Fix: random_switch with triggers has side-effects, and thus must not …

…be optimised away.

nml/ast/switch.py

@@ -359,6 +359,9 @@ def pre_process(self):
     def optimise(self):
         if self.optimised:
             return True
+        if self.triggers.value != 0:
+            # Triggers have side-effects, and can't be skipped.
+            return False
         if len(self.choices) == 1:
             generic.print_warning("Block '{}' returns a constant, optimising.".format(self.name.value), self.pos)
             self.optimised = self.choices[0].result.value

regression/037_optimised_trigger.nml

@@ -0,0 +1,22 @@
+grf {
+    grfid: "NML\37";
+    name: string(STR_REGRESSION_NAME);
+    desc: string(STR_REGRESSION_DESC);
+    version: 0;
+    min_compatible_version: 0;
+}
+
+random_switch(FEAT_TRAINS, SELF, unconditional_switch) {
+    8: return 5;
+}
+
+random_switch(FEAT_TRAINS, SELF, trigger_only, bitmask(TRIGGER_VEHICLE_NEW_LOAD)) {
+    8: return 7;
+}
+
+item(FEAT_TRAINS, colored_train, 100) {
+    graphics {
+        colour_mapping: unconditional_switch;
+        default: trigger_only;
+    }
+}

regression/expected/037_optimised_trigger.nfo

@@ -0,0 +1,35 @@
+// Automatically generated by GRFCODEC. Do not modify!
+// (Info version 32)
+// Escapes: 2+ 2- 2< 2> 2u< 2u> 2/ 2% 2u/ 2u% 2* 2& 2| 2^ 2sto = 2s 2rst = 2r 2psto 2ror = 2rot 2cmp 2ucmp 2<< 2u>> 2>>
+// Escapes: 71 70 7= 7! 7< 7> 7G 7g 7gG 7GG 7gg 7c 7C
+// Escapes: D= = DR D+ = DF D- = DC Du* = DM D* = DnF Du<< = DnC D<< = DO D& D| Du/ D/ Du% D%
+// Format: spritenum imagefile depth xpos ypos xsize ysize xrel yrel zoom flags
+
+0 * 4 \d6
+
+1 * 54 14 "C" "INFO"
+"B" "VRSN" \w4 \dx00000000
+"B" "MINV" \w4 \dx00000000
+"B" "NPAR" \w1 00
+"B" "PALS" \w1 "A"
+"B" "BLTR" \w1 "8"
+00
+00
+2 * 52 08 08 "NML\37" "NML regression test" 00 "A test newgrf testing NML" 00
+// Name: trigger_only
+3 * 23 02 00 FF 80 01 \b0 08
+\wx8007 \wx8007 \wx8007 \wx8007 \wx8007 \wx8007 \wx8007 \wx8007 // (8/8) -> (8/8): return 7;
+
+4 * 9 00 00 \b1 01 FF \wx0064
+1E 40
+
+// Name: @action3_0
+5 * 23 02 00 FF 89
+0C 00 \dx0000FFFF
+\b1
+\wx8005 \dx0000002D \dx0000002D 	// return 5;
+\wx00FF // trigger_only;
+
+6 * 9 03 00 01 FF \wx0064 \b0
+\wx00FF 	// @action3_0;
+