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Error Messages

TL;DR

Paste the message you got into the search box. Every message the mod throws by name is listed here with its cause and its fix.

Messages are quoted exactly as the mod produces them, with <...> marking a value the mod substitutes. Every entry was taken from the source, not from bug reports. code review

Most of this page is 7.4.12. Version 7.5.1 has 36 messages that 7.4.12 does not, and removes none of the older ones. All 36 come from the new road and highway planners. They are in Messages added in 7.5. code review

Where these appear

None of these strings are written to a file by the mod as a matter of course. They reach you in one of two ways, and the difference decides which file to open. code review

Thrown during chunk generation

The game does not crash. This is the single most important thing to know about every message on this page that comes from generation. game test

LostCityFeature wraps the generation of a chunk in a try block that catches Exception. When anything throws, the mod logs Error generating chunk <x>,<z>: <message>, prints the stack trace, and carries on with the next chunk. code review

The catch is narrower than the method, and outside it the game does crash

The guarded region is the call to LostCityTerrainFeature.generate and nothing else. Three things happen before it, unguarded:

  1. getDimensionInfo, which resolves the profile and, through it, the profile's worldStyle and outside style
  2. the biome lookup for the chunk
  3. setWorld on the dimension info code review

A throw in any of those leaves LostCityFeature entirely, reaches vanilla's feature placer, and produces a genuine crash with a Description: Feature placement crash report in crash-reports/. game test

The realistic way to hit this is a profile naming a worldStyle that no loaded datapack defines, which is easy to do by editing a datapack and forgetting the profile, or the reverse: game test

java.lang.RuntimeException: Error getting resource mypack:mystyle!
  at DefaultDimensionInfo.<init>(DefaultDimensionInfo.java:44)
  at LostCityFeature.getDimensionInfo(LostCityFeature.java:90)
  at LostCityFeature.m_142674_(LostCityFeature.java:49)
Caused by: java.lang.NullPointerException: Cannot invoke
  "WorldStyleRE.getRegistryName()" because "object" is null

The tell is the line number on m_142674_. 49 is the unguarded setup and crashes. 62 is inside the catch and does not. Confirmed in game on 7.4.12. code review

So the rule is: a mistake in your assets fails chunks and logs. A mistake in the wiring between profile and datapack crashes. game test

On a sphere landscape the catch is not there at all

The mod registers a second feature, LostCitySphereFeature, and that class contains no try anywhere. It runs Spheres.generateSpheres, which reaches ChunkFixer and asks for a chunk's BuildingInfo, which is what evaluates part conditions. So the same fault that LostCityFeature catches and logs escapes when it arrives through the sphere feature instead.

It only runs when landscapeType is spheres, cavernspheres or space. On those, a building fault stops producing Error generating chunk lines and starts producing ReportedException: Feature placement instead. code review

Measured on 7.4.12 with one broken building: on default, 35 chunks failed, all caught. On spheres, the same pack gave 18 caught and 21 uncaught, and the server shut down. game test

If your log has Feature placement rather than Error generating chunk, check landscapeType before you look at anything else. game test

What actually happens game test
The game Keeps running. No crash report is written.
That chunk Is left partially generated. Terrain may be there with the buildings missing.
Its neighbours Often fail too. See below.
Every other chunk with the same fault Fails the same way, one log line each
In game Nothing tells you, beyond the world looking wrong
File to open logs/latest.log. Not crash-reports/, because none is produced.

Verified by running it: a datapack with an empty bridges selector produced 1842 Error generating chunk lines in a single session, and the game never crashed. game test

The same catch is present in 7.4.12, 7.5.1, 8.4.1 and 10.0.1, so this applies to every version this wiki covers. code review

One broken building takes its neighbours down with it

A chunk does not only generate itself. To shape terrain at its edges, to lay railways, and to spread debris, it asks the chunks around it for their BuildingInfo, and building that info is what evaluates the part conditions. So a building that throws fails every chunk that looks at it, not only the chunk it stands in.

The reach is much larger than one chunk, because those queries chain. getDesiredMaxHeightL2 calls getDesiredMaxHeightL1 on a neighbour, which queries its own neighbours in turn. game test

Measured on 7.4.12: 3 broken buildings produced 77 failed chunks, spread over a 13 by 10 chunk area. Two of the three stood 6 chunks apart, and the failures joined into one continuous region. game test

The practical consequence when you are diagnosing: the coordinates in Error generating chunk x,z are usually not where your mistake is. They are where something asked about it. Look for the building the message names, or use the extent of the failed region to find its centre. game test

Which faults spread and which stay put

The split is where in generation the throw happens, and it decides how far from the message to look.

