From: xkernigh@...
Date: 2019-10-24T02:37:37+00:00
Subject: [ruby-core:95525] [Ruby master Bug#16251] Evaluation in binding differs from ruby execution

Issue #16251 has been updated by kernigh (George Koehler).


This is a simpler example of the behavior:

```
$ ruby -e 'p x; x = 6'
Traceback (most recent call last):
-e:1:in `<main>': undefined local variable or method `x' for main:Object (NameError)
$ ruby -e 'p eval("x"); x = 6'
nil
$ ruby -e 'p binding.eval("x"); x = 6'
nil
```

A plain `x` raises NameError, but an `eval("x")` or `binding.eval("x")` fetches nil from the local variable x.  I expect this behavior, because Ruby parses a script before running it:

1. Ruby parses `x = 6` and adds x to the binding.
2. Ruby runs `eval("x")` with x in the binding.
3. Ruby runs `x = 6` and changes the value of x from nil to 6.

Binding#local_variables reveals the local variable named x:

```
$ ruby -e 'p binding.eval("x"); x = 2'
[:x]
```

Because x exists, `binding.eval("x")` has the expected behavior, so there is no bug.

----------------------------------------
Bug #16251: Evaluation in binding differs from ruby execution
https://bugs.ruby-lang.org/issues/16251#change-82300

* Author: teslur (Tetsushi FUKABORI)
* Status: Closed
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.2p47 (2019-03-13 revision 67232) [x86_64-darwin18]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
In specific situation, I found that result of string evaluation in Binding returns different from ruby execution result.

In following sample code, ruby evaluates `method_or_local_var` as method call and returns `"method"`.
However, `binding.eval` evaluates `method_or_local_var` as local variable and returns `nil`.

Here is sample code.
```
def method_or_local_var
  'method'
end

if true
  puts "execute method_or_local_var:"
  p method_or_local_var #=> "method"

  puts "execute method_or_local_var by bind.eval('method_or_local_var'):"
  p binding.eval('method_or_local_var') #=> nil
else
  method_or_local_var = 'local variable'
end
```

and here is results of execute sample code.
```
��� ruby sample_code.rb
execute method_or_local_var:
"method"
execute method_or_local_var by bind.eval('method_or_local_var'):
nil
```

I expect evaluation result of `method_or_local_var` in binding to be method, and returns `"method"`.
Is this the expected behavior?



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>