[typescript-fetch] Fix discriminator mapping name

[eriktim]

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The typescript-fetch generator incorrectly using the modelName as the identifier for tagged unions (discriminators). This PR patches that by using the mappingName instead, as this may have been set to an arbitrary value.

cc @TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny @nicokoenig @topce @akehir

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[macjohnny]

thanks for the PR. is mappingName always set? what is its value?

[eriktim]

@macjohnny Yes, in the discriminator.mappedModels it is always set. There are some other edge cases with discriminators that do not seem to work at the moment. I'll create new PRs once/if I run into them.

This fix is for the "Mapping Type Names" in https://swagger.io/docs/specification/data-models/inheritance-and-polymorphism/

[Bessonov]

@eriktim I'm not sure that it's related, but I still get generated converters, which doesn't exists in models. Reproduction:
https://github.com/Bessonov/openapi-bug

git clone https://github.com/Bessonov/openapi-bug
cd openapi-bug
./test.sh

[eriktim]

Ahh I actually do not use oneOf in my spec file. My patch is only for the case where you don't.

But the union type that's being created in your case is great. It seems to lack proper ToJSON/FromJSON functions though. I'm gonna see if I can create another PR for that.

[Bessonov]

@eriktim Thank you for your response! I've experimenting a little bit and come out with following content of modelOneOf.mustache:

{{#hasImports}}
import {
    {{#imports}}
    {{{.}}},
    {{/imports}}
} from './';

{{/hasImports}}
{{#discriminator}}
import {
{{#discriminator.mappedModels}}
    {{modelName}}ToJSON,
    {{modelName}}FromJSONTyped,
{{/discriminator.mappedModels}}
} from './';

{{/discriminator}}
/**
 * @type {{classname}}{{#description}}
 * {{{description}}}{{/description}}
 * @export
 */
export type {{classname}} = {{#oneOf}}{{{.}}}{{^-last}} | {{/-last}}{{/oneOf}};

export function {{classname}}FromJSON(json: any): {{classname}} {
    return {{classname}}FromJSONTyped(json, false);
}

export function {{classname}}FromJSONTyped(json: any, ignoreDiscriminator: boolean): {{classname}} {
{{#discriminator}}
    if (!ignoreDiscriminator) {
{{#discriminator.mappedModels}}
        if (json['{{discriminator.propertyName}}'] === '{{mappingName}}') {
            return {{modelName}}FromJSONTyped(json, true);
        }
{{/discriminator.mappedModels}}
    }
{{/discriminator}}
    throw new Error('unknown discriminator');
}

export function {{classname}}ToJSON(value?: {{classname}} | null): any {
    if (value === undefined) {
        return undefined;
    }
    if (value === null) {
        return null;
    }
    {{#discriminator}}
    {{#discriminator.mappedModels}}
    if (value.{{discriminator.propertyName}} === '{{mappingName}}') {
        return {{modelName}}ToJSON(value);
    }
    {{/discriminator.mappedModels}}
    {{/discriminator}}
    throw new Error('unknown discriminator');
}

[eriktim]

Haha nice, I've come up something similar! Wanted to do a final check tomorrow.

[eriktim]

@Bessonov if you want you can already make a PR. I'll probably add some small comments tomorrow. Otherwise I'll create one tomorrow.

[Bessonov]

@eriktim do that in most convenient way for you, I'm not blocked anymore 👍

[eriktim]

@Bessonov see #4387