Test disabler in foreach loops

The is_disabler() check in evaluate_foreach() was useless because we
already checked that items is a list.

mesonbuild/interpreterbase.py

@@ -682,8 +682,6 @@ The result of this is undefined and will become a hard error in a future Meson r
             if len(node.varnames) != 1:
                 raise InvalidArguments('Foreach on array does not unpack')
             varname = node.varnames[0].value
-            if is_disabler(items):
-                return items
             for item in items:
                 self.set_variable(varname, item)
                 try:
@@ -695,8 +693,6 @@ The result of this is undefined and will become a hard error in a future Meson r
         elif isinstance(items, dict):
             if len(node.varnames) != 2:
                 raise InvalidArguments('Foreach on dict unpacks key and value')
-            if is_disabler(items):
-                return items
             for key, value in items.items():
                 self.set_variable(node.varnames[0].value, key)
                 self.set_variable(node.varnames[1].value, value)

test cases/common/163 disabler/meson.build

@@ -98,3 +98,25 @@ else
   if_is_disabled = false
 endif
 assert(if_is_disabled, 'Disabler in "if a==b" must skip both blocks')
+
+loops = 0
+disablers = 0
+foreach i : [true, disabler(), true]
+  loops += 1
+  if is_disabler(i)
+    disablers += 1
+  endif
+endforeach
+assert(loops == 3, 'Disabler in foreach array')
+assert(disablers == 1, 'Disabler in foreach array')
+
+loops = 0
+disablers = 0
+foreach k, i : {'a': true, 'b': disabler(), 'c': true}
+  loops += 1
+  if is_disabler(i)
+    disablers += 1
+  endif
+endforeach
+assert(loops == 3, 'Disabler in foreach dict')
+assert(disablers == 1, 'Disabler in foreach dict')