RubyVM::AbstractSyntaxTree.of(method) returns meaningless node if the method is defined in eval
RubyVM::AST.of(method) returns a meaningless node if the method is defined in eval.
p 'blah' eval <<~RUBY, binding, __FILE__, __LINE__ + 1 def foo end RUBY method = method(:foo) pp RubyVM::AbstractSyntaxTree.of(method) # => (STR@3:5-3:12 "def foo\n" + "end\n")
I expect the node of
foo method, or
nil. But it returns a
It becomes a big problem when
AST.of receives arbitrary methods.
Because we can't distinguish a method is defined in
eval or not.
It means we can't believe the returned value of
AST.of if the method may receive a method defined in
def do_something_for_each_method_ast(klass) klass.instance_methods(false).each do |m| ast = RubyVM::AbstractSyntaxTree.of(klass.instance_method(m)) next unless ast do_something ast end end class A eval <<~RUBY, binding, __FILE__, __LINE__ + 1 def foo end RUBY end do_something_for_each_method_ast A
In the example, I expect the
do_something method receives only node for a method definition,
but it may pass a wrong node if any method is defined in
Cause (I guess)¶
I guess the cause is misleading node number.
In and out of an
eval block uses different sequences of node number.
So if I specify
eval, the actual file and code in
eval may have the same node number.
p 'blah' # Node number for 'blah' is 1, file name is "test.rb" eval <<~RUBY, binding, __FILE__, __LINE__ + 1 def foo # Node number for `def` is also 1, file name is also "test.rb" end RUBY method = method(:foo) # It finds a node from node number 1 by reading "test.rb", so it get the str node. pp RubyVM::AbstractSyntaxTree.of(method) # => (STR@3:5-3:12 "def foo\n" + "end\n")
Updated by jeremyevans0 (Jeremy Evans) 5 months ago
I'm not sure if this is a bug, but it does seem like a fundamental and significant limitation with the design of RubyVM::AbstractSyntaxTree.of. RubyVM::AbstractSyntaxTree.of reparses the file the method is defined in and cannot handle any cases where
eval or similar are used. You'll get a node completely different from what you would expect. Here's another example:
eval DATA.read, binding, __FILE__, 14 method = method(:foo) pp RubyVM::AbstractSyntaxTree.of(method) __END__ def foo end
Because it reparses the file, you'll also get the wrong result if the file is modified:
def bar end File.write(__FILE__, File.read(__FILE__).gsub('def bar', "def foo\nbar")) method = method(:bar) pp RubyVM::AbstractSyntaxTree.of(method)
(SCOPE@1:0-3:3 tbl:  args: (ARGS@1:7-1:7 pre_num: 0 pre_init: nil opt: nil first_post: nil post_num: 0 post_init: nil rest: nil kw: nil kwrest: nil block: nil) body: (VCALL@2:0-2:3 :bar))
And if the interpreter can no longer access the file (chroot, file deletion, permission change, or other file system access limiting), you get an error.
I can't think of a way to fix this without all iseq methods holding a reference to the string used to parse them, and having RubyVM::AbstractSyntaxTree.of work off that string. I'm not sure how much extra memory use that would cause, or if such an approach is considered acceptable.