From 0ac93a4941839b5f125a84ef636a59cfae4b8e81 Mon Sep 17 00:00:00 2001
From: maikdijkstra <maik@drieam.com>
Date: Wed, 10 Sep 2025 16:43:21 +0200
Subject: [PATCH] fix(ruby-client): Fix incorrect boolean parsing in
 OneOf/AnyOf

Changes the logic of parsing of OneOf/AnyOf to fix incorrect type coercion
in OneOf/AnyOf contexts. The guard which checks whether typed_data is true-ish
fails for booleans. If the oneOf includes a boolean type and the data is false then
it will correctly parse this value as a boolean. However, the guard class will determine
that false is not true-ish and therefore returns nil. So the result of the type coercion
of false will be nil. This can result in problems when dealing with default true.

For example how a false can turn into a true with defaults:
1. The API returns false
2. The type coercion determines false becomes nil
3. When storing this retrieved record with a default of true for this column the stored value is suddenly true
while the API specifically returned false

This fix removes this guard and will rely on the exception raised to return nil when type coercion fails.
---
 .../ruby-client/partial_anyof_module.mustache |   3 +-
 .../ruby-client/partial_oneof_module.mustache |   3 +-
 ...ith-fake-endpoints-models-for-testing.yaml |  30 +++++
 .../ruby-httpx/.openapi-generator/FILES       |   2 +
 samples/client/petstore/ruby-httpx/README.md  |   1 +
 .../ruby-httpx/docs/OneOfPrimitiveTypes.md    |  69 +++++++++++
 .../petstore/ruby-httpx/lib/petstore.rb       |   1 +
 .../lib/petstore/models/mammal_anyof.rb       |   3 +-
 .../models/mammal_without_discriminator.rb    |   3 +-
 .../petstore/models/one_of_primitive_types.rb | 114 ++++++++++++++++++
 .../models/one_of_primitive_types_spec.rb     |  32 +++++
 .../petstore/ruby/.openapi-generator/FILES    |   2 +
 samples/client/petstore/ruby/README.md        |   1 +
 .../petstore/ruby/docs/OneOfPrimitiveTypes.md |  69 +++++++++++
 samples/client/petstore/ruby/lib/petstore.rb  |   1 +
 .../ruby/lib/petstore/models/mammal_anyof.rb  |   3 +-
 .../models/mammal_without_discriminator.rb    |   3 +-
 .../petstore/models/one_of_primitive_types.rb | 114 ++++++++++++++++++
 .../petstore/ruby/spec/custom/model_spec.rb   | 105 +++++++++++++++-
 .../models/one_of_primitive_types_spec.rb     |  32 +++++
 20 files changed, 576 insertions(+), 15 deletions(-)
 create mode 100644 samples/client/petstore/ruby-httpx/docs/OneOfPrimitiveTypes.md
 create mode 100644 samples/client/petstore/ruby-httpx/lib/petstore/models/one_of_primitive_types.rb
 create mode 100644 samples/client/petstore/ruby-httpx/spec/models/one_of_primitive_types_spec.rb
 create mode 100644 samples/client/petstore/ruby/docs/OneOfPrimitiveTypes.md
 create mode 100644 samples/client/petstore/ruby/lib/petstore/models/one_of_primitive_types.rb
 create mode 100644 samples/client/petstore/ruby/spec/models/one_of_primitive_types_spec.rb

diff --git a/modules/openapi-generator/src/main/resources/ruby-client/partial_anyof_module.mustache b/modules/openapi-generator/src/main/resources/ruby-client/partial_anyof_module.mustache
index f979fdd3100e..040a52199e00 100644
--- a/modules/openapi-generator/src/main/resources/ruby-client/partial_anyof_module.mustache
+++ b/modules/openapi-generator/src/main/resources/ruby-client/partial_anyof_module.mustache
@@ -29,8 +29,7 @@
         openapi_any_of.each do |klass|
           begin
             next if klass == :AnyType # "nullable: true"
-            typed_data = find_and_cast_into_type(klass, data)
-            return typed_data if typed_data
+            return find_and_cast_into_type(klass, data)
           rescue # rescue all errors so we keep iterating even if the current item lookup raises
           end
         end
diff --git a/modules/openapi-generator/src/main/resources/ruby-client/partial_oneof_module.mustache b/modules/openapi-generator/src/main/resources/ruby-client/partial_oneof_module.mustache
