Simplify redundant 'is (not) None' tests

Menu node pointers and .choice in particular is always either an object
or None. Prompts are always either a (text, cond) tuple or None. Some
other things could (though unlikely) be empty strings, and some things
use symbolic constants that might be 0, so keep the None tests there.

Cleaner, especially for menu nodes.

Also remove redundant 'node2.dep is None' test. Expressions are never
None.

Also fix node.prompt == "" comparison in _flatten(). Should be
node.prompt[0] == "". Not sure why the C implementation checks for an
existing but empty prompt to begin with. It's just cosmetic menu stuff
at least.

1 files changed, 40 insertions, 44 deletions

diff --git a/kconfiglib.py b/kconfiglib.py
index 9a6292e..c89e439 100644
--- a/kconfiglib.py
+++ b/kconfiglib.py
@@ -598,7 +598,7 @@ class Kconfig(object):
         """
         See the class documentation.
         """
-        if self.defconfig_list is None:
+        if not self.defconfig_list:
             return None
 
         for filename, cond in self.defconfig_list.defaults:
@@ -692,7 +692,7 @@ class Kconfig(object):
                         # We represent tristate values as 0, 1, 2
                         val = STR_TO_TRI[val[0]]
 
-                        if sym.choice is not None and val:
+                        if sym.choice and val:
                             # During .config loading, we infer the mode of the
                             # choice from the kind of values that are assigned
                             # to the choice symbols
@@ -1437,7 +1437,7 @@ class Kconfig(object):
                 else:
                     # Named choice
                     choice = self.named_choices.get(name)
-                    if choice is None:
+                    if not choice:
                         choice = Choice()
                         self._choices.append(choice)
                         choice.name = name
@@ -1620,7 +1620,7 @@ class Kconfig(object):
                              self.y))
 
                 elif self._check_token(_T_DEFCONFIG_LIST):
-                    if self.defconfig_list is None:
+                    if not self.defconfig_list:
                         self.defconfig_list = node.item
                     else:
                         self._warn("'option defconfig_list' set on multiple "
@@ -1698,7 +1698,7 @@ class Kconfig(object):
                     self._make_or(node.item.direct_dep, node.dep)
 
             # Set the prompt, with dependencies propagated
-            if prompt is not None:
+            if prompt:
                 node.prompt = (prompt[0],
                                self._make_and(self._make_and(prompt[1],
                                                              node.dep),
@@ -1849,7 +1849,7 @@ class Kconfig(object):
 
             # The prompt conditions
             for node in sym.nodes:
-                if node.prompt is not None:
+                if node.prompt:
                     _make_depend_on(sym, node.prompt[1])
 
             # The default values and their conditions
@@ -1884,7 +1884,7 @@ class Kconfig(object):
 
             # The prompt conditions
             for node in choice.nodes:
-                if node.prompt is not None:
+                if node.prompt:
                     _make_depend_on(choice, node.prompt[1])
 
             # The default symbol conditions
@@ -1930,7 +1930,7 @@ class Kconfig(object):
             sym._already_written = False
 
         node = self.top_node.list
-        if node is None:
+        if not node:
             # Empty configuration
             return []
 
@@ -1943,7 +1943,7 @@ class Kconfig(object):
                 sym = node.item
                 if not sym._already_written:
                     config_string = sym.config_string
-                    if config_string is not None:
+                    if config_string:
                         add_fn(config_string)
                     sym._already_written = True
 
@@ -1955,14 +1955,14 @@ class Kconfig(object):
 
             # Iterative tree walk using parent pointers
 
-            if node.list is not None:
+            if node.list:
                 node = node.list
-            elif node.next is not None:
+            elif node.next:
                 node = node.next
             else:
-                while node.parent is not None:
+                while node.parent:
                     node = node.parent
-                    if node.next is not None:
+                    if node.next:
                         node = node.next
                         break
                 else:
@@ -1986,7 +1986,7 @@ class Kconfig(object):
             sym = self.syms.get(sym_ref_match.group(1))
 
             s = s[:sym_ref_match.start()] + \
-                (sym.str_value if sym is not None else "") + \
+                (sym.str_value if sym else "") + \
                 s[sym_ref_match.end():]
 
     def _parse_error(self, msg):
@@ -2250,7 +2250,7 @@ class Symbol(object):
         See the class documentation.
         """
         if self.orig_type == TRISTATE and \
-           ((self.choice is not None and self.choice.tri_value == 2) or
+           ((self.choice and self.choice.tri_value == 2) or
             not self.kconfig.modules.tri_value):
             return BOOL
 
@@ -2552,7 +2552,7 @@ class Symbol(object):
 
             return False
 
-        if self.choice is not None and value == 2:
+        if self.choice and value == 2:
             # Remember this as a choice selection only. Makes switching back
             # and forth between choice modes work as expected, and makes the
             # check for whether the user value is the same as before above
@@ -2591,7 +2591,7 @@ class Symbol(object):
         fields.append(TYPE_TO_STR[self.type])
 
         for node in self.nodes:
-            if node.prompt is not None:
+            if node.prompt:
                 fields.append('"{}"'.format(node.prompt[0]))
 
         # Only add quotes for non-bool/tristate symbols
@@ -2612,7 +2612,7 @@ class Symbol(object):
 
             fields.append("visibility " + TRI_TO_STR[self.visibility])
 
-            if self.choice is not None:
+            if self.choice:
                 fields.append("choice symbol")
 
             if self.is_allnoconfig_y:
@@ -2764,7 +2764,7 @@ class Symbol(object):
         normal and expected, so the warning can be disabled.
         """
         for node in self.nodes:
-            if node.prompt is not None:
+            if node.prompt:
                 return True
 
         if self.kconfig._warn_no_prompt:
@@ -3039,8 +3039,7 @@ class Choice(object):
             return None
 
