Allow explode and implode definitions to specify object or array shape

[kjellmorten]

Context

explode can represent both objects and arrays as arrays of { key, value } entries. implode currently infers the source shape from the key types:

• numeric keys produce an array
• string keys produce an object

This inference cannot distinguish an empty object from an empty array because both explode to []. Consequently, an empty-array round trip currently behaves like this:

explode([]) // []
implode([]) // {}

Suggestion

Allow the transformer definition to specify the intended shape explicitly, for example:

{ $transform: "explode", type: "array" }
{ $transform: "explode", type: "object" }

The exact property name is open for discussion. When provided, it could:

• resolve the empty-input ambiguity in the inverse direction
• optionally validate that entry keys are compatible with the declared shape
• make the transformation contract clearer for integrations with a known schema

Without an explicit shape, the current key-based inference could remain the default for compatibility.

Acceptance considerations

• Add forward and reverse tests for empty objects and empty arrays.
• Document behavior when the declared shape conflicts with entry key types.
• Decide whether the option belongs to both explode and implode, or whether direction handling makes one shared option sufficient.