Class: DynamicLocals::ASTRewriter

Inherits:
Object
  • Object
show all
Defined in:
lib/dynamic_locals/ast_rewriter.rb

Defined Under Namespace

Classes: Replacement

Constant Summary collapse

WRAPPER_NAME =

The source we translate is a method body: it may legally use constructs that are only valid inside a method -- yield, a top-level return, and an implicit begin/rescue (raise; rescue; ...). Parsing it as a standalone program rejects those, so we parse it wrapped in a method definition and then map node offsets back onto the original (unwrapped) source.

"__dynamic_locals_parse_wrapper__"
WRAPPER_PREFIX = 
"def #{WRAPPER_NAME}\n"
WRAPPER_SUFFIX = 
"\nend"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(source) ⇒ ASTRewriter

Returns a new instance of ASTRewriter.

Raises:

  • (SyntaxError) 


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# File 'lib/dynamic_locals/ast_rewriter.rb', line 14

def initialize(source)
  @original_src = source.dup.freeze

  result, prefix = parse_with_locals([])
  errors = result.errors.reject { |error| error.type == :no_local_variable }
  raise SyntaxError, errors.map(&:message).join("\n") if errors.any?

  # A pin such as `^foo` reports :no_local_variable when `foo` will only be
  # supplied dynamically. Reparse with those names declared on the wrapper
  # method; pins in blocks then resolve naturally, while a pin beyond a real
  # scope boundary (a nested def/class/module body) remains a syntax error.
  implicit_locals = result.errors.filter_map do |error|
    error.location.slice.to_sym if error.type == :no_local_variable
  end.uniq
  result, prefix = parse_with_locals(implicit_locals) if implicit_locals.any?
  raise SyntaxError, result.errors.map(&:message).join("\n") unless result.success?

  @offset = prefix.bytesize
  @def_node = result.value.statements.body.first
  @replacements = []
end

Instance Attribute Details

#original_src ⇒ Object (readonly)

Returns the value of attribute original_src.



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# File 'lib/dynamic_locals/ast_rewriter.rb', line 38

def original_src
  @original_src
end

Instance Method Details

#ast ⇒ Object

The method body scope: a StatementsNode, a BeginNode (when the body has a rescue/else/ensure), or nil when the body is empty.



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# File 'lib/dynamic_locals/ast_rewriter.rb', line 42

def ast
  @def_node.body
end

#insert_after(node, src) ⇒ Object

Raises:

  • (TypeError) 


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# File 'lib/dynamic_locals/ast_rewriter.rb', line 74

def insert_after(node, src)
  raise TypeError unless Prism::Node === node

  insert_at(node.location.end_offset, src)
end

#insert_at(wrapped_offset, src) ⇒ Object

Offsets are relative to the wrapped source, as in Prism locations.



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# File 'lib/dynamic_locals/ast_rewriter.rb', line 81

def insert_at(wrapped_offset, src)
  pos = wrapped_offset - @offset
  @replacements << Replacement.new(pos...pos, src)
end

#insert_before(node, src) ⇒ Object

Raises:

  • (TypeError) 


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# File 'lib/dynamic_locals/ast_rewriter.rb', line 68

def insert_before(node, src)
  raise TypeError unless Prism::Node === node

  insert_at(node.location.start_offset, src)
end

#locals ⇒ Object

The method-level local table Ruby derives from the body.



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# File 'lib/dynamic_locals/ast_rewriter.rb', line 47

def locals
  @def_node.locals
end

#modified_src ⇒ Object 



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# File 'lib/dynamic_locals/ast_rewriter.rb', line 51

def modified_src
  # Apply right-to-left so earlier ranges stay valid. Ties are broken so
  # that a zero-width insertion at an offset is applied before a
  # replacement ending there (keeping the insertion outside the replaced
  # text), and same-position insertions land in registration order.
  rewrites =
    @replacements.each_with_index.sort_by do |replacement, index|
      [replacement.range.end, replacement.range.begin, index]
    end.reverse

  src = original_src.b
  rewrites.each do |replacement, _|
    src[replacement.range] = replacement.src.b
  end
  src.force_encoding(original_src.encoding)
end

#replace(node, src) ⇒ Object

Raises:

  • (TypeError) 


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# File 'lib/dynamic_locals/ast_rewriter.rb', line 90

def replace(node, src)
  raise TypeError unless Prism::Node === node

  range = range_from(node)
  @replacements << Replacement.new(range, src)
end

#replace_offsets(wrapped_start, wrapped_end, src) ⇒ Object 



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# File 'lib/dynamic_locals/ast_rewriter.rb', line 86

def replace_offsets(wrapped_start, wrapped_end, src)
  @replacements << Replacement.new((wrapped_start - @offset)...(wrapped_end - @offset), src)
end