         # User choice available?
-        if self.user_selection is not None and \
-           self.user_selection.visibility == 2:
+        if self.user_selection and self.user_selection.visibility == 2:
             self._cached_selection = self.user_selection
             return self.user_selection
 
@@ -3103,7 +3102,7 @@ class Choice(object):
         Resets the user value (mode) and user selection of the Choice, as if
         the user had never touched the mode or any of the choice symbols.
         """
-        if self.user_value is not None or self.user_selection is not None:
+        if self.user_value is not None or self.user_selection:
             self.user_value = self.user_selection = None
             self._rec_invalidate()
 
@@ -3119,7 +3118,7 @@ class Choice(object):
         fields.append(TYPE_TO_STR[self.type])
 
         for node in self.nodes:
-            if node.prompt is not None:
+            if node.prompt:
                 fields.append('"{}"'.format(node.prompt[0]))
 
         fields.append("mode " + self.str_value)
@@ -3127,10 +3126,10 @@ class Choice(object):
         if self.user_value is not None:
             fields.append('user mode {}'.format(TRI_TO_STR[self.user_value]))
 
-        if self.selection is not None:
+        if self.selection:
             fields.append("{} selected".format(self.selection.name))
 
-        if self.user_selection is not None:
+        if self.user_selection:
             user_sel_str = "{} selected by user" \
                            .format(self.user_selection.name)
 
@@ -3353,7 +3352,7 @@ class MenuNode(object):
             raise InternalError("unable to determine type in "
                                 "MenuNode.__repr__()")
 
-        if self.prompt is not None:
+        if self.prompt:
             fields.append('prompt "{}" (visibility {})'
                           .format(self.prompt[0],
                                   TRI_TO_STR[expr_value(self.prompt[1])]))
@@ -3370,10 +3369,10 @@ class MenuNode(object):
         if isinstance(self.item, (Symbol, Choice)) and self.help is not None:
             fields.append("has help")
 
-        if self.list is not None:
+        if self.list:
             fields.append("has child")
 
-        if self.next is not None:
+        if self.next:
             fields.append("has next")
 
         fields.append("{}:{}".format(self.filename, self.linenr))
@@ -3562,7 +3561,7 @@ def _get_visibility(sc):
         if node.prompt:
             vis = max(vis, expr_value(node.prompt[1]))
 
-    if isinstance(sc, Symbol) and sc.choice is not None:
+    if isinstance(sc, Symbol) and sc.choice:
         if sc.choice.orig_type == TRISTATE and sc.orig_type != TRISTATE and \
            sc.choice.tri_value != 2:
             # Non-tristate choice symbols are only visible in y mode
@@ -3698,7 +3697,7 @@ def _sym_choice_str(sc):
         if node is sc.nodes[0] and sc.orig_type != UNKNOWN:
             indent_add(TYPE_TO_STR[sc.orig_type])
 
-        if node.prompt is not None:
+        if node.prompt:
             prompt, cond = node.prompt
             prompt_str = 'prompt "{}"'.format(escape(prompt))
             if cond is not sc.kconfig.y:
@@ -3803,8 +3802,7 @@ def _has_auto_menu_dep(node1, node2):
         return _expr_depends_on(node2.prompt[1], node1.item)
 
     # If we have no prompt, use the menu node dependencies instead
-    return node2.dep is not None and \
-           _expr_depends_on(node2.dep, node1.item)
+    return _expr_depends_on(node2.dep, node1.item)
 
 def _check_auto_menu(node):
     """
@@ -3813,8 +3811,7 @@ def _check_auto_menu(node):
     found. The recursive call to _finalize_tree() makes this work recursively.
     """
     cur = node
-    while cur.next is not None and \
-          _has_auto_menu_dep(node, cur.next):
+    while cur.next and _has_auto_menu_dep(node, cur.next):
         _finalize_tree(cur.next)
         cur = cur.next
         cur.parent = node
@@ -3831,14 +3828,13 @@ def _flatten(node):
     appear after them instead. This gives a clean menu structure with no
     unexpected "jumps" in the indentation.
     """
-    while node is not None:
-        if node.list is not None and \
-           (node.prompt is None or node.prompt == ""):
+    while node:
+        if node.list and (not node.prompt or node.prompt[0] == ""):
 
             last_node = node.list
             while 1:
                 last_node.parent = node.parent
-                if last_node.next is None:
+                if not last_node.next:
                     break
                 last_node = last_node.next
 
@@ -3856,12 +3852,12 @@ def _remove_ifs(node):
     makes it nicer to work with.
     """
     first = node.list
-    while first is not None and first.item is None:
+    while first and first.item is None:
         first = first.next
 
     cur = first
-    while cur is not None:
-        if cur.next is not None and cur.next.item is None:
+    while cur:
+        if cur.next and cur.next.item is None:
             cur.next = cur.next.next
         cur = cur.next
 
@@ -3905,10 +3901,10 @@ def _finalize_tree(node):
     # The ordering here gets a bit tricky. It's important to do things in this
     # order to have everything work out correctly.
 
-    if node.list is not None:
+    if node.list:
         # The menu node has children. Finalize them.
         cur = node.list
-        while cur is not None:
+        while cur:
             _finalize_tree(cur)
             # Note: _finalize_tree() might have changed cur.next. This is
             # expected, so that we jump over e.g. implicitly created submenus.
@@ -3919,7 +3915,7 @@ def _finalize_tree(node):
         # menu rooted at it (due to menu nodes after it depending on it).
         _check_auto_menu(node)
 
-    if node.list is not None:
+    if node.list:
         # We have a node with finalized children. Do final steps to finalize
         # this node.
         _flatten(node.list)