Shows an issue with DateTime type for OpenAPI generator

Scenario

We use the OpenAPI generator tooling to generate a Typescript Axios client for a swagger definition which has a date-time parameter. However for our purpose we type map the date object to string using --type-mappings Date=string (this subsequently also maps date-time to string).

"parameters": [
    {
        "name": "param",
        "in": "query",
        "required": false,
        "type": "string",
        "format": "date-time"
    }
],

Issue description

The generated code arguments appear correctly as string, but a toISOString() call is still executed.

example(param?: string, options: any = {}): RequestArgs {
    ....
    if (param !== undefined) {
        localVarQueryParameter['param'] = (param as any).toISOString(); <-- toISOString() on string type
    }
    ...
},

Solution

A fix was applied to date template where a instanceof Date check was added to prevent this. The same fix should be applied to the date-time type. OpenAPITools/openapi-generator#3423

// this fix was applied to date type
localVarQueryParameter['{{baseName}}'] = ({{paramName}} as any instanceof Date) ?
    ({{paramName}} as any).toISOString().substr(0,10) :
    {{paramName}};

// this fix can be applied to date-time
localVarQueryParameter['{{baseName}}'] = ({{paramName}} as any instanceof Date) ?
    ({{paramName}} as any).toISOString() :
    {{paramName}};

I have opened a PR here for it here