When upgrading to the new version, I get an error during startup:

Failed to load mods: ...eEckelmonster-core-library__/libs/utils/string-utils.lua:63: attempt to call field 'debug' (a nil value)
stack traceback:
    ...eEckelmonster-core-library__/libs/utils/string-utils.lua:63: in function 'is_string_valid'
    __TheEckelmonster-core-library__/libs/mod-data/mod-data.lua:8: in function 'create'
    __all-seeing-satellite__/prototypes/mod-data.lua:6: in main chunk
    [C]: in function 'require'
    __all-seeing-satellite__/data-final-fixes.lua:2: in main chunk

Hello! Apologies for the issue, but thanks for the report.

When you say you're getting this error during startup, is it when the game is trying to load to the main menu, or when trying too load a save?

Also, do you have any other mods present, specifically mods adding other planets?

When the game is trying to load to the main menu (you can also see the original file being data-final-fixes, which wouldn't be executed in the control stage).

I have quite a lot active mods, so it won't be easy to narrow things down...

base
elevated-rails
quality
space-age
0-event-trace
aai-loaders
Accumulator-V2
accumulator-wagon-reborn
AdditionalPasteSettings
adjustable_cannon_turret
AdvancedArtilleryRemotesContinued
Age-of-Production
Age-of-Production-Graphics
agri-tower-mk2
agricultural-revolution
agricultural-tower-extended-controls
agricultural-tower-placement-helper
alien-biomes-graphics
all-seeing-satellite
alt-alt-mode
Ammonia-carbon-fiber
AncientDrill
any-planet-start
aquilo-thermometer
armoredWall
ArmouredBiters
artificial-tree-soil
artillery-visibility-2_0
assault_spidertron_V2
asteroid_reprocessing_productivity
astroponics
ATP
AutoDeconstruct
AutoGhostBuilder
AutomatedCrushers
automatic-discharge-defense
automatic-underground-pipe-connectors
AutoSwitchTechs
auto_manual_mode
ballistic_missile
BarrelFluidIcons
barreling-group2
battery-powered
belt-visualizer
beltcounter2
BeltThreadUpgrades
Belt_Glow
better-asteroid-resistance
better-scrap-stacking
better-victory-screen
Better_Starmap_Background
BigRoboport
biochemistry
biome-mood-lighting
bioprocessing-tab
biouranium
biter-cleanup
blueprint-sandboxes
BlueprintTools
boompuff-agriculture
bp-trees
brake-squeal
bricked-foundry
BuggisNuclearBots
building-inserts-modules
bullet-trails
buoyant-spidertrons
calcite-casting
CalciteProcessingUnlocksSteamTurbine
camedo-snapmine
cargo-bay-inserters
cargo-ships
cargo-ships-graphics
cast-engines
Cerys-Moon-of-Fulgora
ch-concentrated-solar
change-recipe-quality-without-re-selecting-recipe
circuit-tracer
circuit_visualizer
ColloquialNames
colorful_biochamber
CombatRobotsOverhaul
combinator-codify
Combo-Technology
common-prototypes
common-prototypes-graphics
compaktcircuit
configurable-quality-buttons
ConstructionPlannerContinued
corrundum
cubium
CursorEnhancements
custom
custom-map-colors
data-utils
decider-combinator-output-constant-editor
deconstruction-planner-toggle-entity-with-pipette
demolisher-agriculture
demolisher-eggs
dim_lamps
diode-combinator
discovery_tree
display-panel-can-display-circuit-amount-as-text
Diversitree
doeworks-deer
dqol-resource-monitor
dredgeworks
dredgeworks-graphics
dw-frozen-reaches
dynamic-robot-queues
EarlyHeating
EasyLogisticConfiguration
EditorExtensions
ee-hidden
electric-refrigerated-wagon
electric-trains
ElectricHeatingTowerFixed
ElectricTrains
elevated-pipes
elevated-rails-recolor
enhanced-walls
EntangledBelts
entity-symmetry
even-distribution
expandtooltip
factorio-dz-tweaks
factoryplanner
FactorySearch
fall-of-promethea
FasterTankTurret
fdsl
Fill4Me
filter-combinator-improved
filter-copy-expansion
FilterHelper
fire-lights
fish-breeding-everywhere
fission-thruster
fixed-smarter-belt-immunity
Flare Stack
flib
floor-placer
Flow Control
FluidMustFlow
fluroflux
flushable-fluid-wagons
focused-rocket-turret
folk-shuttle
foundry-expanded
Fridge
fusion-thruster
FusionPoweredRobots
Fusion_Atomic_Robots
ghost-counter
glebaadditions
glebamodpatch
gleba_darker_deepwater
glutenfree-equipment-train-stop
gradual-nuke-destruction
graph_logs
greener_artifical_yumako_soil
GUI_Unifyer_Unified
gun-range-visualizer
gvv
halo-scarab
heat-inserter
heat-sensor
HeatPumps
heat_glow
hexalith-fix
HideResourceTool
Hovercrafts
hub-extensions