Fault Thrown while Spreads game test
A level matching no part, an empty selector, a bad range Building the chunk's BuildingInfo Yes. Neighbours build that same info.
An undefined palette character Placing blocks No. One chunk, one line.
A loot or mob name that is not a Condition The post-generation pass No. One chunk.

Measured in the same run: 3 buildings with uncovered levels took out 77 chunks, while a building with a circular palette alias standing 6 chunks away failed exactly 1, its own, and its four neighbours generated normally. game test

Volume is the real symptom, and the traces run out

A single misconfiguration produces one failure per affected chunk, so a short session can log thousands. After the first few, the JVM stops recording stack traces for a repeatedly thrown exception, and the remaining lines carry only the message, or null.

Read the earliest errors in the file. The recent ones are the least useful.

The Lost Cities - DevTool exists mostly because of this paragraph. It names the building and its chunk at the throw, where both are still known, so the volume stops mattering.

Generation is not the only place the mod throws. Anything thrown while a profile or an asset is being loaded, before generation starts, is outside that try and behaves like a normal crash. code review

In the log, the message appears as the exception line at the top of the stack trace: code review

java.lang.RuntimeException: Misconfiguration! Floor were generated for a building where no part condition matches!
    at mcjty.lostcities.worldgen.lost.BuildingInfo...

Search for the message text, then read down the trace. The frames below the mod's own classes tell you which chunk and which asset was being processed.

Logged warnings

A few failures are logged instead of thrown. The mod writes these through a log4j logger named lostcities, so they appear only in logs/latest.log and in the server console. They never produce a crash report, and nothing in game tells you they happened. code review

The line looks like this:

[Server thread/WARN] [lostcities/]: Cannot find 'mycity:my_street' in minecraft:root!

This is the quiet failure mode behind streets, parks, fountains, stairs, rail dungeons and building fronts that never appear. If content is missing and the game has not crashed, search latest.log for lostcities before you touch your JSON. code review

Grep the log rather than scrolling it

latest.log is large. On Windows, findstr /C:"lostcities" logs\latest.log is enough. The mod's own lines are the only ones carrying that logger name.

Palette errors

Could not find entry '<char>' in the palette for part '<part>'!

When: chunk generation. code review

A part used a character that the merged palette does not define. game test

The message names the part, not the palette, which misleads you when the fault is on the palette side. The causes, in order of likelihood: game test

Cause Fix code review
A typo in the part's slices, or a row of the wrong length shifting characters Check row lengths first. The mod never validates them.
The character is defined in a palette that is not in this building's chain Add it to the part's refpalette, or to the Style's palettes.
The character is a frompalette alias in a circular reference A cycle resolves to nothing and leaves the character undefined, with no warning at load. See How aliases resolve.
The character is a space and your style does not include the common palette " " maps to air because common defines it, not because the mod special-cases it.

Error getting resource <name>!

When: chunk generation, and for loot specifically during the post-generation pass, after every block is already placed. code review

A named asset is not in the mod's registry. The name in the message is exactly what you wrote, so the fault is a name that does not exist, a missing namespace, or the wrong kind of name. game test

Cause Fix code review
The profile's worldStyle names a World Style no loaded datapack defines This one crashes the game, because it is resolved before the catch. See above. Check that the profile and the datapack in the world are the same generation of your pack.
A palette loot or mob key holds a loot table or entity ID Both name a Condition. Wrap the value in a one-entry Condition and name that instead. This is by far the most common form.
A bare name that resolved into the minecraft namespace See Namespaces.
A genuine typo in an asset name Compare against the file name, which is the asset name.

For loot, the symptom does not look like an exception

The loot pass runs after placement, so the blocks are already in the world. What you see is a building whose chests can be opened, are empty, and render invisible, because their block entities were never completed. Nothing appears in chat. Confirmed in game on 7.4.12.

String index out of range: <n>

When: chunk generation, from a plain Java StringIndexOutOfBoundsException rather than a message the mod wrote. game test

A Part's layer holds fewer than xsize * zsize characters. The mod joins a layer's rows into one string and reads charAt(z * xsize + x), so the generator eventually asks for a position that is not there. game test

n is the position it wanted, and for a normal 16 by 16 part the number is 255, the last one. That number tells you nothing about which row is wrong. Count the characters in every row of the part, and remember that a row two short and another one long cancel out in the total while still smearing the layer. game test

Too many characters produces no message at all. See A wrong row length produces a diagonal smear. game test

Bad landscape type: <name>!

