ExAST.Pattern (ExAST v0.3.0)

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AST pattern matching with captures.

Patterns are valid Elixir syntax where:

  • Bare variables (name, expr) capture the matched AST node
  • _ and _name are wildcards (match anything, don't capture)
  • Structs and maps match partially (only specified keys must be present)
  • Pipes are normalized (data |> Enum.map(f) matches Enum.map(data, f))
  • Multi-statement patterns match contiguous sequences in blocks

Repeated variable names require the same value at every position.

Summary

Types

captures()

Functions

match(node, pattern_string)

Matches a Sourceror AST node against a pattern string.

match_ast(node, pattern_ast)

Matches a Sourceror AST node against an already-parsed pattern AST.

match_sequences(nodes, pattern_asts)

Finds all contiguous subsequences of nodes matching pattern_asts.

multi_node?(pattern_string)

Returns true if the pattern string contains multiple statements (separated by ; or newlines), enabling sequential matching.

pattern_nodes(pattern_string)

Returns the individual pattern ASTs from a multi-node pattern string.

substitute(template_ast, captures)

Substitutes captured values into a replacement template AST.

Types

captures()

@type captures() :: %{required(atom()) => term()}

Functions

match(node, pattern_string)

@spec match(Macro.t(), String.t()) :: {:ok, captures()} | :error

Matches a Sourceror AST node against a pattern string.

Returns {:ok, captures} on match, :error otherwise.

match_ast(node, pattern_ast)

@spec match_ast(Macro.t(), Macro.t()) :: {:ok, captures()} | :error

Matches a Sourceror AST node against an already-parsed pattern AST.

match_sequences(nodes, pattern_asts)

@spec match_sequences([Macro.t()], [Macro.t()]) :: [{captures(), Range.t()}]

Finds all contiguous subsequences of nodes matching pattern_asts.

Returns a list of {captures, start_index..end_index} tuples. Captures are accumulated across all matched nodes and must be consistent.

multi_node?(pattern_string)

@spec multi_node?(String.t()) :: boolean()

Returns true if the pattern string contains multiple statements (separated by ; or newlines), enabling sequential matching.

pattern_nodes(pattern_string)

@spec pattern_nodes(String.t()) :: [Macro.t()]

Returns the individual pattern ASTs from a multi-node pattern string.

substitute(template_ast, captures)

@spec substitute(Macro.t(), captures()) :: Macro.t()

Substitutes captured values into a replacement template AST.

Variables in the template that match capture names are replaced with the captured AST nodes.