Adds CI checks forbidding certain kinds of world loops (#24454)

* Updates checkgrep to report unnecessary loops

* improved message

* global lists are better too

* much better

* Apply suggestions from code review

Co-authored-by: GDN <96800819+GDNgit@users.noreply.github.com>

* update to modern check_grep format

---------

Co-authored-by: GDN <96800819+GDNgit@users.noreply.github.com>
Co-authored-by: S34N <12197162+S34NW@users.noreply.github.com>

code/modules/events/blob/blob_mobs.dm

@@ -20,6 +20,14 @@
 	fire_damage = 3
 	var/mob/camera/blob/overmind = null
 
+/mob/living/simple_animal/hostile/blob/Initialize(mapload)
+	. = ..()
+	GLOB.blob_minions |= src
+
+/mob/living/simple_animal/hostile/blob/Destroy()
+	GLOB.blob_minions -= src
+	return ..()
+
 /mob/living/simple_animal/hostile/blob/proc/adjustcolors(a_color)
 	if(a_color)
 		color = a_color

code/modules/events/blob/blob_powers.dm

@@ -469,7 +469,7 @@
 	for(var/obj/structure/blob/BL in GLOB.blobs)
 		BL.adjustcolors(blob_reagent_datum.color)
 
-	for(var/mob/living/simple_animal/hostile/blob/BLO)
+	for(var/mob/living/simple_animal/hostile/blob/BLO in GLOB.blob_minions)
 		BLO.adjustcolors(blob_reagent_datum.complementary_color)
 
 	to_chat(src, "Your reagent is now: <b><font color=\"[blob_reagent_datum.color]\">[blob_reagent_datum.name]</b></font> - [blob_reagent_datum.description]")

code/modules/events/blob/theblob.dm

@@ -2,6 +2,7 @@
 
 GLOBAL_LIST_EMPTY(blobs)
 GLOBAL_LIST_EMPTY(blob_nodes)
+GLOBAL_LIST_EMPTY(blob_minions)
 
 /obj/structure/blob
 	name = "blob"

code/modules/events/undead_event.dm

@@ -8,7 +8,7 @@
 	RS.lightsoutAmount = pick(2,2,3)
 	RS.start()
 	RS.kill()
-	for(var/area/A)
+	for(var/area/A in GLOB.all_areas)
 		if(!is_station_level(A.z)) continue //Spook on main station only.
 		if(A.luminosity) continue
 //			if(A.lighting_space) continue

code/modules/maptext_alerts/location_blurbs.dm

@@ -118,7 +118,7 @@
 
 	var/atom/movable/screen/text/blurb/location_blurb = new()
 	if(antag_check.antag_datums)
-		for(var/datum/antagonist/role)
+		for(var/datum/antagonist/role in antag_check.antag_datums)
 			if(role.custom_blurb())
 				location_blurb.blurb_text = uppertext(role.custom_blurb())
 				location_blurb.text_color = role.blurb_text_color

code/modules/station_goals/bsa.dm

@@ -22,7 +22,7 @@
 /datum/station_goal/bluespace_cannon/check_completion()
 	if(..())
 		return TRUE
-	for(var/obj/machinery/bsa/full/B)
+	for(var/obj/machinery/bsa/full/B in GLOB.machines)
 		if(B && !B.stat && is_station_contact(B.z))
 			return TRUE
 	return FALSE

tools/ci/check_grep2.py

@@ -133,6 +133,19 @@ def check_tgui_ui_new_argument(idx, line):
     if "\tui = new" in line and not TGUI_UI_NEW.search(line):
         return [(idx + 1, "Invalid argument within constructor, please make sure window sizing is in corresponding JavaScript file.")]
 
+# checks for any (for var/type/x) loops that are not looping over bare datums: enforcing that the only case we will see this is if you genuinely want to loop over all datums in memory
+FOR_ALL_DATUMS = re.compile(r"for\s*\(\s*var\/((\w+)(?:(?:\/\w+){2,})?)\)")
+# double-checks that we don't have any attempts at looping like for(var/atom/a)
+FOR_ALL_NOT_DATUMS = re.compile(r"for\s*\(\s*var\/((?:atom|area|turf|obj|mob)(?:\/\w+))\)")
+def check_datum_loops(idx, line):
+    if FOR_ALL_DATUMS.search(line) or FOR_ALL_NOT_DATUMS.search(line):
+        return Failure(
+            idx + 1,
+            # yes this will concatenate the strings, don't look too hard
+            "Found a for loop without explicit contents. If you're trying to loop over everything in the world, first double check that you truly need to, and if so specify \'in world\'.\n"
+            "If you're trying to check bare datums, please ensure that your value is only cast to /datum, and please make sure you use \'as anything\', or use a global list instead."
+        )
+
 CODE_CHECKS = [
     check_space_indentation,
     check_mixed_indentation,
@@ -144,6 +157,7 @@ CODE_CHECKS = [
     check_conditional_spacing,
     check_global_list_empty,
     check_tgui_ui_new_argument,
+    check_datum_loops,
 ]