[dev-branch] NullReferenceException in GenStep Causes Desync When Creating New Faction (Mechanitor Scenario) #547
Description
Occurred in: BETA 0.10.6 for RW 1.5.4409
Label: dev-branch, 1.5, multifaction
Bug:
When a client starts a new faction with the mechanitor scenario, an error occurs during map generation, followed by a desync once the game is unpaused.
Steps to Reproduce
Mods: Prepatcher, Harmony, Biotech, Ideology, Royalty, Multiplayer
- Host a multiplayer game.
- Join with another instance as client.
- As the client, start a new faction using the mechanitor scenario.
- During map generation, observe the following error: Error in GenStep: System.NullReferenceException: Object reference not set to an instance of an object
- Unpause the game - a desync occurs.
Technical Details / Cause
- The issue occurs because TickManager.Pause is called, and the Multiplayer Harmony Postfix patch references Game.currentMap, which is null at this point in map generation.
- A guard for currentMap == null was added in Improved starting experience for multifaction #508 but later reverted (adc9d8b#diff-e2d1935affa8fc6df58e22fb262dd657d4774930103d508fd4b70e1f446868b9L150) due to uncertainty about its purpose - both in code review (noted by @SokyranTheDragon) and because I had forgotten the reason myself after writing it 6 months earlier. The fix should be more explicit and self-explanatory, rather than relying on a simple guard clause without clear context.