index 8dd7b381d2bd..04fa0d311024 100644
--- a/modules/openapi-generator/src/main/resources/ruby-client/partial_oneof_module.mustache
+++ b/modules/openapi-generator/src/main/resources/ruby-client/partial_oneof_module.mustache
@@ -69,8 +69,7 @@
         openapi_one_of.each do |klass|
           begin
             next if klass == :AnyType # "nullable: true"
-            typed_data = find_and_cast_into_type(klass, data)
-            return typed_data if typed_data
+            return find_and_cast_into_type(klass, data)
           rescue # rescue all errors so we keep iterating even if the current item lookup raises
           end
         end
diff --git a/modules/openapi-generator/src/test/resources/3_0/ruby/petstore-with-fake-endpoints-models-for-testing.yaml b/modules/openapi-generator/src/test/resources/3_0/ruby/petstore-with-fake-endpoints-models-for-testing.yaml
index 9cdb45fcd65d..064862059da5 100644
--- a/modules/openapi-generator/src/test/resources/3_0/ruby/petstore-with-fake-endpoints-models-for-testing.yaml
+++ b/modules/openapi-generator/src/test/resources/3_0/ruby/petstore-with-fake-endpoints-models-for-testing.yaml
@@ -2162,3 +2162,33 @@ components:
           type: string
         type_:
           type: string
+    OneOfPrimitiveTypes:
+      oneOf:
+        - type: string
+        - type: number
+        - type: integer
+        - type: boolean
+        - type: string
+          format: date
+        - type: string
+          format: date-time
+        - type: array
+          items:
+            type: string
+        - type: array
+          items:
+            type: number
+        - type: array
+          items:
+            type: integer
+        - type: array
+          items:
+            type: boolean
+        - type: array
+          items:
+            type: string
+            format: date
+        - type: array
+          items:
+            type: string
+            format: date-time
diff --git a/samples/client/petstore/ruby-httpx/.openapi-generator/FILES b/samples/client/petstore/ruby-httpx/.openapi-generator/FILES
index 7bc5bf3b003e..fa488c13b2d9 100644
--- a/samples/client/petstore/ruby-httpx/.openapi-generator/FILES
+++ b/samples/client/petstore/ruby-httpx/.openapi-generator/FILES
@@ -48,6 +48,7 @@ docs/Name.md
 docs/NullableClass.md
 docs/NumberOnly.md
 docs/ObjectWithDeprecatedFields.md
+docs/OneOfPrimitiveTypes.md
 docs/Order.md
 docs/OuterComposite.md
 docs/OuterEnum.md
@@ -118,6 +119,7 @@ lib/petstore/models/name.rb
 lib/petstore/models/nullable_class.rb
 lib/petstore/models/number_only.rb
 lib/petstore/models/object_with_deprecated_fields.rb
+lib/petstore/models/one_of_primitive_types.rb
 lib/petstore/models/order.rb
 lib/petstore/models/outer_composite.rb
 lib/petstore/models/outer_enum.rb
diff --git a/samples/client/petstore/ruby-httpx/README.md b/samples/client/petstore/ruby-httpx/README.md
index 3805aba77108..587ccdfcb967 100644
--- a/samples/client/petstore/ruby-httpx/README.md
+++ b/samples/client/petstore/ruby-httpx/README.md
@@ -164,6 +164,7 @@ Class | Method | HTTP request | Description
  - [Petstore::NullableClass](docs/NullableClass.md)
  - [Petstore::NumberOnly](docs/NumberOnly.md)
  - [Petstore::ObjectWithDeprecatedFields](docs/ObjectWithDeprecatedFields.md)
+ - [Petstore::OneOfPrimitiveTypes](docs/OneOfPrimitiveTypes.md)
  - [Petstore::Order](docs/Order.md)
  - [Petstore::OuterComposite](docs/OuterComposite.md)
  - [Petstore::OuterEnum](docs/OuterEnum.md)
diff --git a/samples/client/petstore/ruby-httpx/docs/OneOfPrimitiveTypes.md b/samples/client/petstore/ruby-httpx/docs/OneOfPrimitiveTypes.md
new file mode 100644
index 000000000000..9023811f8f1c
--- /dev/null
+++ b/samples/client/petstore/ruby-httpx/docs/OneOfPrimitiveTypes.md
@@ -0,0 +1,69 @@
+# Petstore::OneOfPrimitiveTypes
+
+## Class instance methods
+
+### `openapi_one_of`
+
+Returns the list of classes defined in oneOf.