ICastBullets
InductionChargingRevamp
IndustrialRevolution3Assets1
IndustrialRevolution3Assets2
IndustrialRevolution3Assets3
IndustrialRevolution3Assets4
inks-repair-packs
InlaidLampsExtended
inserter-throughput
InserterVisualizerLite
integratedCircuitryFixed
Inter-Platform-Logistics
intercontinental-rocketry-forked
IntraOrbitalTransferChutes
inventory-repair
inventory-selector
inventory-sensor-improved
IR3_Assets_assembling_machines
IR3_Assets_some_assembly_required
K1_Advanced_storage_continued
k2-greenhouse-plus
kj_laser
kj_vehicles
Krastorio2Assets
kry-space-platform-chests
kry-vehicle-grids
kry_stdlib
Kux-CoreLib
Kux-GuiLib
lane-balancers
lane-filtered-loaders
lane-splitters
laser_rifle
ldinc_railgun_artillery
Legendary_Quality_science_pack_requirements
less-freezing
lex-aircraft
lightning-collector-equipment
lilys-cubeine
lilys-cubeine-asset-pack
lilys-cubeine-asset-pack-2
lilys-incendiaries
lilys-injector
lilys-mm
lilys-radar-shell
lilys-rtg-radar
lo-combinator-defaults
lo-recipe-combinator
lo-virtual-signals
LogiNetChannels
logistic-helper
logistics-insights
long_stack_inserter
machine-upgrades
map-tag-generator
maraxis-recipe-tweaks
maraxsis
metal-and-stars
metal-and-stars-graphics
metal-and-stars-graphics-2
Milestones
mining-patch-planner
MITWCHaatT
mklv-exclusive-soil-placement
mklv-lib
modular-beacon-power
module-calibrator
ModuleInserterEx
ModuleSwitcherAttachment
momentum
more-quality-scaling
naked-rails-f2
Nearby-Fuel-Amount
neural-spider-control
new-diagonal-inserter
NicerFuelGlow-Fixed
NightvisionOverhaulSpaceAge
nixie-tubes
OilOutpostPlanner
omni
orbital-interlink
orbital-transfer
ore-scaling
osha_container_signals
osha_hot_swap
osha_launch_control
osha_smarter_pasting
overgrowth-on-nuclear-ground
P2P-automation
P2P-Transfer
Paracelsin
Paracelsin-Graphics
particle-physics
passive-power-combinators
paste-logistic-settings-continued
PasteMoreLogisticSettings
PerfectPump
personal-thunder-strike-defense
PersonalTeslaDefenseEquipment
petroleum_jelly
Pi-C_lib
PipeVisualizer-Updated
planet-hexalith
planet-request-group
planet-request-group-simplified
PlanetaryFuels
planets-have-flow-statistics-for-their-cargo-pods
PlanetsLib
plasma-duct
plasma_crafter
plated_floor
playtime-plus
preserve-products-produced
prismatic-quality
productivity-technology-limit
pulse-laser-turret
pump
PumpOnLandfill
pushbutton
qol_research
quality-holmium-ore-returns-more-holmium-solution
quality-seeds
quality-upgrade-planner
QualityOfLifeNukes
QualityShortcutFix
radar-equipment
RateCalculator
raven_mk2
realistic-trains
rebuild-crash-site
rec-blue-plus
remote-view-flashlight
Repair_Turret
resourcehighlighter-dark
reusable-rocket-simple
RobotVehicleDeployment
RocketCargoInsertion
rocks-heal-over-time-just-like-trees
rubia
rubia-assets
runtime-spoilage-library
sa-repair-turret
SA-Scorpion
Sane-Concrete-2
science-pack-dependencies
scrap-reprocessor
secretas
shchierbin
shield-projector
shortwave_fix_limited
show-fluid-temperature-in-pipe-and-tank-gui
signal-display
silo-chest
simple-mod-reload
simple_refrigerator
simple_wood_to_coal
skewer_planet_vesta
skewer_planet_vesta_assets
smaller-shortcut-icons
smart-deconstruction-planner
SmartCannonShells
SmoothWarnings
smooth_platform_walls
snouz_better_asteroid_collector
snouz_long_electric_gun_turret
SolarMatrix
space-platform-for-ground
space-platform-graveyard
space-spidertron
SpaceMines
spider-launcher
SpidertronEnhancements
SpidertronPatrols
spoilage-scanner
stackable-asteroids
stirling-generator
StoneFromOxide
storage-roboport
Surfaces-Have-Temperature
tarantulator
TaskList
TechTreeColors
temporary-blocking-entities
Testbenchcontrols
textplates
TheEckelmonster-core-library
thinking_brain
thruster-control-behavior
thruster-plasma-duct
Thrusters-over-thrusters
Todo-List
toggle-foundation
toolbars-mod
train-loader
TrainSkipFulfilledStation2
transparent-elevated-rails
tree-healing
Tree_XRay
underground-heat-pipe
UndergroundIndicatorsFixed
upgrade-planner-toggle-entity-with-pipette
vacuum-cleaner
valerian-planets
valves
Various_Asteroid_Grabbers
Various_Cargo_Bays
vehicle-control-center
vehicle-corpses
virtual-signals2
visible-planets
weapon_quality
what-items-do-i-have
WireShortcutX
wood-universe-assets
ZElectricVehiclesQF
zeus-wrath
zithorian-extra-storage-tanks-port

