Fix renamed/removed unit images in MP Aethermaw (wesnoth#8432)

Playing the multiplayer scenario Aethermaw as Loyalists vs. Undead
revealed some image errors:

    20240219 06:50:21 error image: could not open image 'units/undead/shadow-s-attack-1.png'
    20240219 06:50:21 error image: could not open image 'units/undead/shadow-s-attack-4.png'
    20240219 06:50:21 error image: could not open image 'units/undead/shadow-n-3.png'
    20240219 06:50:22 error image: could not open image 'units/undead/shadow-n-attack-2.png'
    20240219 06:50:26 error image: could not open image 'units/human-loyalists/spearman-attack-se-9.png'
    20240219 06:50:26 error image: could not open image 'units/human-loyalists/spearman-attack-se-10.png'
    20240219 06:50:26 error image: could not open image 'units/human-loyalists/spearman-attack-s-6.png'
    20240219 06:50:26 error image: could not open image 'units/human-loyalists/general-idle-5.png'

units/undead/shadow-* images were moved to units/undead-spirit/shadow-*
in 1.17.4 commit a2ad3ae, specifically the "1.17 undead sprite
cleanup" commit 961b8a3 of PR wesnoth#6655.  This was documented on the
forums:
https://forums.wesnoth.org/viewtopic.php?p=684291&hilit=units%2Fundead-spirit%2F#p684291

wmllint handles renamed images, but it also makes an enormous number of
other (often questionable at best) changes (issue wesnoth#5799).  So for now,
instead of using wmllint, just update Aethermaw for these renamed images
as follows (requires GNU sed):

    git grep -Fl -- 'units/undead/shadow-' \
        | grep -v '^data/tools/wmllint$' \
        | xargs sed -i 's|units/undead/shadow-|units/undead-spirit/shadow-|'

These units/human-loyalists/ images were removed in 1.17.12 commit
8e38cfd, specifically the "spearman image cleanup" commit 775e7f8
and the "remove left-over old general frames" commit e07d554 in
PR wesnoth#7208.  But Aethermaw still uses them.

Restore the removed images that are still used:

    git grep -EIh -- '^[^#]*[{]PLACE_IMAGE[^ ]* +[(]?"?[^{}$ ~")]+[ ~")].*$' data/ \
        | sed -E 's|^.*[{]PLACE_IMAGE[^ ]* +[(]?"?([^{}$ ~")]+)[ ~")].*$|\1|' \
        | while read -r img; do
            [ -e data/core/images/${img} ] && continue
            [ -e data/campaigns/*/images/${img} ] && continue
            [ -e ${img} ] && continue
            git show 8e38cfd~1:data/core/images/${img} 1>data/core/images/${img}
        done

Also add a CI check to prevent this from happening in the future.
Example output without these Aethermaw fixes:

    data/multiplayer/scenarios/2p_Aethermaw.cfg:134: missing image: units/undead/shadow-s-attack-1.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:135: missing image: units/undead/shadow-n-attack-2.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:147: missing image: units/undead/shadow-n-3.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:149: missing image: units/undead/shadow-s-attack-4.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:196: missing image: units/human-loyalists/spearman-attack-se-10.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:197: missing image: units/human-loyalists/spearman-attack-s-6.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:198: missing image: units/human-loyalists/spearman-attack-se-9.png
    data/multiplayer/scenarios/2p_Aethermaw.cfg:203: missing image: units/human-loyalists/general-idle-5.png

.github/workflows/ci-main.yml

@@ -31,6 +31,9 @@ jobs:
       - name: Whitespace and WML indentation check
         if: success() || failure()
         run: ./utils/CI/fix_whitespace.sh; git status; git diff --exit-code
+      - name: WML missing images check
+        if: success() || failure()
+        run: utils/CI/check_wml_images.sh
       - name: Run luacheck
         if: success() || failure()
         run: luacheck .

changelog_entries/aethermaw_image_errors.md

@@ -0,0 +1,2 @@
+ ### Multiplayer
+   * Fix renamed Undead images and removed Loyalist images in Aethermaw (issue #8432)

data/multiplayer/scenarios/2p_Aethermaw.cfg

@@ -131,8 +131,8 @@
         {PLACE_IMAGE "units/goblins/wolf-rider-moving.png~FL()~RC(magenta>1)" 48 2}
         {PLACE_IMAGE "units/goblins/wolf-rider-moving.png~FL()~RC(magenta>1)" 46 2}
 