+
+#### Example
+
+```ruby
+require 'petstore'
+
+Petstore::OneOfPrimitiveTypes.openapi_one_of
+# =>
+# [
+#   :'Array<Boolean>',
+#   :'Array<Date>',
+#   :'Array<Float>',
+#   :'Array<Integer>',
+#   :'Array<String>',
+#   :'Array<Time>',
+#   :'Boolean',
+#   :'Date',
+#   :'Float',
+#   :'Integer',
+#   :'String',
+#   :'Time'
+# ]
+```
+
+### build
+
+Find the appropriate object from the `openapi_one_of` list and casts the data into it.
+
+#### Example
+
+```ruby
+require 'petstore'
+
+Petstore::OneOfPrimitiveTypes.build(data)
+# => #<Array<Boolean>:0x00007fdd4aab02a0>
+
+Petstore::OneOfPrimitiveTypes.build(data_that_doesnt_match)
+# => nil
+```
+
+#### Parameters
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| **data** | **Mixed** | data to be matched against the list of oneOf items |
+
+#### Return type
+
+- `Array<Boolean>`
+- `Array<Date>`
+- `Array<Float>`
+- `Array<Integer>`
+- `Array<String>`
+- `Array<Time>`
+- `Boolean`
+- `Date`
+- `Float`
+- `Integer`
+- `String`
+- `Time`
+- `nil` (if no type matches)
+
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore.rb b/samples/client/petstore/ruby-httpx/lib/petstore.rb
index 261b537134af..9984140c1e41 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore.rb
@@ -53,6 +53,7 @@
 require 'petstore/models/nullable_class'
 require 'petstore/models/number_only'
 require 'petstore/models/object_with_deprecated_fields'
+require 'petstore/models/one_of_primitive_types'
 require 'petstore/models/order'
 require 'petstore/models/outer_composite'
 require 'petstore/models/outer_enum'
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_anyof.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_anyof.rb
index d9983576863c..5db21348bee0 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_anyof.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_anyof.rb
@@ -37,8 +37,7 @@ def build(data)
         openapi_any_of.each do |klass|
           begin
             next if klass == :AnyType # "nullable: true"
-            typed_data = find_and_cast_into_type(klass, data)
-            return typed_data if typed_data
+            return find_and_cast_into_type(klass, data)
           rescue # rescue all errors so we keep iterating even if the current item lookup raises
           end
         end
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_without_discriminator.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_without_discriminator.rb
index d60058811f7d..7ec87da986be 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_without_discriminator.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/mammal_without_discriminator.rb
@@ -38,8 +38,7 @@ def build(data)
         openapi_one_of.each do |klass|
           begin
             next if klass == :AnyType # "nullable: true"
-            typed_data = find_and_cast_into_type(klass, data)
-            return typed_data if typed_data
+            return find_and_cast_into_type(klass, data)
           rescue # rescue all errors so we keep iterating even if the current item lookup raises
           end
         end
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/one_of_primitive_types.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/one_of_primitive_types.rb
new file mode 100644
index 000000000000..dafa3a0d1817
--- /dev/null
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/one_of_primitive_types.rb
@@ -0,0 +1,114 @@
+=begin
+#OpenAPI Petstore
+
+#This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+The version of the OpenAPI document: 1.0.0
+
+Generated by: https://openapi-generator.tech
+Generator version: 7.16.0-SNAPSHOT
+
+=end
+
+require 'date'
+require 'time'
+
+module Petstore
+  module OneOfPrimitiveTypes
+    class << self
+      # List of class defined in oneOf (OpenAPI v3)
+      def openapi_one_of
+        [
+          :'Array<Boolean>',
+          :'Array<Date>',
+          :'Array<Float>',
+          :'Array<Integer>',
+          :'Array<String>',
+          :'Array<Time>',
+          :'Boolean',
+          :'Date',
+          :'Float',
+          :'Integer',
+          :'String',
+          :'Time'
+        ]
+      end
+
+      # Builds the object
+      # @param [Mixed] Data to be matched against the list of oneOf items
+      # @return [Object] Returns the model or the data itself
+      def build(data)
+        # Go through the list of oneOf items and attempt to identify the appropriate one.