(a few of these are unpublished local mods, and some others have been modified, but none of that should interfere in any way with your logging)

Ahh good point on the data-final-fixes! (didn't register with me at first for some reason).

Thanks for sharing your mod list. Honestly not sure at the moment what the issue could be, but I am certainly looking into it.

Just want to check though, can you load to the main menu when no other mods are present except for this one (and its dependency)?

I'm not sure how non local variables are handled at the data stage, but I'd assume that the issue is that the Log variable is set to something unexpected when string-utils.lua is required.
I couldn't immediately find anything about whether global variables from other mods or earlier data stage might be still visible...

I printed out a serialized version of the Log variable just before the error occurred:

{
  __inGame = true,
  __index = "SERPENT PLACEHOLDER",
  __lastTick = -1,
  __logTick = false,
  __name = "lang.Log",
  __on = true,
  append = ((loadstring or load)("\27LuaR\0\1\4\8\4\8\0\25?\13\n\26\n1\0\0\0>\0\0\0\1\0\6*\0\0\0D\0\0\0?\0@\0?\0\0\0??\0\1\24@@\1\23@\0?@\0\0\0\23\0\4??\0@\0?\0\0\0??\0\1\24?@\1\23?\1???@\0?\0A\1?\0\0\0\11A\0\0\n??????\1@\0\0\1\23?\0???A\0?\0\0\0??\0\1@\0\0\1?\0B\0?@B\1?\0\0\0\23\0\2???B\0??B\1?\0?\0\11A\0\0FAC\0G??2G??2\nA\1??@?\1?\0D\0?\0?\0?@\0\1\31\0?\0\17\0\0\0\4\5\0\0\0\0\0\0\0type\0\4\9\0\0\0\0\0\0\0userdata\0\4\6\0\0\0\0\0\0\0table\0\4\8\0\0\0\0\0\0\0serpent\0\4\6\0\0\0\0\0\0\0block\0\4\8\0\0\0\0\0\0\0comment\0\1\0\4\9\0\0\0\0\0\0\0tostring\0\4\4\0\0\0\0\0\0\0Log\0\4\9\0\0\0\0\0\0\0__inGame\0\4\5\0\0\0\0\0\0\0game\0\4\6\0\0\0\0\0\0\0print\0\4\5\0\0\0\0\0\0\0skip\0\4\8\0\0\0\0\0\0\0defines\0\4\11\0\0\0\0\0\0\0print_skip\0\4\6\0\0\0\0\0\0\0never\0\4\4\0\0\0\0\0\0\0log\0\0\0\0\0\1\0\0\0\0\0\31\0\0\0\0\0\0\0@__toolbars-mod__/lang/Log.lua\0*\0\0\0002\0\0\0003\0\0\0003\0\0\0003\0\0\0003\0\0\0003\0\0\0004\0\0\0004\0\0\0005\0\0\0005\0\0\0005\0\0\0005\0\0\0005\0\0\0006\0\0\0006\0\0\0006\0\0\0006\0\0\0006\0\0\0006\0\0\0006\0\0\0006\0\0\0008\0\0\0008\0\0\0008\0\0\0008\0\0\0:\0\0\0:\0\0\0:\0\0\0:\0\0\0;\0\0\0;\0\0\0;\0\0\0;\0\0\0;\0\0\0;\0\0\0;\0\0\0;\0\0\0;\0\0\0=\0\0\0=\0\0\0=\0\0\0>\0\0\0\2\0\0\0\8\0\0\0\0\0\0\0message\0\0\0\0\0*\0\0\0\6\0\0\0\0\0\0\0entry\0\1\0\0\0*\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0_ENV\0",'@serialized')),
