Add 'X in tuple()' support to gclient conditionals.

This is purely so I can land:
https://chromium-review.googlesource.com/c/chromium/src/+/1625812
instead of:
https://chromium-review.googlesource.com/c/chromium/src/+/1625813

That is, the former is a slightly cleaner version of the latter. However,
it doesn't work w/o this patch.

Bug: 947531
Change-Id: If8e7f8080ba5f40408680b598fed511df89be8bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1626479
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>

gclient_eval.py

@@ -538,9 +538,11 @@ def EvaluateCondition(condition, variables, referenced_variables=None):
   main_node = ast.parse(condition, mode='eval')
   if isinstance(main_node, ast.Expression):
     main_node = main_node.body
-  def _convert(node):
+  def _convert(node, allow_tuple=False):
     if isinstance(node, ast.Str):
       return node.s
+    elif isinstance(node, ast.Tuple) and allow_tuple:
+      return tuple(map(_convert, node.elts))
     elif isinstance(node, ast.Name):
       if node.id in referenced_variables:
         raise ValueError(
@@ -612,12 +614,15 @@ def _convert(node):
                 condition))
 
       left = _convert(node.left)
-      right = _convert(node.comparators[0])
+      right = _convert(
+          node.comparators[0], allow_tuple=isinstance(node.ops[0], ast.In))
 
       if isinstance(node.ops[0], ast.Eq):
         return left == right
       if isinstance(node.ops[0], ast.NotEq):
         return left != right
+      if isinstance(node.ops[0], ast.In):
+        return left in right
 
       raise ValueError(
           'unexpected operator: %s %s (inside %r)' % (

tests/gclient_eval_unittest.py

@@ -265,6 +265,21 @@ def test_string_bool_typo(self):
             '(inside \'false_var_str and true_var\')',
         str(cm.exception))
 
+  def test_tuple_presence(self):
+    self.assertTrue(gclient_eval.EvaluateCondition(
+      'foo in ("bar", "baz")', {'foo': 'bar'}))
+    self.assertFalse(gclient_eval.EvaluateCondition(
+      'foo in ("bar", "baz")', {'foo': 'not_bar'}))
+
+  def test_unsupported_tuple_operation(self):
+    with self.assertRaises(ValueError) as cm:
+      gclient_eval.EvaluateCondition('foo == ("bar", "baz")', {'foo': 'bar'})
+    self.assertIn('unexpected AST node', str(cm.exception))
+
+    with self.assertRaises(ValueError) as cm:
+      gclient_eval.EvaluateCondition('(foo,) == "bar"', {'foo': 'bar'})
+    self.assertIn('unexpected AST node', str(cm.exception))
+
 
 class VarTest(unittest.TestCase):
   def assert_adds_var(self, before, after):