When: mod construction, before the server or the world exists. code review

landscapeType holds a value that is not one of the six accepted strings. The mod throws inside its constructor, so Forge reports Failed to create mod instance. ModID: lostcities and the game or server does not start at all. There is no world to look at and no chunk log to read. game test

The accepted values are lowercase: default, floating, space, spheres, cavern, cavernspheres. The enum inside the mod is uppercase, so copying the constant name out of a decompiler or a bug report gives you SPACE, which fails. See Landscape types. game test

Cannot read field "CITY_CHANCE" because ... getOutsideProfile() is null

When: chunk generation on a sphere landscape. code review

landscapeType is spheres or cavernspheres and the profile does not set cityspheres.outsideProfile. Everything outside a sphere has no profile to generate from, so the first chunk that asks about the outside world throws. game test

Because a sphere landscape runs through LostCitySphereFeature, which has no try, this is not a logged chunk failure. It escapes, and on a dedicated server it brought the server down. game test

Fix: set outsideProfile to the name of another profile whenever landscapeType is a sphere type. It is documented as optional with a default of "", but on those landscapes it is effectively required.

Invalid palette entry for '<char>'! Not enough blocks in the random list (factor should go up to 128)

When: the first time the mod compiles this palette, during generation. code review

A weighted list (blocks, or a referenced variant) has random weights totalling less than 128. The mod fills a fixed array of 128 slots and refuses a partially filled one. game test

Add a catch-all entry last with a large weight. The mod's own idiom is small honest numbers for the rare options, then something like 1000 at the end to fill the remainder. See The 128-slot rule.

Invalid palette entry for '<char>'!

When: the same point, for a different cause. The entry resolved to nothing usable. A variant name that does not exist is the usual reason. code review

Illegal palette <name>!

When: palette load. code review

An entry in that palette has none of block, variant, blocks or frompalette. Every entry needs exactly one of them. code review

Cannot find block: '<blockstate>'!

When: palette load. code review

A block, damaged, or weighted-list block string names a block that is not registered. Check the spelling and the namespace, and confirm that the mod providing the block is installed. If the string contains [...] state properties, a malformed property list throws a different and less readable parser exception instead. game test

Building and part errors

Misconfiguration! Floor were generated for a building where no part condition matches!

When: chunk generation. This is the most common error in the mod. game test

The mod picked a floor index and no entry in the building's parts matched it. game test

The rule is coverage, not declaring bounds. Every index from -cellars to +floors needs a matching part. The height comes from the Profile, and your building's own minfloors and maxfloors only clamp that unless you also set overrideFloors: true. So parts written for floors 0 to 2 work until the profile rolls 3. game test

Fix: add one part reference with no condition keys at all. It matches every level. See Floor coverage.

parts2 never causes this. It is a genuinely optional overlay. game test

NullPointerException in ChunkDriver.correct

When: chunk generation, the moment the mod places a door. Observed in a real world, not derived from reading code. game test

Error generating chunk -6,-8: Cannot invoke
  "net.minecraft.world.level.block.state.BlockState.m_60734_()" because "state" is null
    at mcjty.lostcities.worldgen.ChunkDriver.correct(ChunkDriver.java:253)
    at mcjty.lostcities.worldgen.ChunkDriver.add(ChunkDriver.java:289)
    at mcjty.lostcities.worldgen.gen.Doors.generateDoors(Doors.java:60)

The building's filler character did not resolve to a block. game test

Doors asks the building for its filler block and looks the character up in the building's palette. That palette is the Style's palettes plus the building's own refpalette or palette. A refpalette on a part is not in that set. code review

Cause Fix game test
The filler character is defined only in a palette that the building's parts reference Add the same refpalette to the building.
The character is not defined anywhere in scope Define it, or change filler to a character the style already provides.

This produces one failure per chunk, and most of them have no stack trace

Every affected chunk logs Error generating chunk <x>,<z>. After the first few, the JVM stops recording stack traces for a repeatedly thrown NullPointerException, so the rest log only null with no trace and no clue.

