NB : note that MC-140973, MC-140759, MC-140975 and MC-143112 are very similar issues. They are all due to mistakes made when creating village's structures or arranging those in files where they shouldn't be.

The bug

Villagers aren't spawning in some houses (actually in a lot of them). This can lead to some issues, the first being that some villages don't contain any villagers ! More generally, villages will have a really small amount of villagers in comparison with the number of houses. An other issue is that Iron Golems won't spawn naturally, 99% of the time. This is also due to the doors requirement (you need more than 21 in a village, and naturally generated ones don't have such a number), which is too high and should be reduced.

Example of an empty village in 19w07a (this seed isn't working anymore since 19w08a because village generation changed, but the issue remains unfixed) :

Seed : 5419467522569981067

Coordinates : -2550 ~ 2150

No villager spawned in this village.

 

 

This can be explained by the way villagers are generated now.

A villager will now spawn if there is a Jigsaw block in a house whose role is to spawn a villager. These Jigsaw blocks aren't generated in every house.

This is how they look like :

 
 

Here is a list of houses that don't have this key Jigsaw block.

Plains Village :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\plains\houses

Houses that doesn't generate Jigsaw villager :

• plains_armorer_house_1
• plains_butcher_shop_1
• plains_butcher_shop_2
• plains_cartographer_1
• plains_fisher_cottage_1
• plains_fletcher_house_1
• plains_library_1
• plains_library_2
• plains_masons_house_1
• plains_shepherds_house_1
• plains_tannery_1
• plains_temple_3
• plains_temple_4
• plains_tool_smith_1
• plains_weaponsmith_1

 

Plains Village (zombie) :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\plains\zombie\houses

Houses that don't generate Jigsaw zombie villager :

• plains_butcher_shop_2
• plains_fletcher_house_1
• plains_shepherds_house_1

 

Savanna Village :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\savanna\houses

Houses that don't generate Jigsaw villager :

• savanna_armorer_1
• savanna_butchers_shop_1
• savanna_butchers_shop_2
• savanna_cartographer_1
• savanna_fisher_cottage_1
• savanna_fletcher_house_1
• savanna_library_1
• savanna_mason_1
• savanna_shepherd_1
• savanna_tannery_1
• savanna_temple_1
• savanna_temple_2
• savanna_tool_smith_1
• savanna_weaponsmith_1
• savanna_weaponsmith_2

 

Snowy Village :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\snowy\houses

Houses that don't generate Jigsaw villager :

• snowy_armorer_house_1
• snowy_armorer_house_2
• snowy_butchers_shop ** (duplicated file. Relates to MC-143112)
• snowy_butchers_shop_1
• snowy_butchers_shop_2
• snowy_cartographer_house_1
• snowy_fisher_cottage
• snowy_fletcher_house_1
• snowy_library_1
• snowy_masons_house_1
• snowy_masons_house_2
• snowy_shepherds_house_1
• snowy_small_house_8
• snowy_tannery_1
• snowy_temple_1
• snowy_tool_smith_1
• snowy_weapon_smith_1

 

Snowy Village (zombie) :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\snowy\zombie\houses

Houses that don't generate Jigsaw zombie villager :

• snowy_small_house_8

 

Desert Village :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\desert\houses

Houses that don't generate Jigsaw villager :

• desert_armorer_1
• desert_butcher_shop_1
• desert_cartographer_house_1
• desert_fisher_1
• desert_fletcher_house_1
• desert_library_1
• desert_mason_1
• desert_shepherd_house_1
• desert_tannery_1 (+ generates weirdly, blocks are missing under the house. See screenshot)

• desert_temple_1
• desert_temple_2
• desert_tool_smith_1
• desert_weaponsmith_1

 

Taiga Village :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\taiga\houses

Houses that don't generate Jigsaw villager :

• taiga_armorer_2
• taiga_armorer_house_1
• taiga_butcher_shop_1
• taiga_cartographer_house_1
• taiga_fisher_cottage_1 (+ generates weirdly, water is generated in the house instead of under trapdoors. See screenshot. Relates to MC-141034)

• taiga_fletcher_house_1
• taiga_library_1
• taiga_masons_house_1
• taiga_medium_house_3
• taiga_medium_house_4
• taiga_sheperds_house_1 (duplicated file. Relates to MC-143112)
• taiga_shepherds_house_1
• taiga_tannery_1
• taiga_temple_1
• taiga_tool_smith_1
• taiga_weapon_smith_1 (duplicated file. Relates to MC-143112)
• taiga_weaponsmith_1
• taiga_weaponsmith_2

 

Taiga Village (zombie) :

Location of the file :

.minecraft\versions\<version>\<version>.jar\data\minecraft\structures\village\taiga\zombie\houses

Houses that don't generate Jigsaw zombie villager :

• taiga_cartographer_house_1
• taiga_fisher_cottage_1
• taiga_library_1
• taiga_medium_house_3
• taiga_medium_house_4
• taiga_shepherds_house_1
• taiga_temple_1
• taiga_tool_smith_1
• taiga_weaponsmith_2

 

It seems like even if the jigsaw block is generated, the villager doesn't spawn sometimes. Example : a Jigsaw block is generated in all plains small houses but in the given seed there isn't any villager despite that a small house was generated in the village. I don't really know what causes this issue, and I maybe should create an other bug report for that.

How to fix the bug :

As you can see, most of affected houses are assigned to a certain profession. I suggest that you could add a Jigsaw Block to each of them, that spawns the villager that is supposed to work in the house, which avoids the problem to find a library house without any librarian villager in the village for example (the best could be that these villagers would spend the night in their house, like if they were assigned to it ; it is only a suggestion). An other problem is that farms and animal pens are also considered as "house". It could lead to strange villages that only have farms and pens, without any house (and therefore without any villagers). In order to fix entirely the bug, farms and animal pens need to be moved in an other file. Some decorations are also in house files, such as plains_accessory_1 (in plain villages). They need to be moved too. This last point relates to MC-140975.