+        # Note:
+        # - We do not attempt to check whether exactly one item matches.
+        # - No advanced validation of types in some cases (e.g. "x: { type: string }" will happily match { x: 123 })
+        #   due to the way the deserialization is made in the base_object template (it just casts without verifying).
+        # - TODO: scalar values are de facto behaving as if they were nullable.
+        # - TODO: logging when debugging is set.
+        openapi_one_of.each do |klass|
+          begin
+            next if klass == :AnyType # "nullable: true"
+            return find_and_cast_into_type(klass, data)
+          rescue # rescue all errors so we keep iterating even if the current item lookup raises
+          end
+        end
+
+        openapi_one_of.include?(:AnyType) ? data : nil
+      end
+
+      private
+
+      SchemaMismatchError = Class.new(StandardError)
+
+      # Note: 'File' is missing here because in the regular case we get the data _after_ a call to JSON.parse.
+      def find_and_cast_into_type(klass, data)
+        return if data.nil?
+
+        case klass.to_s
+        when 'Boolean'
+          return data if data.instance_of?(TrueClass) || data.instance_of?(FalseClass)
+        when 'Float'
+          return data if data.instance_of?(Float)
+        when 'Integer'
+          return data if data.instance_of?(Integer)
+        when 'Time'
+          return Time.parse(data)
+        when 'Date'
+          return Date.iso8601(data)
+        when 'String'
+          return data if data.instance_of?(String)
+        when 'Object' # "type: object"
+          return data if data.instance_of?(Hash)
+        when /\AArray<(?<sub_type>.+)>\z/ # "type: array"
+          if data.instance_of?(Array)
+            sub_type = Regexp.last_match[:sub_type]
+            return data.map { |item| find_and_cast_into_type(sub_type, item) }
+          end
+        when /\AHash<String, (?<sub_type>.+)>\z/ # "type: object" with "additionalProperties: { ... }"
+          if data.instance_of?(Hash) && data.keys.all? { |k| k.instance_of?(Symbol) || k.instance_of?(String) }
+            sub_type = Regexp.last_match[:sub_type]
+            return data.each_with_object({}) { |(k, v), hsh| hsh[k] = find_and_cast_into_type(sub_type, v) }
+          end
+        else # model
+          const = Petstore.const_get(klass)
+          if const
+            if const.respond_to?(:openapi_one_of) # nested oneOf model
+              model = const.build(data)
+              return model if model
+            else
+              # raise if data contains keys that are not known to the model
+              raise if const.respond_to?(:acceptable_attributes) && !(data.keys - const.acceptable_attributes).empty?
+              model = const.build_from_hash(data)
+              return model if model
+            end
+          end
+        end
+
+        raise # if no match by now, raise
+      rescue
+        raise SchemaMismatchError, "#{data} doesn't match the #{klass} type"
+      end
+    end
+  end
+
+end
diff --git a/samples/client/petstore/ruby-httpx/spec/models/one_of_primitive_types_spec.rb b/samples/client/petstore/ruby-httpx/spec/models/one_of_primitive_types_spec.rb
new file mode 100644
index 000000000000..8ab4c1cd193b
--- /dev/null
