Bug #13337: Eval and Later Defined Local Variables

• Status: Closed
• Priority: Normal
• Assignee: -
• Target version: -
• ruby -v: 2.4.0
• Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN

[faraz (Faraz Yashar)]

I've noticed the following behavior with eval:

def example
  eval("foo") # => nil, but would expect a NameError
  eval("bar") # => NameError
  foo = 1
end

I'm assuming this behavior is expected, since "eval" executes in the context of the existing YARV instructions and local table, but I'm not certain since I haven't seen this behavior documented anywhere.

[ko1 (Koichi Sasada)]

This is specification.

(1) parse example method and define foo.
(2) In eval method, compile given string ("foo") and defined foo was used (without any problem).

So it is documentation issue.
Can anyone write about it?

[jeremyevans0 (Jeremy Evans)]

• File doc-eval-local-var.patch doc-eval-local-var.patch added

ko1 (Koichi Sasada) wrote:

This is specification.

(1) parse example method and define foo.
(2) In eval method, compile given string ("foo") and defined foo was used (without any problem).

So it is documentation issue.
Can anyone write about it?

Attached is a documentation patch. However, a committer with more knowledge of the internals should probably check to see if it is technically accurate.

[chrisseaton (Chris Seaton)]

This is as specified here

https://github.com/ruby/spec/blob/db74bf3313b4d49650417ba91b4e2d67cc253dc5/core/kernel/eval_spec.rb#L31-L68

[nobu (Nobuyoshi Nakada)]

jeremyevans0 (Jeremy Evans) wrote:

Attached is a documentation patch.

Seems fine.

A question:

However, local variables set inside the call to +eval+ will not be reflected in the surrounding scope.

Isn't "set" vague a little, between "defined" an "assigned"?

• Status changed from Open to Closed

Applied in changeset git|0bd5f846df2f6268f653773e0cd4a20e2a944646.

---

Document local variable interactions with eval

Fixes [Bug #13337]

[nobu (Nobuyoshi Nakada)]

"local variables assigned inside the call to +eval+" sounds like a just assignment to a local variable defined outside, doesn't it?

[jeremyevans0 (Jeremy Evans)]

nobu (Nobuyoshi Nakada) wrote:

"local variables assigned inside the call to +eval+" sounds like a just assignment to a local variable defined outside, doesn't it?

It could definitely be interpreted that way. I'll reword it to make it more clear. Thanks!