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Fix Swift oneOf discriminator decoding with enumUnknownDefaultCase #22635

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4brunu merged 4 commits into from
Jan 12, 2026
+136 −6
Merged

Fix Swift oneOf discriminator decoding with enumUnknownDefaultCase #22635

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6f6f05c
Fix Swift oneOf discriminator decoding with enumUnknownDefaultCase
lastMove Jan 8, 2026
4165a5d
Remove comments from modelOneOf templates
lastMove Jan 8, 2026
96b6a88
Add tests for oneOf discriminator-first decoding
lastMove Jan 8, 2026
74aa743
Fix whitespace in Swift oneOf templates
lastMove Jan 12, 2026
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35 changes: 34 additions & 1 deletion modules/openapi-generator/src/main/resources/swift5/modelOneOf.mustache
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Original file line number Diff line number Diff line change
Expand Up @@ -14,13 +14,45 @@
try container.encode(value)
{{/oneOf}}
{{#oneOfUnknownDefaultCase}}
case unknownDefaultOpenApi(let type):
case .unknownDefaultOpenApi:
try container.encodeNil()
{{/oneOfUnknownDefaultCase}}
}
}

{{#discriminator}}
private enum DiscriminatorCodingKey: String, CodingKey {
case {{discriminator.propertyName}} = "{{discriminator.propertyBaseName}}"
}
{{/discriminator}}

public init(from decoder: Decoder) throws {
{{#discriminator}}
// Discriminator-based decoding: read discriminator value first, then decode the correct variant
let keyedContainer = try decoder.container(keyedBy: DiscriminatorCodingKey.self)
let discriminatorValue = try keyedContainer.decode(String.self, forKey: .{{discriminator.propertyName}})

switch discriminatorValue {
{{#discriminator.mappedModels}}
case "{{mappingName}}":
self = .type{{modelName}}(try {{modelName}}(from: decoder))
{{/discriminator.mappedModels}}
default:
{{#oneOfUnknownDefaultCase}}
self = .unknownDefaultOpenApi
{{/oneOfUnknownDefaultCase}}
{{^oneOfUnknownDefaultCase}}
throw DecodingError.dataCorrupted(
DecodingError.Context(
codingPath: decoder.codingPath,
debugDescription: "Unknown discriminator value '\(discriminatorValue)' for {{classname}}"
)
)
{{/oneOfUnknownDefaultCase}}
}
{{/discriminator}}
{{^discriminator}}
// No discriminator: try each type sequentially
let container = try decoder.singleValueContainer()
{{#oneOf}}
{{#-first}}
Expand All @@ -39,5 +71,6 @@
throw DecodingError.typeMismatch(Self.Type.self, .init(codingPath: decoder.codingPath, debugDescription: "Unable to decode instance of {{classname}}"))
{{/oneOfUnknownDefaultCase}}
}
{{/discriminator}}
}
}
35 changes: 34 additions & 1 deletion modules/openapi-generator/src/main/resources/swift6/modelOneOf.mustache
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Original file line number Diff line number Diff line change
Expand Up @@ -14,13 +14,45 @@
try container.encode(value)
{{/oneOf}}
{{#oneOfUnknownDefaultCase}}
case unknownDefaultOpenApi(let type):
case .unknownDefaultOpenApi:
try container.encodeNil()
{{/oneOfUnknownDefaultCase}}
}
}

{{#discriminator}}
private enum DiscriminatorCodingKey: String, CodingKey {
case {{discriminator.propertyName}} = "{{discriminator.propertyBaseName}}"
}
{{/discriminator}}
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@4brunu 4brunu Jan 12, 2026 •
edited
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@lastMove can you give a new line before {{/discriminator}} and remove the new line after the {{/discriminator}}? I'm trying to avoid the new line in the Fruit.swift files

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@lastMove lastMove Jan 12, 2026

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@4brunu done. I am not totally happy with the way I did it though. I tried to use mustache whitespace control prefixes but it seems to not be supported with the version of mustache we are using. So I had to remove some indentation in the template to make it work. Maybe you have a better way ?


public init(from decoder: Decoder) throws {
{{#discriminator}}
// Discriminator-based decoding: read discriminator value first, then decode the correct variant
let keyedContainer = try decoder.container(keyedBy: DiscriminatorCodingKey.self)
let discriminatorValue = try keyedContainer.decode(String.self, forKey: .{{discriminator.propertyName}})

switch discriminatorValue {
{{#discriminator.mappedModels}}
case "{{mappingName}}":
self = .type{{#transformArrayType}}{{modelName}}{{/transformArrayType}}(try {{modelName}}(from: decoder))
{{/discriminator.mappedModels}}
default:
{{#oneOfUnknownDefaultCase}}
self = .unknownDefaultOpenApi
{{/oneOfUnknownDefaultCase}}
{{^oneOfUnknownDefaultCase}}
throw DecodingError.dataCorrupted(
DecodingError.Context(
codingPath: decoder.codingPath,
debugDescription: "Unknown discriminator value '\(discriminatorValue)' for {{classname}}"
)
)
{{/oneOfUnknownDefaultCase}}
}
{{/discriminator}}
{{^discriminator}}
// No discriminator: try each type sequentially
let container = try decoder.singleValueContainer()
{{#oneOf}}
{{#-first}}
Expand All @@ -39,5 +71,6 @@
throw DecodingError.typeMismatch(Self.Type.self, .init(codingPath: decoder.codingPath, debugDescription: "Unable to decode instance of {{classname}}"))
{{/oneOfUnknownDefaultCase}}
}
{{/discriminator}}
}
}
2 changes: 2 additions & 0 deletions samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,9 @@ public enum Fruit: Codable, JSONEncodable, Hashable {
}
}


public init(from decoder: Decoder) throws {
// No discriminator: try each type sequentially
let container = try decoder.singleValueContainer()
if let value = try? container.decode(Apple.self) {
self = .typeApple(value)
Expand Down
2 changes: 2 additions & 0 deletions samples/client/petstore/swift6/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,9 @@ public enum Fruit: Sendable, Codable, ParameterConvertible, Hashable {
}
}


public init(from decoder: Decoder) throws {
// No discriminator: try each type sequentially
let container = try decoder.singleValueContainer()
if let value = try? container.decode(Apple.self) {
self = .typeApple(value)
Expand Down