roboto.templating.substitution

A VariableResolver backed by a flat name -> value mapping.

Values are coerced to str on access; a missing key or a None value resolves to None (leaving the placeholder unexpanded).

MappingResolver.resolve()

Recognizes {{name}} placeholders. Names start with a letter or underscore; dots are allowed so dotted names ({{dataset.id}}, {{action.name}}) work as a namespace convention for entity-bound expansion by a VariableResolver. The engine treats the full dotted string as one opaque key — the resolver decides what, if anything, it expands to.

Mirrors PLACEHOLDER_RE so every declared variable name is referenceable by {{name}}.

Bases: Protocol

Decides what each {{name}} placeholder expands to during substitution.

Implementations bind placeholders to a source of values — a flat mapping for agent launch, or a lazily-hydrated event namespace for triggers — keeping the substitution engine itself agnostic to where values come from.

VariableResolver.resolve()

Return every {{name}} placeholder found in the string leaves of node.

node is the JSON form of a template (nested dicts, lists, scalars). Only string values are scanned; placeholder syntax in dict keys is rejected so a templated key can’t silently collapse two entries into one.

Return a copy of node with each {{name}} in a string leaf expanded via resolver.

Embedded and repeated placeholders within one string are supported. A name the resolver returns None for is left as the literal {{name}}; callers that require full resolution validate the placeholder set up front with collect_placeholders().