Parser for A2UI expression templates — the ${…} interpolation language used by formatString and by dynamic string values.

parse/1 turns a template into a list of parts:

• literal text (a string),
• a literal value from inside an interpolation: a string ('x', "x"), a number (42, -1.5, 1e5) or a boolean,
• a data binding %{"path" => path} (${/user/name}, ${count}),
• a function call %{"call" => name, "args" => %{…}, "returnType" => "any"} (${add(a: 1, b: /x)}); arguments are themselves expressions. A system function is named with @ and must be called: ${@index(offset: 1)}.

\${ is an escaped marker and yields the literal ${. null yields nothing. Whitespace inside an interpolation is ignored.

Limits (shared by every reference engine so they accept the same inputs): templates up to 10 000 characters, 1 000 parts, nesting depth 100.

Errors are {:error, %A2UICore.Error{category: :expression}}: unclosed interpolation, a missing : or ) in a call, trailing characters, an invalid or out-of-range number literal, and exceeded limits.

iex> A2UICore.Expression.parse("Hello, ${/user/name}!")
{:ok, ["Hello, ", %{"path" => "/user/name"}, "!"]}
iex> A2UICore.Expression.parse("${add(a: 1, b: 2)}")
{:ok, [%{"call" => "add", "args" => %{"a" => 1, "b" => 2}, "returnType" => "any"}]}
iex> {:error, error} = A2UICore.Expression.parse("${oops")
iex> error.message
"Unclosed interpolation: missing '}'"