TOML Arrays and JSON Arrays

TOML arrays map directly to JSON arrays, but with one significant restriction: TOML requires all elements in an array to be of the same type. This is a deliberate design choice that makes TOML configurations more predictable.

Basic TOML arrays:

ports = [8001, 8002, 8003]
hosts = ["alpha", "beta", "gamma"]
enabled = [true, false, true]

Converts to JSON:

{
  "ports": [8001, 8002, 8003],
  "hosts": ["alpha", "beta", "gamma"],
  "enabled": [true, false, true]
}

Multiline arrays (for readability):

contributors = [
  "Alice",
  "Bob",
  "Charlie",
]

TOML allows trailing commas in multiline arrays, which JSON does not. The converter strips trailing commas when producing JSON.

Nested arrays:

data = [[1, 2], [3, 4, 5]]

Converts to: {"data": [[1, 2], [3, 4, 5]]}

Nested arrays are valid as long as each sub-array is homogeneous within itself.

The type restriction:

In TOML, this is invalid:

# ERROR: mixed types in array
mixed = [1, "two", true]

JSON happily accepts mixed-type arrays, but TOML does not. When converting JSON to TOML, mixed-type arrays must be restructured -- for example, by converting all elements to strings or splitting into separate typed arrays.

Arrays of inline tables:

points = [{x = 1, y = 2}, {x = 3, y = 4}]

Converts to:

{
  "points": [{"x": 1, "y": 2}, {"x": 3, "y": 4}]
}

This is valid because each element is an inline table (object) with the same structure.