+++ b/samples/client/petstore/ruby-httpx/spec/models/one_of_primitive_types_spec.rb
@@ -0,0 +1,32 @@
+=begin
+#OpenAPI Petstore
+
+#This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+The version of the OpenAPI document: 1.0.0
+
+Generated by: https://openapi-generator.tech
+Generator version: 7.16.0-SNAPSHOT
+
+=end
+
+require 'spec_helper'
+require 'json'
+require 'date'
+
+# Unit tests for Petstore::OneOfPrimitiveTypes
+# Automatically generated by openapi-generator (https://openapi-generator.tech)
+# Please update as you see appropriate
+describe Petstore::OneOfPrimitiveTypes do
+  describe '.openapi_one_of' do
+    it 'lists the items referenced in the oneOf array' do
+      expect(described_class.openapi_one_of).to_not be_empty
+    end
+  end
+
+  describe '.build' do
+    it 'returns the correct model' do
+      # assertion here. ref: https://rspec.info/features/3-12/rspec-expectations/built-in-matchers/
+    end
+  end
+end
diff --git a/samples/client/petstore/ruby/.openapi-generator/FILES b/samples/client/petstore/ruby/.openapi-generator/FILES
index 7bc5bf3b003e..fa488c13b2d9 100644
--- a/samples/client/petstore/ruby/.openapi-generator/FILES
+++ b/samples/client/petstore/ruby/.openapi-generator/FILES
@@ -48,6 +48,7 @@ docs/Name.md
 docs/NullableClass.md
 docs/NumberOnly.md
 docs/ObjectWithDeprecatedFields.md
+docs/OneOfPrimitiveTypes.md
 docs/Order.md
 docs/OuterComposite.md
 docs/OuterEnum.md
@@ -118,6 +119,7 @@ lib/petstore/models/name.rb
 lib/petstore/models/nullable_class.rb
 lib/petstore/models/number_only.rb
 lib/petstore/models/object_with_deprecated_fields.rb
+lib/petstore/models/one_of_primitive_types.rb
 lib/petstore/models/order.rb
 lib/petstore/models/outer_composite.rb
 lib/petstore/models/outer_enum.rb
diff --git a/samples/client/petstore/ruby/README.md b/samples/client/petstore/ruby/README.md
index 3805aba77108..587ccdfcb967 100644
--- a/samples/client/petstore/ruby/README.md
+++ b/samples/client/petstore/ruby/README.md
@@ -164,6 +164,7 @@ Class | Method | HTTP request | Description
  - [Petstore::NullableClass](docs/NullableClass.md)
  - [Petstore::NumberOnly](docs/NumberOnly.md)
  - [Petstore::ObjectWithDeprecatedFields](docs/ObjectWithDeprecatedFields.md)
+ - [Petstore::OneOfPrimitiveTypes](docs/OneOfPrimitiveTypes.md)
  - [Petstore::Order](docs/Order.md)
  - [Petstore::OuterComposite](docs/OuterComposite.md)
  - [Petstore::OuterEnum](docs/OuterEnum.md)
diff --git a/samples/client/petstore/ruby/docs/OneOfPrimitiveTypes.md b/samples/client/petstore/ruby/docs/OneOfPrimitiveTypes.md
new file mode 100644
index 000000000000..9023811f8f1c
--- /dev/null
+++ b/samples/client/petstore/ruby/docs/OneOfPrimitiveTypes.md
@@ -0,0 +1,69 @@
+# Petstore::OneOfPrimitiveTypes
+
+## Class instance methods
+
+### `openapi_one_of`
+
+Returns the list of classes defined in oneOf.
+
+#### Example
+
+```ruby
+require 'petstore'
+
+Petstore::OneOfPrimitiveTypes.openapi_one_of
+# =>
+# [
+#   :'Array<Boolean>',
+#   :'Array<Date>',
+#   :'Array<Float>',
+#   :'Array<Integer>',
+#   :'Array<String>',
+#   :'Array<Time>',
+#   :'Boolean',
+#   :'Date',
+#   :'Float',
+#   :'Integer',
+#   :'String',
+#   :'Time'
+# ]
+```
+
+### build
+
+Find the appropriate object from the `openapi_one_of` list and casts the data into it.
