fix: show CQL help in cqlsh in web browser

patch by Robert Stupp; reviewed by Paulo Motta for CASSANDRA-7225

bin/cqlsh.py

@@ -71,6 +71,7 @@ except ImportError:
 CQL_LIB_PREFIX = 'cassandra-driver-internal-only-'
 
 CASSANDRA_PATH = os.path.join(os.path.dirname(os.path.realpath(__file__)), '..')
+CASSANDRA_CQL_HTML_FALLBACK = 'https://cassandra.apache.org/doc/cql3/CQL-2.2.html'
 
 if os.path.exists(CASSANDRA_PATH + '/doc/cql3/CQL.html'):
     # default location of local CQL.html
@@ -80,7 +81,7 @@ elif os.path.exists('/usr/share/doc/cassandra/CQL.html'):
     CASSANDRA_CQL_HTML = 'file:///usr/share/doc/cassandra/CQL.html'
 else:
     # fallback to online version
-    CASSANDRA_CQL_HTML = 'https://cassandra.apache.org/doc/cql3/CQL-2.2.html'
+    CASSANDRA_CQL_HTML = CASSANDRA_CQL_HTML_FALLBACK
 
 # On Linux, the Python webbrowser module uses the 'xdg-open' executable
 # to open a file/URL. But that only works, if the current session has been
@@ -92,7 +93,9 @@ else:
 # >>> webbrowser._tryorder
 # >>> webbrowser._browser
 #
-if webbrowser._tryorder[0] == 'xdg-open' and os.environ.get('XDG_DATA_DIRS', '') == '':
+if len(webbrowser._tryorder) == 0:
+    CASSANDRA_CQL_HTML = CASSANDRA_CQL_HTML_FALLBACK
+elif webbrowser._tryorder[0] == 'xdg-open' and os.environ.get('XDG_DATA_DIRS', '') == '':
     # only on Linux (some OS with xdg-open)
     webbrowser._tryorder.remove('xdg-open')
     webbrowser._tryorder.append('xdg-open')
@@ -2213,7 +2216,9 @@ class Shell(cmd.Cmd):
                 urlpart = cqldocs.get_help_topic(t)
                 if urlpart is not None:
                     url = "%s#%s" % (CASSANDRA_CQL_HTML, urlpart)
-                    if self.browser is not None:
+                    if len(webbrowser._tryorder) == 0:
+                        self.printerr("*** No browser to display CQL help. URL for help topic %s : %s" % (t, url))
+                    elif self.browser is not None:
                         webbrowser.get(self.browser).open_new_tab(url)
                     else:
                         webbrowser.open_new_tab(url)

pylib/cqlshlib/helptopics.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from .cql3handling import simple_cql_types
-
 
 class CQL3HelpTopics(object):
 
@@ -73,8 +71,10 @@ class CQL3HelpTopics(object):
 
     def help_json(self):
         return 'json'
+
     def help_select_json(self):
         return 'selectJson'
+
     def help_insert_json(self):
         return 'insertJson'
 
@@ -85,21 +85,27 @@ class CQL3HelpTopics(object):
 
     def help_create_keyspace(self):
         return 'createKeyspaceStmt'
+
     def help_alter_keyspace(self):
         return 'alterKeyspaceStmt'
+
     def help_drop_keyspace(self):
         return 'dropKeyspaceStmt'
 
     def help_create_table(self):
         return 'createTableStmt'
     help_create_columnfamily = help_create_table
+
     def help_alter_table(self):
         return 'alterTableStmt'
+
     def help_drop_table(self):
         return 'dropTableStmt'
     help_drop_columnfamily = help_drop_table
+
     def help_create_index(self):
         return 'createIndexStmt'
+
     def help_drop_index(self):
         return 'dropIndexStmt'
 
@@ -108,27 +114,34 @@ class CQL3HelpTopics(object):
 
     def help_create_type(self):
         return 'createTypeStmt'
+
     def help_alter_type(self):
         return 'alterTypeStmt'
+
     def help_drop_type(self):
         return 'dropTypeStmt'
 
     def help_create_function(self):
         return 'createFunctionStmt'
+
     def help_drop_function(self):
         return 'dropFunctionStmt'
+
     def help_functions(self):
         return 'functions'
 
     def help_create_aggregate(self):
         return 'createAggregateStmt'
+
     def help_drop_aggregate(self):
         return 'dropAggregateStmt'
+
     def help_aggregates(self):
         return 'aggregates'
 
     def help_create_trigger(self):
         return 'createTriggerStmt'
+
     def help_drop_trigger(self):
         return 'dropTriggerStmt'
 
@@ -137,19 +150,24 @@ class CQL3HelpTopics(object):
 
     def help_create_user(self):
         return 'createUserStmt'
+
     def help_alter_user(self):
         return 'alterUserStmt'
+
     def help_drop_user(self):
         return 'dropUserStmt'
+
     def help_list_users(self):
         return 'listUsersStmt'
 
     def help_permissions(self):
         return 'permissions'
+
     def help_list_permissions(self):
         return 'listPermissionsStmt'
 
     def help_grant(self):
         return 'grantRoleStmt'
+
     def help_revoke(self):
         return 'revokeRoleStmt'