A log full of Error generating chunk ...: null with a handful of real traces near the top is this bug. Read the earliest errors in the file, not the most recent. game test

The chunks still generate. Terrain and streets appear, buildings are missing or partial, and nothing tells you in game. game test

NullPointerException on a null Character

When: chunk generation. Observed in a real world. code review

java.lang.NullPointerException: Cannot invoke "java.lang.Character.charValue()"
  because "corridorRoofBlock" is null
    at mcjty.lostcities.worldgen.gen.Corridors.generateCorridors

The name in the message tells you which character is missing. Others seen include CityStyle.getStreetBlock(). game test

The City Style in use does not define that character, and the generator dereferences it without checking. This only reaches you if your city style inherits nothing, because citystyle_common supplies the whole set. game test

Fix: inherit a style that defines them, or set all of them yourself. The full list is in City Style.

Expect to meet these one at a time. Each run fails on the first missing character it reaches, so fixing one exposes the next. game test

Cannot find support block '<char>' for highway part '<part>'!

When: chunk generation, on a highway over open ground. code review

The part's meta has a support character that the palette does not define. Either define the character, or remove the support meta. Without it the highway generates with no pillars, which is safe. See meta. code review

Cannot find rail block '<char>' for type '<type>'!

When: chunk generation, on a railway. code review

The city style's railblocks.railmain character is not in the palette for that chunk. Check that the character exists in every style a railway can pass through, not only your main one. game test

A part comes out smeared diagonally, with no error

This is not an exception. It is listed here because it is what the symptom gets searched for. A slices row that is not exactly xsize characters long shifts every block after it in that layer. The mod concatenates the rows and indexes them by position, and nothing validates their length. Count in UTF-16 units: an emoji counts as two. See Part.

Multi-building errors

Cannot find multibuilding: <name> and Cannot find building: <name>

When: chunk generation. code review

A city style's multibuildings selector, or a multi-building's grid, names something that does not exist. A missing namespace is almost always the cause, because a bare name means lostcities:<name>. See Namespaces. code review

If the message reads Cannot find multibuilding: null, the selector is empty

A literal null in the message means the mod asked the city style for a multi-building name and got nothing back, which happens when the merged multibuildings selector is empty. It surfaces once an area rolls at least one multi-building, so the count comes from the world style's multisettings. Either populate the selector or set multisettings.maximum to 0.

Invalid building for multibuilding!

When: chunk generation, on any chunk the mod decided to put a building on. code review

The name is misleading. This is the empty buildings selector error, and it has nothing to do with multi-buildings in the usual case. code review

The mod asks the city style for a random building name. When the merged buildings selector is empty, the weighted picker returns null, and the mod throws this rather than continuing. code review

Fix: give the city style at least one entry in selectors.buildings, or inherit from a style that has some. Remember that inheritance is additive, so writing "buildings": [] on a style that inherits citystyle_common still leaves you the parent's 8 entries. You only reach this error when the merged list is empty. See City Style.

Topleft building type is not set!

When: chunk generation, on a chunk that belongs to a multi-building but is not its top-left corner. code review

The mod looks up the top-left chunk's characteristics to find out which building this multi-chunk structure is, and that value came back null. In practice this follows from a multi-building whose grid does not match its dimx and dimz. code review

bound must be positive

When: chunk generation. This is an IllegalArgumentException from the JDK, with no message of the mod's own. code review

The random number generator throws it when a range is empty. There are three known causes, and none of them produces a helpful message. code review

Cause Fix code review
A multi-building's dimx or dimz exceeds the areasize it is placed with (multisettings.areasize defaults to 10, scattered.areasize to 8) Raise areasize or shrink the multi-building. See Multi-Building.
A Stuff Object whose maxcount is equal to or below its mincount maxcount must be strictly greater.
A Stuff Object whose maxheight is equal to or below its minheight The same rule.

Asset lookup errors

Can't find '<name>' in minecraft:root!

When: world load or chunk generation, depending on the asset type. code review

A name did not resolve. game test

The message does not tell you which kind of asset it was

The trailing part looks like it should name the registry, but the mod prints the root registry rather than lostcities:citystyles or lostcities:parts. The string is identical for every asset type, so it carries no information. To find out what the mod was looking up, read the stack trace. The frame below the lookup names the caller.

A missing namespace is by far the most common cause. A bare name resolves against lostcities:, so "mycity" looks for lostcities:mycity and finds nothing. A wrong file path is the second most common. Assets live at data/<namespace>/lostcities/<type>/<name>.json, with one lostcities segment, not two. game test

Error getting resource <name>!

When: the same situation, except that the underlying failure was an exception rather than a missing entry. The wrapped cause below it in the stack trace is the real message. game test

Invalid name given to minecraft:root getOrThrow!