  log = ((loadstring or load)("\27LuaR\0\1\4\8\4\8\0\25?\13\n\26\n!\0\0\0-\0\0\0\1\0\5\31\0\0\0F\0@\0G@?\0[\0\0\0\23@\6?F\0@\0G??\0[\0\0\0\23@\4?F?@\0G\0?\0?\0@\0?@A\1\25@\0\1\23?\2??\0@\0??A\1??\1\0?@\0\1?\0@\0??A\1?\0\2\0\0\1?\0?0?\1?@\0\1?\0@\0?@??F\0@\0G??\0?\0\0\0]@\0\1\31\0?\0\9\0\0\0\4\4\0\0\0\0\0\0\0Log\0\4\5\0\0\0\0\0\0\0__on\0\4\n\0\0\0\0\0\0\0__logTick\0\4\5\0\0\0\0\0\0\0game\0\4\5\0\0\0\0\0\0\0tick\0\4\11\0\0\0\0\0\0\0__lastTick\0\4\7\0\0\0\0\0\0\0append\0\4\1\0\0\0\0\0\0\0\0\4\7\0\0\0\0\0\0\0Tick: \0\0\0\0\0\1\0\0\0\0\0\31\0\0\0\0\0\0\0@__toolbars-mod__/lang/Log.lua\0\31\0\0\0\"\0\0\0\"\0\0\0\"\0\0\0\"\0\0\0#\0\0\0#\0\0\0#\0\0\0#\0\0\0$\0\0\0$\0\0\0%\0\0\0%\0\0\0%\0\0\0%\0\0\0&\0\0\0&\0\0\0&\0\0\0&\0\0\0'\0\0\0'\0\0\0'\0\0\0'\0\0\0'\0\0\0'\0\0\0(\0\0\0(\0\0\0+\0\0\0+\0\0\0+\0\0\0+\0\0\0-\0\0\0\2\0\0\0\8\0\0\0\0\0\0\0message\0\0\0\0\0\31\0\0\0\5\0\0\0\0\0\0\0tick\0\n\0\0\0\26\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0_ENV\0",'@serialized')),
  logMethod = ((loadstring or load)("\27LuaR\0\1\4\8\4\8\0\25?\13\n\26\n\14\0\0\0\18\0\0\0\0\0\5\18\0\0\0\6\0@\0\7@@\0A?\0\0??\0\0\29??\1\27\0\0\0\23?\0?G\0A\0[@\0\0\23\0\0?A@\1\0??A\0??A\1?\0?\0\1\1\2\0?0?\1?@\0\1\31\0?\0\9\0\0\0\4\6\0\0\0\0\0\0\0debug\0\4\8\0\0\0\0\0\0\0getinfo\0\3\0\0\0\0\0\0\0@\4\2\0\0\0\0\0\0\0n\0\4\5\0\0\0\0\0\0\0name\0\4\8\0\0\0\0\0\0\0unknown\0\4\4\0\0\0\0\0\0\0Log\0\4\4\0\0\0\0\0\0\0log\0\4\3\0\0\0\0\0\0\0()\0\0\0\0\0\1\0\0\0\0\0\31\0\0\0\0\0\0\0@__toolbars-mod__/lang/Log.lua\0\18\0\0\0\15\0\0\0\15\0\0\0\15\0\0\0\15\0\0\0\15\0\0\0\16\0\0\0\16\0\0\0\16\0\0\0\16\0\0\0\16\0\0\0\16\0\0\0\17\0\0\0\17\0\0\0\17\0\0\0\17\0\0\0\17\0\0\0\17\0\0\0\18\0\0\0\2\0\0\0\5\0\0\0\0\0\0\0info\0\5\0\0\0\18\0\0\0\5\0\0\0\0\0\0\0name\0\11\0\0\0\18\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0_ENV\0",'@serialized')),
