char *helper(const DLiteStoragePlugin *api)
 {
   PyObject *v=NULL, *pyclassdoc=NULL, *open=NULL, *pyopendoc=NULL;
-  PyObject *class = (PyObject *)s->api->data;
+  PyObject *class = (PyObject *)api->data;
   const char *classname, *classdoc=NULL, *opendoc=NULL;
   char *doc=NULL;
   Py_ssize_t n=0, clen=0, olen=0, i, newlines=0;
 
   dlite_errclr();
   if (!(classname = dlite_pyembed_classname(class)))
-    dlite_warnx("cannot get class name for storage plugin '%s'", s->api->name);
+    dlite_warnx("cannot get class name for storage plugin '%s'", api->name);
 
   if (PyObject_HasAttrString(class, "__doc__")) {
     if (!(pyclassdoc = PyObject_GetAttrString(class, "__doc__")))