When: the same lookup, when the name was null rather than wrong. Look for a missing key, not a misspelled one. game test

The usual cause is an empty bridges selector

A city style with "bridges": [] produces this on the first city chunk that has a building. The mod resolves the bridge part eagerly, alongside the door block and the stair part, and does not test bridgeChance first. Setting the chance to 0 does not protect an empty list.

Keep at least one entry in bridges and set bridgeChance to 0 if you do not want bridges. See City Style.

Streets that are absent, with a warning in the log

This is not a crash. A street part lookup warns and skips instead of throwing, so a bad street part name produces Cannot find '<name>' in minecraft:root! as a warning, and a chunk with no street layer. code review

Note the wording differs by one word between the two paths. The throwing path says Can't find, and the warning path says Cannot find. Highways, railways and monorails throw for the same mistake. See Streets, Highways, Rails and Monorails. code review

Configuration errors

Bad landscape type: <type>!

When: profile load, at startup. code review

A profile's landscapeType is not one of the six accepted values: default, floating, space, cavern, spheres, cavernspheres. Check the spelling and the case. game test

Unknown base profile '<name>'!

When: profile load. A profile, or a mod creating one through the API, inherits from a base profile that does not exist. code review

Bad value for 'highwayLevelFromCities'!

When: generation. The profile's highwayLevelFromCities is not 0, 1, 2 or 3. Nothing clamps the value, so any other number reaches the switch and throws. code review

On 7.5.0 and later the key also accepts 4, so only a value outside 0 to 4 throws there. See What changed in 7.5. code review

Bad range specification: <l1>,<l2>!

When: the mod parses a Condition or a building part reference with a malformed range. code review

range must be a string holding two integers separated by a comma, for example "range": "1,3". It throws for one number, for a non-number, and for a stray space such as "1, 3". game test

A third number does not throw

The mod reads only the first two pieces. "1,2,3" produces the range 1 to 2 and discards the 3, with no error and no log line. If your floors are wrong and you get no message, check for an extra number here.

Can't find a valid spawn position!

When: world creation. The world fails to create at all. code review

The profile's spawn settings cannot be satisfied. Setting any of spawnBiome, spawnCity, spawnSphere, spawnNotInBuilding, forceSpawnInBuilding, forceSpawnBuildings or forceSpawnParts replaces the vanilla spawn search rather than layering onto it. If the combination is impossible within spawnCheckAttempts chunks, world creation fails outright. code review

Cause Fix code review
A spawnCity or spawnSphere name with no matching Predefined asset Correct the name or remove the key.
Contradictory filters, such as spawnNotInBuilding with forceSpawnInBuilding Choose one.
A combination that is merely rare Raise spawnCheckAttempts and spawnCheckRadius.

Condition '<name>' did not return a valid mob!

When: chunk generation, while the mod places a spawner. code review

A palette entry's mob key names a Condition, and that condition matched nothing in this context. Add an unconditioned fallback entry to the condition's values, exactly as you would for building parts. game test

This error also corrects a common misconception. mob is not a mob ID. It is a condition name. See Palette. game test

Messages added in 7.5

Version 7.5.1 has 36 messages that 7.4.12 does not, and removes none of the older ones. Every one comes from the planned road system or the inter-city highway network, so none of them can appear on 7.4.12. They also appear on 8.4.1, 9.5.1 and 10.0.1, which carry the same system. code review

No 7.5.0 jar was checked, so these are attributed to the 7.5 line rather than to a specific patch release.

If you see one of these, your road settings are the cause, not your datapack. code review

Road settings rejected at config load

The mod validates the road keys against each other, not only against their own ranges. A value inside its own range still throws if it contradicts another key. code review

Message Keys involved code review
Primary road candidate spacing must be between 8 and 128 chunks primaryRoadSpacingX, primaryRoadSpacingZ
Road separation and edge distance must be between 2 and 32 chunks minimumRoadSeparation, minimumRoadEdgeDistance
Secondary road counts must be between 0 and 128 the four secondaryRoad*Count* keys
Secondary road minimum counts cannot exceed maximum counts secondaryRoadMinCountX against secondaryRoadMaxCountX, and the Z pair
tertiaryRoadMinLength cannot exceed tertiaryRoadMaxLength tertiaryRoadMinLength, tertiaryRoadMaxLength
Invalid tertiary road chance or length tertiaryRoadChance with the two length keys
Invalid primary road activation chance or forced interval primaryRoadOptionalChance, primaryRoadForceEvery
Invalid planned primary bridge chance or maximum length plannedPrimaryBridgeChance, plannedPrimaryBridgeMaxLength
highwayMinimumHubDistance cannot exceed highwayMaximumHubDistance the two hub distance keys
highwayHubSampleSpacing cannot exceed highwayPlanningCellSize highwayHubSampleSpacing, highwayPlanningCellSize