  logTick = ((loadstring or load)("\27LuaR\0\1\4\8\4\8\0\25?\13\n\26\n\9\0\0\0\11\0\0\0\0\0\2\6\0\0\0\6\0@\0\7@@\0F?@\0G??\0\29@\0\1\31\0?\0\4\0\0\0\4\4\0\0\0\0\0\0\0Log\0\4\4\0\0\0\0\0\0\0log\0\4\5\0\0\0\0\0\0\0game\0\4\5\0\0\0\0\0\0\0tick\0\0\0\0\0\1\0\0\0\0\0\31\0\0\0\0\0\0\0@__toolbars-mod__/lang/Log.lua\0\6\0\0\0\n\0\0\0\n\0\0\0\n\0\0\0\n\0\0\0\n\0\0\0\11\0\0\0\0\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0_ENV\0",'@serialized')),
  logTrace = ((loadstring or load)("\27LuaR\0\1\4\8\4\8\0\25?\13\n\26\n\21\0\0\0\23\0\0\0\0\0\2\7\0\0\0\6\0@\0\7@@\0F?@\0G??\0]\0?\0\29@\0\0\31\0?\0\4\0\0\0\4\4\0\0\0\0\0\0\0Log\0\4\4\0\0\0\0\0\0\0log\0\4\6\0\0\0\0\0\0\0debug\0\4\n\0\0\0\0\0\0\0traceback\0\0\0\0\0\1\0\0\0\0\0\31\0\0\0\0\0\0\0@__toolbars-mod__/lang/Log.lua\0\7\0\0\0\22\0\0\0\22\0\0\0\22\0\0\0\22\0\0\0\22\0\0\0\22\0\0\0\23\0\0\0\0\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0_ENV\0",'@serialized')),
  logTraceWith = ((loadstring or load)("\27LuaR\0\1\4\8\4\8\0\25?\13\n\26\n\27\0\0\0\29\0\0\0\1\0\5\n\0\0\0F\0@\0G@?\0?\0\0\0??\0\0\6?@\0\7\1A\2\29??\0?\0\1\1]@\0\1\31\0?\0\5\0\0\0\4\4\0\0\0\0\0\0\0Log\0\4\4\0\0\0\0\0\0\0log\0\4\2\0\0\0\0\0\0\0\n\0\4\6\0\0\0\0\0\0\0debug\0\4\n\0\0\0\0\0\0\0traceback\0\0\0\0\0\1\0\0\0\0\0\31\0\0\0\0\0\0\0@__toolbars-mod__/lang/Log.lua\0\n\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\28\0\0\0\29\0\0\0\1\0\0\0\7\0\0\0\0\0\0\0prefix\0\0\0\0\0\n\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0_ENV\0",'@serialized'))
}

Apparently, Log gets overwritten by the toolbars mod...

And yes, with only space age and 0.7.1 of your mod (and dependencies), factorio does load successfully.

Thank you for the confirmation. And thank you for tracking down which mod is causing the incompatibility - hadn't quite figured out which one it was yet from the mod list you provided (thanks again).

I've been able to recreate the issue as well now. Will be looking into it more and hope to have a fix out as soon as I can.

With the release of version 0.1.1 of TheEckelmonster-core-library, this issue should be fixed.

Please do let me know if you encounter any other problems or issues.

Thanks again for the help troubleshooting - greatly appreciate it!

Thank you!