fix: [csharp] JsonConverter anyOf creates uncompilable code

[david-marconis]

Using an anyOf with a discriminator creates uncompilable code with cshapr generichost. The issue is that the generated code tries to call a constructor with only one parameter, but the constructor will have multiple parameters.

Steps to reproduce:

# create openapi spec
cat << 'EOF' > modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminatorSimple.yaml
openapi: 3.0.1
info:
   title: fruity
   version: 0.0.1
paths:
   /:
      get:
         responses:
            '200':
               description: desc
               content:
                  application/json:
                     schema:
                        $ref: '#/components/schemas/FruitAnyOfDisc'
components:
   schemas:
    FruitAnyOfDisc:
      anyOf:
        - $ref: '#/components/schemas/AppleAnyOfDisc'
        - $ref: '#/components/schemas/BananaAnyOfDisc'
      discriminator:
        propertyName: fruitType
    AppleAnyOfDisc:
      type: object
      required:
        - fruitType
      properties:
        fruitType:
          type: string
    BananaAnyOfDisc:
      type: object
      required:
        - fruitType
      properties:
        fruitType:
          type: string
EOF
# Generate csharp code
java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g csharp -i modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminatorSimple.yaml -o test
# Build csharp code
dotnet build test

Output:

❯ dotnet build test
Restore complete (0.4s)
  Org.OpenAPITools failed with 2 error(s) and 1 warning(s) (0.3s)
    /home/david/git/openapi-generator/test/src/Org.OpenAPITools/Model/FruitAnyOfDisc.cs(192,28): error CS7036: There is no argument given that corresponds to the required parameter 'bananaAnyOfDisc' of 'FruitAnyOfDisc.FruitAnyOfDisc(Option<AppleAnyOfDisc?>, Option<BananaAnyOfDisc?>)'
    /home/david/git/openapi-generator/test/src/Org.OpenAPITools/Model/FruitAnyOfDisc.cs(195,28): error CS7036: There is no argument given that corresponds to the required parameter 'bananaAnyOfDisc' of 'FruitAnyOfDisc.FruitAnyOfDisc(Option<AppleAnyOfDisc?>, Option<BananaAnyOfDisc?>)'
    /home/david/git/openapi-generator/test/src/Org.OpenAPITools/Model/FruitAnyOfDisc.cs(198,13): warning CS0162: Unreachable code detected

Build failed with 2 error(s) and 1 warning(s) in 0.8s

@mandrean (2017/08) @shibayan (2020/02) @Blackclaws (2021/03) @lucamazzanti (2021/05) @iBicha (2023/07)

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[wing328]

thanks for the PR

cc @devhl-labs

[devhl-labs]

I believe mappedModels is used for the discriminator. I also believe anyOf can have a discriminator so I am not sure this is the right fix.

[david-marconis]

I believe mappedModels is used for the discriminator. I also believe anyOf can have a discriminator so I am not sure this is the right fix.

anyOf can have a discriminator (see my example) and that is the case when this generates uncompilable code.

Right after this in the template there is a special handling for anyOf to set the correct Options. It doesnt't make sense to have the early return and then generate code after as well as it will be unreachable:

            {{#model.composedSchemas.anyOf}}
            Option<{{baseType}}{{>NullConditionalProperty}}> {{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}}ParsedValue = {{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}} == null
                ? default
                : new Option<{{baseType}}{{>NullConditionalProperty}}>({{#lambda.camelcase_sanitize_param}}{{name}}{{/lambda.camelcase_sanitize_param}});
            {{/model.composedSchemas.anyOf}}

If this is not the correct way to solve it, what do you propose @devhl-labs?

[david-marconis]

For context here is the generated code before and after the fix:

            if (!fruitType.IsSet)
                throw new ArgumentException("Property is required for class FruitAnyOfDisc.", nameof(fruitType));

            if (fruitType.IsSet && fruitType.Value == null)
                throw new ArgumentNullException(nameof(fruitType), "Property is not nullable for class FruitAnyOfDisc.");

            if (appleAnyOfDisc != null)
                return new FruitAnyOfDisc(appleAnyOfDisc);

            if (bananaAnyOfDisc != null)
                return new FruitAnyOfDisc(bananaAnyOfDisc);

            throw new JsonException();
            Option<AppleAnyOfDisc?> appleAnyOfDiscParsedValue = appleAnyOfDisc == null
                ? default
                : new Option<AppleAnyOfDisc?>(appleAnyOfDisc);
            Option<BananaAnyOfDisc?> bananaAnyOfDiscParsedValue = bananaAnyOfDisc == null
                ? default
                : new Option<BananaAnyOfDisc?>(bananaAnyOfDisc);

            return new FruitAnyOfDisc(appleAnyOfDiscParsedValue, bananaAnyOfDiscParsedValue);

            if (!fruitType.IsSet)
                throw new ArgumentException("Property is required for class FruitAnyOfDisc.", nameof(fruitType));

            if (fruitType.IsSet && fruitType.Value == null)
                throw new ArgumentNullException(nameof(fruitType), "Property is not nullable for class FruitAnyOfDisc.");

            Option<AppleAnyOfDisc?> appleAnyOfDiscParsedValue = appleAnyOfDisc == null
                ? default
                : new Option<AppleAnyOfDisc?>(appleAnyOfDisc);
            Option<BananaAnyOfDisc?> bananaAnyOfDiscParsedValue = bananaAnyOfDisc == null
                ? default
                : new Option<BananaAnyOfDisc?>(bananaAnyOfDisc);

            return new FruitAnyOfDisc(appleAnyOfDiscParsedValue, bananaAnyOfDiscParsedValue);

[devhl-labs]

You have a discriminator but no mapping. I think we have some issues with mappings anyway so lets merge this so you get unblocked.