View Source Alembic.Parser.Expression (alembic v0.1.0)

Parses the raw string content of a Liquid expression — everything that can appear inside {{ ... }} output tags and {% if ... %} / {% for ... in ... %} conditions — into an Alembic.AST.expr() node.

Grammar (see docs/grammar.md):

expr             = or_expr ;
or_expr          = and_expr , { "or" , and_expr } ;
and_expr         = not_expr , { "and" , not_expr } ;
not_expr         = [ "not" ] , comparison ;
comparison       = filtered_primary , [ compare_op , filtered_primary ] ;
filtered_primary = primary , { filter } ;
primary          = variable | literal ;
filter           = "|" , IDENT , [ ":" , expr , { "," , expr } ] ;

Filters bind tighter than comparison and logical operators — this lets a bare "name | upcase" parse on its own (used for output tags) while still allowing filtered operands inside a condition, e.g. x | size > 0.

Summary

Types

reason()

Functions

parse(source)

Parses the raw string content of an output tag or a tag condition into an Alembic.AST.expr().

Types

reason()

@type reason() ::
  :empty_expression
  | :unterminated_string
  | :missing_filter_name
  | {:unknown_operator, String.t()}
  | {:unexpected_token, term()}

Functions

parse(source)

@spec parse(String.t()) :: {:ok, Alembic.AST.expr()} | {:error, reason()}

Parses the raw string content of an output tag or a tag condition into an Alembic.AST.expr().

Examples

iex> Alembic.Parser.Expression.parse("user.name")
{:ok, {:variable, ["user", "name"]}}

iex> Alembic.Parser.Expression.parse("name | upcase")
{:ok, {:filter_chain, {:variable, ["name"]}, [{:filter, "upcase", []}]}}

iex> Alembic.Parser.Expression.parse("x > 0 and not skip")
{:ok,
 {:logical, :and, {:compare, :gt, {:variable, ["x"]}, {:literal, 0}},
  {:not, {:variable, ["skip"]}}}}