Type 'string' is not assignable to type 'keyof CustomerInput'

I know this question was asked multiple times but at this point, I feel like this error could show up in multiple cases and I can’t find the answer to this problem.

Here is the type that I have:

export type CustomerInput = {
  email: string;
  firstName?: string;
  lastName?: string;
  phone?: string;
  id?: string;
  locale?: string;
  tags?: string;
  metafields?: Array<MetafieldInput>;
  acceptsMarketing?: boolean;
  acceptsMarketingUpdatedAt?: string;
  marketingOptInLevel?: CustomerMarketingOptInLevel;
  addresses?: Array<AddressInput>;
  note?: string;
  privateMetafields?: Array<PrivateMetafieldInput>;
  smsMarketingConsent?: CustomerSmsMarketingConsentInput;
  taxExempt?: boolean;
  taxExemptions?: Array<string>;
};

I am trying to map other type to return object: CustomerInput like so:

  const customerInput: CustomerInput = {
    email: ''
  };

  Object.keys(row).forEach((property: string) => {

    let propValue = row[property as keyof ExcelRow] as boolean | string;
  
    if (propValue === 'false') {
      propValue = false;
    } else if (propValue === 'true') {
      propValue = true;
    }

    // ...

    if (property && property.startsWith('CustomerInput.')) {
      // Type 'string' is not assignable to type 'keyof CustomerInput'
      const customerProperty: keyof CustomerInput = property.replace('CustomerInput.', '');
      if (customerProperty.length > 0 && customerProperty) {
        // Type 'string | boolean' is not assignable to type 'never'.
        // Type 'string' is not assignable to type 'never'.ts(2322)
        customerInput[customerProperty] = propValue;
      } 
    }
  });

What am I doing wrong?

>Solution :

replace returns string type, you cannot assert a string to be keyof CustomerInput. If you know that string replacement will return CustomerInput key certainly, you can cast it by as like below:

const customerProperty: keyof CustomerInput = property.replace('CustomerInput.', '') as keyof CustomerInput

For the second case, you can reassign the object instead of direct value assignment

customerInput = {
    ...customerInput,
    [customerProperty]: propValue
  }

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