Add a test for attack_filter with melee-only vs ranged-only units

A new test of what happens when a unit with only a ranged weapon fights a
unit with only a melee weapon. This commit is just the test, it depends on
the engine fix in a previous commit.

This only tests the filtering so far. There should probably be another
additional test to check what the combat results are, however that would need
an ability such as the Deep Elves' Stardust that passively affects the amount
of damage taken. It can't be tested with Slows, as that needs the defender to
hit with a weapon first.

data/test/scenarios/wml_tests/ScenarioWML/EventWML/events-test_filter_attack_no_defense.cfg

@@ -0,0 +1,108 @@
+# wmllint: no translatables
+
+#####
+# API(s) being tested: [event][filter_attack]
+##
+# Actions:
+# Remove Alice's melee attack.
+# Give Alice an ability that adds a drain special to all of his weapons.
+# Define events that use filter_attack matching Alice's drain special.
+# Have Alice use a ranged attack against Bob, who only has a melee attack.
+# Have Bob use a melee attack against Alice.
+##
+# Expected end state:
+# An event triggers when Alice attacks during side 1's turn.
+# No event triggers when Bob attacks Alice.
+#####
+{GENERIC_UNIT_TEST event_test_filter_attack_no_defense (
+    [event]
+        name=turn 1
+        [object]
+            silent=yes
+            [effect]
+                apply_to=remove_attacks
+                range=melee
+            [/effect]
+            [effect]
+                apply_to=new_ability
+                [abilities]
+                    [drains]
+                        id=test_ability_drain
+                    [/drains]
+                [/abilities]
+            [/effect]
+            [filter]
+                id=alice
+            [/filter]
+        [/object]
+        [modify_unit]
+            [filter]
+            [/filter]
+            # Make sure they don't die during the attacks
+            [status]
+                invulnerable=yes
+            [/status]
+        [/modify_unit]
+        [do_command]
+            [move]
+                x=7,13
+                y=3,4
+            [/move]
+            [attack]
+                [source]
+                    x,y=13,4
+                [/source]
+                [destination]
+                    x,y=13,3
+                [/destination]
+            [/attack]
+        [/do_command]
+        [end_turn][/end_turn]
+    [/event]
+
+    [event]
+        name=side 2 turn
+        [do_command]
+            [attack]
+                [source]
+                    x,y=13,3
+                [/source]
+                [destination]
+                    x,y=13,4
+                [/destination]
+            [/attack]
+        [/do_command]
+        [end_turn][/end_turn]
+    [/event]
+
+    # Event when Alice attacks
+    [event]
+        name=attack
+        first_time_only=no
+        [filter_attack]
+            special_id_active=test_ability_drain
+        [/filter_attack]
+        {ASSERT ({VARIABLE_CONDITIONAL side_number equals 1})}
+        {VARIABLE_OP triggers_on_attack add 1}
+    [/event]
+
+    # As Alice only has a ranged attack, this shouldn't fire in response to Bob's melee attack.
+    #
+    # Inside the engine, [second]name=none has been passed to the filter code, and a placeholder
+    # [attack]damage,num_attacks=0,0 generated. Alice's ability gives the drain ability to all of
+    # his attacks, this checks that the drain ability isn't given to the dummy one when filtering.
+    [event]
+        name=attack
+        first_time_only=no
+        [filter_second_attack]
+            special_id_active=test_ability_drain
+        [/filter_second_attack]
+        {FAIL}
+    [/event]
+
+    [event]
+        name=turn 2
+        {ASSERT ({VARIABLE_CONDITIONAL triggers_on_attack equals 1})}
+        {SUCCEED}
+    [/event]
+)}

wml_test_schedule

@@ -144,6 +144,7 @@
 0 test_ability_id_active
 0 test_ability_id_not_active
 0 event_test_filter_attack
+0 event_test_filter_attack_no_defense
 0 event_test_filter_attack_specials
 0 event_test_filter_attack_opponent_weapon_condition
 0 event_test_filter_wfl