mandatory.md

The stuff in the code_style.md document should be followed, but it is ultimately just about the readability of the source code. The following is really important though. If these guidelines are not followed, it can cause massive problems - and not just now, but also years in the future.

EnumProperty

Always add an index for each element. If the index is missing, we can not reorder elements later and we can not rename identifiers without breaking old .blend files.

Wrong:

items = [
    ("first_item", "First Item", "This is the first item"),
    ("second_item", "Second Item", "This is the second item"),
]

Correct:

items = [
    ("first_item", "First Item", "This is the first item", 0),
    ("second_item", "Second Item", "This is the second item", 1),
]

(note the 0 and 1 after the descriptions)