From: ruby-core@...
Date: 2015-12-12T21:16:21+00:00
Subject: [ruby-core:72086] [Ruby trunk - Bug #11762] Array#dig can raise TypeError: no implicit conversion of Symbol/String into Integer

Issue #11762 has been updated by Marc-Andre Lafortune.


Yukihiro Matsumoto wrote:
> Hmm,
> 
> `{a: 'hello'}.dig(:a, :b)` should raise TypeError since a string do not have method `dig`.

Thanks Matz

I don't understand why it's would be a `TypeError`. I thought it would be a `NoMethodError` (or alternatively an `ArgumentError`, as reducing the number of arguments could make that error disappear).

My understanding was that a `TypeError` occurs iff an argument of an unexpected type occurs, but the error won't go away by changing the type of any argument.

Are you sure that `TypeError` is the best error to raise in this case?

Thanks

----------------------------------------
Bug #11762: Array#dig can raise TypeError: no implicit conversion of Symbol/String into Integer
https://bugs.ruby-lang.org/issues/11762#change-55499

* Author: Colin Kelley
* Status: Closed
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* ruby -v: 2.3.0-preview2
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
If you try to `dig` in an Array using a symbol or string, a `TypeError` exception will be raised:

irb> ['zero', 'one', 'two'].dig(:first)
TypeError: no implicit conversion of Symbol into Integer
    from (irb):1:in `dig'
    from (irb):1

I think it should return `nil` in this case.  The most typical use case for `dig` is to dig through parsed JSON and either find the result we expected or else `nil`.  Wouldn't it defeat the purpose of `dig` if we had to wrap calls to it in a `rescue` to handle the case that an Array was present where we expected a Hash?

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

---Files--------------------------------
11762.patch (3.19 KB)


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