+
+#### Example
+
+```ruby
+require 'petstore'
+
+Petstore::OneOfPrimitiveTypes.build(data)
+# => #<Array<Boolean>:0x00007fdd4aab02a0>
+
+Petstore::OneOfPrimitiveTypes.build(data_that_doesnt_match)
+# => nil
+```
+
+#### Parameters
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| **data** | **Mixed** | data to be matched against the list of oneOf items |
+
+#### Return type
+
+- `Array<Boolean>`
+- `Array<Date>`
+- `Array<Float>`
+- `Array<Integer>`
+- `Array<String>`
+- `Array<Time>`
+- `Boolean`
+- `Date`
+- `Float`
+- `Integer`
+- `String`
+- `Time`
+- `nil` (if no type matches)
+
diff --git a/samples/client/petstore/ruby/lib/petstore.rb b/samples/client/petstore/ruby/lib/petstore.rb
index 261b537134af..9984140c1e41 100644
--- a/samples/client/petstore/ruby/lib/petstore.rb
+++ b/samples/client/petstore/ruby/lib/petstore.rb
@@ -53,6 +53,7 @@
 require 'petstore/models/nullable_class'
 require 'petstore/models/number_only'
 require 'petstore/models/object_with_deprecated_fields'
+require 'petstore/models/one_of_primitive_types'
 require 'petstore/models/order'
 require 'petstore/models/outer_composite'
 require 'petstore/models/outer_enum'
diff --git a/samples/client/petstore/ruby/lib/petstore/models/mammal_anyof.rb b/samples/client/petstore/ruby/lib/petstore/models/mammal_anyof.rb
index d9983576863c..5db21348bee0 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/mammal_anyof.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/mammal_anyof.rb
@@ -37,8 +37,7 @@ def build(data)
         openapi_any_of.each do |klass|
           begin
             next if klass == :AnyType # "nullable: true"
-            typed_data = find_and_cast_into_type(klass, data)
-            return typed_data if typed_data
+            return find_and_cast_into_type(klass, data)
           rescue # rescue all errors so we keep iterating even if the current item lookup raises
           end
         end
diff --git a/samples/client/petstore/ruby/lib/petstore/models/mammal_without_discriminator.rb b/samples/client/petstore/ruby/lib/petstore/models/mammal_without_discriminator.rb
index d60058811f7d..7ec87da986be 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/mammal_without_discriminator.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/mammal_without_discriminator.rb
@@ -38,8 +38,7 @@ def build(data)
         openapi_one_of.each do |klass|
           begin
             next if klass == :AnyType # "nullable: true"
-            typed_data = find_and_cast_into_type(klass, data)
-            return typed_data if typed_data
+            return find_and_cast_into_type(klass, data)
           rescue # rescue all errors so we keep iterating even if the current item lookup raises
           end
         end
diff --git a/samples/client/petstore/ruby/lib/petstore/models/one_of_primitive_types.rb b/samples/client/petstore/ruby/lib/petstore/models/one_of_primitive_types.rb
new file mode 100644
index 000000000000..dafa3a0d1817
--- /dev/null
+++ b/samples/client/petstore/ruby/lib/petstore/models/one_of_primitive_types.rb
@@ -0,0 +1,114 @@
+=begin
+#OpenAPI Petstore
+
+#This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+The version of the OpenAPI document: 1.0.0
+
+Generated by: https://openapi-generator.tech
+Generator version: 7.16.0-SNAPSHOT
+
+=end
+
+require 'date'
+require 'time'
+
+module Petstore
+  module OneOfPrimitiveTypes
+    class << self
+      # List of class defined in oneOf (OpenAPI v3)
+      def openapi_one_of
+        [
+          :'Array<Boolean>',
+          :'Array<Date>',
+          :'Array<Float>',
+          :'Array<Integer>',
+          :'Array<String>',
+          :'Array<Time>',
+          :'Boolean',
+          :'Date',
+          :'Float',
+          :'Integer',
+          :'String',
+          :'Time'
+        ]
+      end
+
+      # Builds the object
+      # @param [Mixed] Data to be matched against the list of oneOf items
+      # @return [Object] Returns the model or the data itself
+      def build(data)
+        # Go through the list of oneOf items and attempt to identify the appropriate one.
+        # Note:
+        # - We do not attempt to check whether exactly one item matches.
+        # - No advanced validation of types in some cases (e.g. "x: { type: string }" will happily match { x: 123 })
+        #   due to the way the deserialization is made in the base_object template (it just casts without verifying).
+        # - TODO: scalar values are de facto behaving as if they were nullable.
+        # - TODO: logging when debugging is set.
+        openapi_one_of.each do |klass|
+          begin
+            next if klass == :AnyType # "nullable: true"
+            return find_and_cast_into_type(klass, data)
+          rescue # rescue all errors so we keep iterating even if the current item lookup raises
+          end
+        end
+
+        openapi_one_of.include?(:AnyType) ? data : nil
+      end
+
+      private
+
+      SchemaMismatchError = Class.new(StandardError)
+
+      # Note: 'File' is missing here because in the regular case we get the data _after_ a call to JSON.parse.
