Bottom / Error

Specifying duplicate fields with conflicting values results in an error or bottom. Bottom is a special value in CUE, denoted _|_, that indicates an error such as conflicting values. Any error in CUE results in _|_. Logically all errors are equal, although errors may be associated with metadata such as an error message.

Note that an error is different from null: null is a valid value, whereas _|_ is not.

a: 4
a: 5

l: [ 1, 2 ]
l: [ 1, 3 ]

list: [0, 1, 2]
val: list[3]

a: _|_ // a: conflicting values 5 and 4
l: [1, _|_, // l.1: conflicting values 3 and 2
]
list: [0, 1, 2]
val: _|_ // val: index out of range [3] with length 3