Inherited properties in TOML

explicit.toml

[thing]
name = "demo"

[thing.version_a]
items = ['base1', 'base2', 'first1', 'first2']

[thing.version_b]
items = ['base1', 'base2', 'second1', 'second2']

implicit.toml

[thing]
name = "demo"
items = ['base1', 'base2']

[thing.version_a]
items = ['first1', 'first2']

[thing.version_b]
items = ['second1', 'second2']

inherit.toml

[thing]
name = "demo"
items = ['base1', 'base2']

[thing.version_a]
items = ['+', 'first1', 'first2']

[thing.version_b]
items = ['+', 'second1', 'second2']

[thing.version_c]
items = ['third1', 'third2']

separate.toml

[thing]
name = "demo"
items = ['base1', 'base2']

[thing.version_a]
sub_items = ['first1', 'first2']

[thing.version_b]
sub_items = ['second1', 'second2']

I wouldn't expect the inherit clause to lead to merged lists, because "inherit" sounds so all-or-nothing. "+" is more intuitive that way. Maybe this is just a naming thing though – if you don't intend to use it for primitives, "merge_with_parent" or something like that could work.

What about separate extend vs inherit directives?

What about separate extend vs inherit directives?

“Extend” would do the job!