From: Colin Kelley <colindkelley@...>
Date: 2015-11-29T15:24:33-08:00
Subject: [ruby-core:71738] behavior of Array#dig when passed a non-numeric	index?

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Hello,

I am working on this gem to provide backward-compatibility of the new `dig`
method in `Hash` and `Array`.

    https://rubygems.org/gems/ruby_dig

(See the accompanying blog post for more info.
http://development.invoca.com/ruby_dig-gem-adds-hash-dig-and-array-dig-from-ruby-2-3-to-earlier-versions/
)

But I can't tell from the documentation or tests in the original commit


https://github.com/ruby/ruby/commit/29862685c0acf3a40c6b1f9e8780cbbd86cba658

what is supposed to happen if Array#dig is passed a non-numeric index. For
example:

    ['zero', 'one', 'two'].dig(:first)

It seems like the C code is just calling the `[]` operator, in which case
it would raise this exception:

    TypeError: no implicit conversion of Symbol into Integer
But it definitely seems like the spirit of `dig` that `nil` should be
returned if the expected structure isn't there.  I believe the most typical
use case for `dig` is to dig through a JSON hash and either find the result
we expected, or get `nil`.  Wouldn't it defeat the purpose of `dig` if we
had to wrap it in a `rescue`?

Can we clarify the desired behavior, then update the documentation and
tests to reflect that?

-Colin

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<div dir=3D"ltr">Hello,<div><br></div><div>I am working on this gem to prov=
ide backward-compatibility of the new `dig` method in `Hash` and `Array`.=
=C2=A0</div><div><br></div><div>=C2=A0 =C2=A0 <a href=3D"https://rubygems.o=
rg/gems/ruby_dig">https://rubygems.org/gems/ruby_dig</a><br></div><div><br>=
</div><div>(See the accompanying blog post for more info. =C2=A0<a href=3D"=
http://development.invoca.com/ruby_dig-gem-adds-hash-dig-and-array-dig-from=
-ruby-2-3-to-earlier-versions/">http://development.invoca.com/ruby_dig-gem-=
adds-hash-dig-and-array-dig-from-ruby-2-3-to-earlier-versions/</a> )</div><=
div><br></div><div>But I can&#39;t tell from the documentation or tests in =
the original commit</div><div><br></div><div>=C2=A0 =C2=A0 <a href=3D"https=
://github.com/ruby/ruby/commit/29862685c0acf3a40c6b1f9e8780cbbd86cba658">ht=
tps://github.com/ruby/ruby/commit/29862685c0acf3a40c6b1f9e8780cbbd86cba658<=
/a><br></div><div><br></div><div>what is supposed to happen if Array#dig is=
 passed a non-numeric index. For example:</div><div><br></div><div><font fa=
ce=3D"monospace, monospace">=C2=A0 =C2=A0 [&#39;zero&#39;, &#39;one&#39;, &=
#39;two&#39;].dig(:first)</font></div><div><br></div><div>It seems like the=
 C code is just calling the `[]` operator, in which case it would raise thi=
s exception:</div><div>







<p class=3D""><span class=3D""><font face=3D"monospace, monospace">=C2=A0 =
=C2=A0 TypeError: no implicit conversion of Symbol into Integer</font></spa=
n></p></div><div>But it definitely seems like the spirit of `dig` that `nil=
` should be returned if the expected structure isn&#39;t there.=C2=A0 I bel=
ieve the most typical use case for `dig` is to dig through a JSON hash and =
either find the result we expected, or get `nil`.=C2=A0 Wouldn&#39;t it def=
eat the purpose of `dig` if we had to wrap it in a `rescue`?</div><div><br>=
</div><div>Can we clarify the desired behavior, then update the documentati=
on and tests to reflect that?</div><div><br></div><div>-Colin</div><div><br=
></div></div>

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