+      def find_and_cast_into_type(klass, data)
+        return if data.nil?
+
+        case klass.to_s
+        when 'Boolean'
+          return data if data.instance_of?(TrueClass) || data.instance_of?(FalseClass)
+        when 'Float'
+          return data if data.instance_of?(Float)
+        when 'Integer'
+          return data if data.instance_of?(Integer)
+        when 'Time'
+          return Time.parse(data)
+        when 'Date'
+          return Date.iso8601(data)
+        when 'String'
+          return data if data.instance_of?(String)
+        when 'Object' # "type: object"
+          return data if data.instance_of?(Hash)
+        when /\AArray<(?<sub_type>.+)>\z/ # "type: array"
+          if data.instance_of?(Array)
+            sub_type = Regexp.last_match[:sub_type]
+            return data.map { |item| find_and_cast_into_type(sub_type, item) }
+          end
+        when /\AHash<String, (?<sub_type>.+)>\z/ # "type: object" with "additionalProperties: { ... }"
+          if data.instance_of?(Hash) && data.keys.all? { |k| k.instance_of?(Symbol) || k.instance_of?(String) }
+            sub_type = Regexp.last_match[:sub_type]
+            return data.each_with_object({}) { |(k, v), hsh| hsh[k] = find_and_cast_into_type(sub_type, v) }
+          end
+        else # model
+          const = Petstore.const_get(klass)
+          if const
+            if const.respond_to?(:openapi_one_of) # nested oneOf model
+              model = const.build(data)
+              return model if model
+            else
+              # raise if data contains keys that are not known to the model
+              raise if const.respond_to?(:acceptable_attributes) && !(data.keys - const.acceptable_attributes).empty?
+              model = const.build_from_hash(data)
+              return model if model
+            end
+          end
+        end
+
+        raise # if no match by now, raise
+      rescue
+        raise SchemaMismatchError, "#{data} doesn't match the #{klass} type"
+      end
+    end
+  end
+
+end
diff --git a/samples/client/petstore/ruby/spec/custom/model_spec.rb b/samples/client/petstore/ruby/spec/custom/model_spec.rb
index 8e7af2c0db3e..c361ec6e2a66 100644
--- a/samples/client/petstore/ruby/spec/custom/model_spec.rb
+++ b/samples/client/petstore/ruby/spec/custom/model_spec.rb
@@ -25,7 +25,7 @@
       expect(result2).to be_a Petstore::Zebra
 
       # invalid data/hash should result in nil
-      result3 = Petstore::MammalAnyof.build({"something": 123})
+      result3 = Petstore::MammalAnyof.build({ "something": 123 })
       expect(result3).to be_nil
     end
   end
@@ -46,7 +46,7 @@
       expect(result2).to be_a Petstore::Zebra
 
       # invalid data/hash should result in nil
-      result3 = Petstore::Mammal.build({"something": 123})
+      result3 = Petstore::Mammal.build({ "something": 123 })
       expect(result3).to be_nil
     end
 
@@ -65,9 +65,108 @@
       expect(result2).to be_a Petstore::Zebra
 
       # invalid data/hash should result in nil
-      result3 = Petstore::MammalWithoutDiscriminator.build({"something": 123})
+      result3 = Petstore::MammalWithoutDiscriminator.build({ "something": 123 })
       expect(result3).to be_nil
     end
 
   end
 end
+
+describe 'OneOfPrimitiveTypes' do
+  it 'should be able to parse integer' do
+    int_value = Petstore::OneOfPrimitiveTypes.build(
+      123
+    )
+    expect(int_value).to eq 123
+  end
+  it 'should be able to parse float' do
+    float_value = Petstore::OneOfPrimitiveTypes.build(
+      123.45
+    )
+    expect(float_value).to eq 123.45
+  end
+  it 'should be able to parse string' do
+    string_value = Petstore::OneOfPrimitiveTypes.build(
+      'ABC1'
+    )
+    expect(string_value).to eq 'ABC1'
+  end
+  it 'should be able to parse date' do
