[3.8] bpo-40179: Fix translation of #elif in Argument Clinic (GH-19364) (GH-19583)

Co-authored-by: Ammar Askar <ammar@ammaraskar.com>
(cherry picked from commit 12446e6a605f066d837d3a595d0a73e4f3b43b65)

1 files changed, 16 insertions, 21 deletions

diff --git a/Tools/clinic/cpp.py b/Tools/clinic/cpp.py
index e099590..77f5f96 100644
--- a/Tools/clinic/cpp.py
+++ b/Tools/clinic/cpp.py
@@ -141,23 +141,15 @@ class Monitor:
         token = fields[0].lower()
         condition = ' '.join(fields[1:]).strip()
 
-        if_tokens = {'if', 'ifdef', 'ifndef'}
-        all_tokens = if_tokens | {'elif', 'else', 'endif'}
-
-        if token not in all_tokens:
-            return
-
-        # cheat a little here, to reuse the implementation of if
-        if token == 'elif':
-            pop_stack()
-            token = 'if'
-
-        if token in if_tokens:
+        if token in {'if', 'ifdef', 'ifndef', 'elif'}:
             if not condition:
                 self.fail("Invalid format for #" + token + " line: no argument!")
-            if token == 'if':
+            if token in {'if', 'elif'}:
                 if not self.is_a_simple_defined(condition):
                     condition = "(" + condition + ")"
+                if token == 'elif':
+                    previous_token, previous_condition = pop_stack()
+                    self.stack.append((previous_token, negate(previous_condition)))
             else:
                 fields = condition.split()
                 if len(fields) != 1:
@@ -166,18 +158,21 @@ class Monitor:
                 condition = 'defined(' + symbol + ')'
                 if token == 'ifndef':
                     condition = '!' + condition
+                token = 'if'
 
-            self.stack.append(("if", condition))
-            if self.verbose:
-                print(self.status())
-            return
+            self.stack.append((token, condition))
 
-        previous_token, previous_condition = pop_stack()
+        elif token == 'else':
+            previous_token, previous_condition = pop_stack()
+            self.stack.append((previous_token, negate(previous_condition)))
 
-        if token == 'else':
-            self.stack.append(('else', negate(previous_condition)))
         elif token == 'endif':
-            pass
+            while pop_stack()[0] != 'if':
+                pass
+
+        else:
+            return
+
         if self.verbose:
             print(self.status())