# Weird problem with validating sum types from JSON

**URL:** <https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562>\
**Category:** dry-validation\
**Created:** [November 24, 2022, 10:11am UTC](https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562 "2022-11-24T10:11:52Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![rickenharp](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.dry-rb.org/rickenharp/32/12_2.png) [@rickenharp](https://discourse.dry-rb.org/u/rickenharp)\
**Post date:** [November 24, 2022, 10:11am UTC](https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562/1 "2022-11-24T10:11:52Z")

</div>

I’m slowly adding validations to a legacy ruby project. And that went mostly quite well, except for one piece of external data we are ingesting. I’ve narrowed the problem part down to this:

```json
{
  "response": [
    {
      "type": "DataSegment",
      "data": "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",
      "length": 884
    },
    {
      "type": "SnipSegment",
      "length": 394
    },
    {
      "type": "HighlightSegment",
      "data": "PHNjcmlwdCB0eXBlPSJ0ZXh0L2phdmFzY3JpcHQiIHNyYz0iLi4vanMvY29uZmlnLmpzIj4=",
      "length": 53
    }
  ]
}

```

I wanted to validate each Segment type individually, because only the SnipSegment can be without data.  
After going through the docs and this forum, I came up with a solution that I thought should work

```ruby
DataSchema = Dry::Schema.JSON do
  required(:type).filled(:string, eql?: 'DataSegment')
  required(:data).filled(:string)
  required(:length).filled(:integer)
end

SnipSchema = Dry::Schema.JSON do
  required(:type).filled(:string, eql?: 'SnipSegment')
  required(:length).filled(:integer)
end

HighlightSchema = Dry::Schema.JSON do
  required(:type).filled(:string, eql?: 'HighlightSegment')
  required(:data).filled(:string)
  required(:length).filled(:integer)
end

class MySchema < Dry::Validation::Contract
  json do
    required(:response).value(:array).each do
      schema(DataSchema | SnipSchema | HighlightSchema)
    end
  end
end

```

But I get a very strange error hash back:

```auto
{:response=>
  {0=>{:or=>[{:type=>["type is missing"], :data=>["data is missing"], :length=>["length is missing"]}, {:type=>["type is missing"], :length=>["length is missing"]}, {:type=>["type is missing"], :data=>["data is missing"], :length=>["length is missing"]}]},
   1=>{:or=>[{:type=>["type is missing"], :data=>["data is missing"], :length=>["length is missing"]}, {:type=>["type is missing"], :length=>["length is missing"]}, {:type=>["type is missing"], :data=>["data is missing"], :length=>["length is missing"]}]},
   2=>{:or=>[{:type=>["type is missing"], :data=>["data is missing"], :length=>["length is missing"]}, {:type=>["type is missing"], :length=>["length is missing"]}, {:type=>["type is missing"], :data=>["data is missing"], :length=>["length is missing"]}]}}}

```

The `schema(DataSchema | SnipSchema | HighlightSchema)` part receives the hash with string keys, even though I am specifying JSON everywhere.  
Do I need to explicitly tell the segment schemata to symbolize keys, even though they’re of type `Dry::Schema.JSON`? What’s the canonical way to handle such situations?

---

<div class="post-metadata">

**Author:** ![solnic](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.dry-rb.org/solnic/32/779_2.png) [@solnic](https://discourse.dry-rb.org/u/solnic)\
**Post date:** [December 1, 2022, 1:19pm UTC](https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562/2 "2022-12-01T13:19:11Z")

</div>

Please try latest dry-schema and dry-validation. I couldn’t reproduce this with latest versions.

---

<div class="post-metadata">

**Author:** ![rickenharp](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.dry-rb.org/rickenharp/32/12_2.png) [@rickenharp](https://discourse.dry-rb.org/u/rickenharp)\
**Post date:** [December 1, 2022, 1:52pm UTC](https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562/3 "2022-12-01T13:52:53Z")

</div>

I was able to reproduce this with the newest gems, the repo with the code is here: [GitHub - rickenharp/dry-validation-problem](https://github.com/rickenharp/dry-validation-problem)

But I also found an [existing bug report](https://github.com/dry-rb/dry-schema/issues/306) of this phenomenon, because if I change the data to symbolized keys, it suddenly works.

---

<div class="post-metadata">

**Author:** ![solnic](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.dry-rb.org/solnic/32/779_2.png) [@solnic](https://discourse.dry-rb.org/u/solnic)\
**Post date:** [December 1, 2022, 2:23pm UTC](https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562/4 "2022-12-01T14:23:11Z")

</div>

Ah yeah, this makes sense since you used `schema` and it does not imply hash coercion. This is kind of a gotcha. Try this:

```ruby
class MySchema < Dry::Validation::Contract
  json do
    required(:response).array(:hash, DataSchema | SnipSchema | HighlightSchema)
  end
end

```

---

<div class="post-metadata">

**Author:** ![rickenharp](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.dry-rb.org/rickenharp/32/12_2.png) [@rickenharp](https://discourse.dry-rb.org/u/rickenharp)\
**Post date:** [December 1, 2022, 2:39pm UTC](https://discourse.dry-rb.org/t/weird-problem-with-validating-sum-types-from-json/1562/5 "2022-12-01T14:39:46Z")

</div>

Great, this works! Thanks for the quick help!