+    date_value = Petstore::OneOfPrimitiveTypes.build(
+      '2020-01-02'
+    )
+    expect(date_value).to be_a Date
+    expect(date_value).to eq Date.iso8601('2020-01-02')
+  end
+  it 'should be able to parse date time' do
+    datetime_value = Petstore::OneOfPrimitiveTypes.build(
+      '2020-01-02T12:34:56Z'
+    )
+    expect(datetime_value).to eq Date.iso8601('2020-01-02T12:34:56Z')
+  end
+  it 'should be able to parse boolean' do
+    false_value = Petstore::OneOfPrimitiveTypes.build(
+      false
+    )
+    expect(false_value).to eq false
+
+    true_value = Petstore::OneOfPrimitiveTypes.build(
+      true
+    )
+    expect(true_value).to eq true
+  end
+  it 'should be able to parse array of integer' do
+    array_value = Petstore::OneOfPrimitiveTypes.build(
+      [1, 2, 3]
+    )
+    expect(array_value).to be_a Array
+    expect(array_value).to eq [1, 2, 3]
+  end
+  it 'should be able to parse array of string' do
+    array_value = Petstore::OneOfPrimitiveTypes.build(
+      %w[ABC1 DEF2 GHI3]
+    )
+    expect(array_value).to be_a Array
+    expect(array_value).to eq %w[ABC1 DEF2 GHI3]
+  end
+  it 'should be able to parse array of float' do
+    array_value = Petstore::OneOfPrimitiveTypes.build(
+      [1.1, 2.2, 3.3]
+    )
+    expect(array_value).to be_a Array
+    expect(array_value).to eq [1.1, 2.2, 3.3]
+  end
+  it 'should be able to parse array of date' do
+    array_value = Petstore::OneOfPrimitiveTypes.build(
+      %w[2020-01-02 2020-03-04]
+    )
+    expect(array_value).to be_a Array
+    expect(array_value).to eq [Date.iso8601('2020-01-02'), Date.iso8601('2020-03-04')]
+  end
+  it 'should be able to parse an invalid date' do
+    invalid_date_value = Petstore::OneOfPrimitiveTypes.build(
+      '2020-13-02'
+    )
+    expect(invalid_date_value).to eq '2020-13-02'
+  end
+  it 'should be able to parse array of date time' do
+    array_value = Petstore::OneOfPrimitiveTypes.build(
+      %w[2020-01-02T12:34:56Z 2020-03-04T01:23:45Z]
+    )
+    expect(array_value).to be_a Array
+    expect(array_value).to eq [Date.parse('2020-01-02T12:34:56Z'), Date.parse('2020-03-04T01:23:45Z')]
+  end
+  it 'should be able to parse array of boolean' do
+    array_value = Petstore::OneOfPrimitiveTypes.build(
+      [true, false, true]
+    )
+    expect(array_value).to be_a Array
+    expect(array_value).to eq [true, false, true]
+  end
+  it 'should return nil for unsupported type' do
+    unsupported_value = Petstore::OneOfPrimitiveTypes.build(
+      { foo: 'bar' }
+    )
+    expect(unsupported_value).to be_nil
+  end
+end
diff --git a/samples/client/petstore/ruby/spec/models/one_of_primitive_types_spec.rb b/samples/client/petstore/ruby/spec/models/one_of_primitive_types_spec.rb
new file mode 100644
index 000000000000..8ab4c1cd193b
--- /dev/null
+++ b/samples/client/petstore/ruby/spec/models/one_of_primitive_types_spec.rb
@@ -0,0 +1,32 @@
+=begin
+#OpenAPI Petstore
+
+#This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+The version of the OpenAPI document: 1.0.0
+
+Generated by: https://openapi-generator.tech
+Generator version: 7.16.0-SNAPSHOT
+
+=end
+
+require 'spec_helper'
+require 'json'
+require 'date'
+
+# Unit tests for Petstore::OneOfPrimitiveTypes
+# Automatically generated by openapi-generator (https://openapi-generator.tech)
+# Please update as you see appropriate
+describe Petstore::OneOfPrimitiveTypes do
+  describe '.openapi_one_of' do
+    it 'lists the items referenced in the oneOf array' do
+      expect(described_class.openapi_one_of).to_not be_empty
+    end
+  end
+
+  describe '.build' do
+    it 'returns the correct model' do
+      # assertion here. ref: https://rspec.info/features/3-12/rspec-expectations/built-in-matchers/
+    end
+  end
+end