-        {PLACE_IMAGE "units/undead/shadow-s-attack-1.png~RC(magenta>5)" 44 18}
-        {PLACE_IMAGE "units/undead/shadow-n-attack-2.png~RC(magenta>5)" 45 24}
+        {PLACE_IMAGE "units/undead-spirit/shadow-s-attack-1.png~RC(magenta>5)" 44 18}
+        {PLACE_IMAGE "units/undead-spirit/shadow-n-attack-2.png~RC(magenta>5)" 45 24}
         {PLACE_IMAGE "units/undead-skeletal/revenant/revenant-attack-4.png~RC(magenta>5)" 45 21}
         {PLACE_IMAGE "units/undead-skeletal/chocobone-attack-2.png~RC(magenta>5)" 45 18}
         {PLACE_IMAGE "units/undead-skeletal/chocobone-attack-2.png~RC(magenta>5)" 43 22}
@@ -144,9 +144,9 @@
         {PLACE_IMAGE "units/undead-necromancers/ancient-lich-magic-1.png~FL()~RC(magenta>5)" 48 17}
         {PLACE_IMAGE "units/undead/zombie-troll-attack.png~RC(magenta>5)" 45 19}
         {PLACE_IMAGE "units/undead/zombie-troll-attack-n.png~RC(magenta>5)" 49 25}
-        {PLACE_IMAGE "units/undead/shadow-n-3.png~FL()~RC(magenta>5)" 49 23}
+        {PLACE_IMAGE "units/undead-spirit/shadow-n-3.png~FL()~RC(magenta>5)" 49 23}
         {PLACE_IMAGE "units/undead/ghoul-attack-2.png~RC(magenta>5)" 46 22}
-        {PLACE_IMAGE "units/undead/shadow-s-attack-4.png~RC(magenta>5)" 43 21}
+        {PLACE_IMAGE "units/undead-spirit/shadow-s-attack-4.png~RC(magenta>5)" 43 21}
         {PLACE_IMAGE "units/undead/zombie-dwarf-attack-n.png~RC(magenta>5)" 48 24}
         {PLACE_IMAGE "units/undead/zombie-dwarf-attack-n.png~RC(magenta>5)" 48 23}
         {PLACE_IMAGE "units/undead/zombie-dwarf-attack-n.png~RC(magenta>5)" 47 25}

utils/CI/check_wml_images.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+#
+# Find missing images referenced by WML (as in issue #8432)
+#
+# Requires sort with -s option (stable sort, disable further byte-by-byte
+# comparison of lines that collate equally by specified sort key), e.g. from
+# GNU coreutils
+#
+# Example output:
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:134: missing image: units/undead/shadow-s-attack-1.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:135: missing image: units/undead/shadow-n-attack-2.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:147: missing image: units/undead/shadow-n-3.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:149: missing image: units/undead/shadow-s-attack-4.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:196: missing image: units/human-loyalists/spearman-attack-se-10.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:197: missing image: units/human-loyalists/spearman-attack-s-6.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:198: missing image: units/human-loyalists/spearman-attack-se-9.png
+#     data/multiplayer/scenarios/2p_Aethermaw.cfg:203: missing image: units/human-loyalists/general-idle-5.png
+
+set -eu
+
+# Parsing WML with a regular expression isn't ideal, but it's easy and it works.
+IMG_RE='^[^#]*[{]PLACE_IMAGE[^ ]* +[(]?"?([^{}$ ~")]+)[ ~")].*$'
+
+# In `! { COMMANDS | grep -- '.'; }` below, `grep -- '.'` returns a successful
+# exit status if `COMMANDS` produce output, and `!` inverts it into an error
+# status.  A less clever/obscure solution would be `es=true` before the loop,
+# `es=false` inside the loop after all the `continue`s, and `${es}` at the end;
+# but that won't work because all commands in pipelines run in subshells that
+# can't affect variables in the parent shell.
+
+! { git grep -EIn -- "${IMG_RE}" data/ | while IFS=':' read -r wml ln img; do
+	img="$(printf '%s' "${img}" | sed -E "s|${IMG_RE}|\\1|")"
+	[ -e "data/core/images/${img}" ] && continue
+	[ -e "${img}" ] && continue
+	case "${wml}" in
+		data/campaigns/*)
+			sfx="${wml#data/campaigns/*/}"
+			[ -e "${wml%/${sfx}}/images/${img}" ] && continue
+			;;
+	esac
+	printf '%s:%d: missing image: %s\n' "${wml}" "${ln}" "${img}"
+done | sort -t ':' -k 2n,2n | sort -t ':' -k 1,1 -s | grep -- '.'; }