Road settings rejected when the planner is built

The same values are checked a second time, by the planner itself. These messages are worded differently from the ones above even when they guard the same key, so match on the exact text to tell which check failed. code review

Message Source code review
Invalid primary road activation settings Street planner
Invalid secondary road count range Street planner
Invalid tertiary road settings Street planner
Primary road candidate spacing must be at least 8 chunks Street planner
Road separation and edge distance must be at least 2 chunks Street planner
Highway planning-cell size must be between 32 and 512 chunks Highway planner
Highway hub sample spacing must be positive and no larger than the planning cell Highway planner
Highway hub minimum potential must be between 0 and 1 Highway planner
Highway hub search radius must be between 0 and 8 cells Highway planner
Highway minimum hub distance must not exceed the maximum Highway planner
Highway maximum hub distance must not exceed 4096 chunks Highway planner
Highway maximum connection degree must be between 1 and 8 Highway planner
Invalid highway route length or city penalty Highway planner
Invalid highway level mode or fixed network level Highway planner

The inter-city highway planner is unavailable in LEGACY mode

When: something asks for the highway planner while highwayGenerationMode is LEGACY. code review

The two modes are not interchangeable at runtime. Set highwayGenerationMode to INTERCITY_NETWORK_V1, or leave the caller alone. This is a separate key from streetGenerationMode: setting one to LEGACY does not set the other.

Logged warnings, not crashes

These two are logged and generation continues. They appear in logs/latest.log with the [lostcities/] prefix, and nowhere else. code review

Message Meaning code review
Unknown persisted street mode '<name>' for <dimension>; using LEGACY The world's saved street mode is not a name the mod recognises. It falls back to LEGACY, so the world generates with 7.4.12 street behaviour from then on.
Unknown persisted highway mode '<name>' for <dimension>; using LEGACY The same, for highways.

9.5.1 and 10.0.1 removed these two warnings

The saved data keys are unchanged, but neither version logs this message. On those versions an unrecognised saved mode produces no line at all. Do not read a silent log as proof that the mode loaded correctly.

Messages that indicate a mod bug

These carry no useful information for an author. code review

Message Where it comes from code review
Lost Cities generation context is not active Generation context, accessed outside a generation pass.
Cannot access Lost Cities world generation data without an overworld Saved data lookup.
Cannot access Lost Cities highway data without an overworld Highway saved data lookup.
No forced primary candidate found Street planner, choosing a forced corridor.
Highway connection endpoints must be distinct and canonical Highway graph construction.
X highway segment must have a constant Z coordinate Highway segment construction.
Z highway segment must have a constant X coordinate Highway segment construction.
Scattered buildings only support rotations Scattered placement, given a transform that is not a rotation.
Don't access this client-side! Server-only data reached from the client. Added in 8.4.1, not present in 7.5.1.

Errors that indicate a mod bug, not your content

These carry no useful information for an author. Plain JSON content that produces one is worth reporting upstream. code review

Message Where it comes from code review
Not possible! Street shape selection.
Error with rail! Railway generation.
This is really impossible! Railway layout.
This cannot happen: <n> Chunk writing.
Cannot happen! Transform and setup.
Staring interpolation twice Noise generation. The typo is the mod's.
Trying to sample interpolator outside the interpolation loop Noise generation.
Invalid SpawnData Spawner placement, when the mod fails to encode the spawner NBT it has just built.
Cannot find city style for chunk: <coord> Multi-building placement. Usually a world style with an empty citystyles list.
Missing buildings for scattered '<name>'! A Scattered asset with neither buildings nor multibuilding.
Could not find category '<name>'! The config screen asked for a settings category that does not exist.
Could not find value '<name>'! The config screen asked for a setting that does not exist.
Missing category: <name> Config registration, before any profile is read.

The last three come only from the in-game config screen and the mod's own startup. Editing a profile JSON by hand cannot produce them. code review

Nothing happens, and there is no error at all

This is the most common failure of all. The mod does not warn about content it never found. game test

Work through When nothing happens.