Fix removal of multiple consecutive 'if' nodes

Despite 'if' nodes being flattened before 'if' removal, consecutive 'if'
nodes can still show up for code like the following:

  ...

  if X
  endif

  if X
  endif

  ...

_remove_ifs() failed to remove the second 'if' node, leading to a crash
e.g. when turning on show-all mode in the menuconfig in a menu with such
code (due to the unexpected 'if' node).

Stuff like the above could potentially result from 'osource's with no
matches, though I just spotted the error while looking over the code.

Fix the 'if' removal logic to properly handle consecutive 'if' nodes.

3 files changed, 129 insertions, 11 deletions

diff --git a/kconfiglib.py b/kconfiglib.py
index eae271e..96e6b52 100644
--- a/kconfiglib.py
+++ b/kconfiglib.py
@@ -5822,17 +5822,17 @@ def _remove_ifs(node):
     node.list = cur
 
     while cur:
-        if cur.next and not cur.next.item:
-            # Equivalent to
-            #
-            #   tmp = cur.next.next
-            #   cur.next = tmp
-            #   cur = tmp
-            #
-            # due to tricky Python semantics. The order matters.
-            cur.next = cur = cur.next.next
-        else:
-            cur = cur.next
+        next = cur.next
+        while next and not next.item:
+            next = next.next
+
+        # Equivalent to
+        #
+        #   cur.next = next
+        #   cur = next
+        #
+        # due to tricky Python semantics. The order matters.
+        cur.next = cur = next
 
 def _finalize_choice(node):
     # Finalizes a choice, marking each symbol whose menu node has the choice as
diff --git a/tests/Kifremoval b/tests/Kifremoval
new file mode 100644
index 0000000..f94472c
--- /dev/null
+++ b/tests/Kifremoval
@@ -0,0 +1,99 @@
+# Test some tricky cases that give consecutive 'if' nodes even after
+# flattening. Simple cases are exercised a ton elsewhere.
+
+if X
+endif
+if X
+endif
+
+config A
+
+if X
+endif
+if X
+endif
+
+config B
+
+if X
+endif
+if X
+endif
+if X
+endif
+
+config C
+
+if X
+  if X
+    if X
+    endif
+    if X
+    endif
+  endif
+  if X
+    if X
+    endif
+    if X
+    endif
+  endif
+  config D
+endif
+if X
+endif
+
+menu "E"
+  if X
+    if X
+    endif
+  endif
+  if X
+    if X
+    endif
+  endif
+endmenu
+
+menu "F"
+  if X
+  endif
+  if X
+  endif
+  if X
+    if X
+    endif
+    if X
+    endif
+    menu "G"
+    endmenu
+  endif
+endmenu
+
+choice H
+  if X
+    if X
+    endif
+  endif
+  if X
+    if X
+    endif
+  endif
+endchoice
+
+choice I
+  if X
+  endif
+  if X
+  endif
+  if X
+    if X
+    endif
+    if X
+    endif
+    config J
+  endif
+endchoice
+
+if X
+endif
+if X
+endif
diff --git a/testsuite.py b/testsuite.py
index cca5dad..6f05b6a 100644
--- a/testsuite.py
+++ b/testsuite.py
@@ -2212,6 +2212,25 @@ CONFIG_G=-1
     verify_is_normal_choice_symbol("WS9")
 
 
+    print("Testing 'if' node removal")
+
+    c = Kconfig("Kconfiglib/tests/Kifremoval", warn=False)
+
+    nodes = [node for node in c.node_iter()]
+    verify_equal(nodes[0].item.name, "A")
+    verify_equal(nodes[1].item.name, "B")
+    verify_equal(nodes[2].item.name, "C")
+    verify_equal(nodes[3].item.name, "D")
+    verify_equal(nodes[4].prompt[0], "E")
+    verify_equal(nodes[5].prompt[0], "F")
+    verify_equal(nodes[6].prompt[0], "G")
+    verify_equal(nodes[7].item.name, "H")
+    verify_equal(nodes[8].item.name, "I")
+    verify_equal(nodes[9].item.name, "J")
+    verify(len(nodes) == 10,
+           "Wrong number of nodes after 'if' removal")
+
+
     print("Testing multi.def. property copying")
 
     c = Kconfig("Kconfiglib/tests/Kdepcopy", warn=False)