I disagree that parsing is validating. For example, you could give me a valid ISO date time string, but I want a shipping date and you gave me something in the past. It parses, but is not valid.
I disagree that validating early is bad because some other part of the code might also validate later and possibly do it differently. Yes, that’s bad, but not a reason to not validate early.
This article uses the term “parsing” in a non-standard way - it’s not just about transforming text into structured data, it’s about transforming more general data in to more specific data. For example, you could have a function that “parses” valid dates into valid shipping dates, which returns an error if the input date is in the past for instance and returns a valid_shipping_date type. This type would likely be identical to a normal date, but it would carry extra semantic meaning and would help you to leverage the type checker to make sure that this check actually gets performed.
Doing this would arguably be a bit overzealous, maybe it makes more sense to just parse strings into valid dates and merely validate that they also make sense as shipping dates. Still, any validation can be transformed into a “parse” by simply adding extra type-level information to the validation.
I disagree that parsing is validating. For example, you could give me a valid ISO date time string, but I want a shipping date and you gave me something in the past. It parses, but is not valid.
I disagree that validating early is bad because some other part of the code might also validate later and possibly do it differently. Yes, that’s bad, but not a reason to not validate early.
This article uses the term “parsing” in a non-standard way - it’s not just about transforming text into structured data, it’s about transforming more general data in to more specific data. For example, you could have a function that “parses” valid dates into valid shipping dates, which returns an error if the input date is in the past for instance and returns a
valid_shipping_datetype. This type would likely be identical to a normal date, but it would carry extra semantic meaning and would help you to leverage the type checker to make sure that this check actually gets performed.Doing this would arguably be a bit overzealous, maybe it makes more sense to just parse strings into valid dates and merely validate that they also make sense as shipping dates. Still, any validation can be transformed into a “parse” by simply adding extra type-level information to the validation.