5 ms·

TypeScript: Template string types and mapped type 'as' clauses

31 points by Kinrany 6y ago

chadlavi 6y ago
I still really, really want RegExp types
- reificator 6y ago
  Is the javascript regex literal or builtin RegExp type not sufficient for your needs? What are they missing? https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
  - tengbretson 6y ago
    I think the op is asking for actual type refinement by a regex condition.
    - reificator 6y ago
      That would make a lot of sense given the topic at hand. Thanks for the clarification.
    - chadlavi 6y ago
      especially as a library maintainer, I would really love to be able to say, for example, "you have to pass an email address to this prop" or "you have to pass a US phone number"
      - pseudonom- 6y ago
        This can be fairly smoothly achieved already: https://dev.to/gcanti/functional-design-smart-constructors-14nb https://dev.to/gcanti/functional-design-smart-constructors-1...
        chadlavi 6y ago
        Yeah I'm familiar with branded types, but they're cumbersome and require API changes beyond just type narrowing to implement. I just wish they'd figure out how to implement strong types in typescript without js side effects.
      - reificator 6y ago
        So you're the one I should blame whenever some regex fails to validate my perfectly standards compliant email address! I get very frustrated when I sign up for storefronts using an email with a `.dev` address and some wanker decides that I shouldn't be allowed to give them money because my email address doesn't end in `@gmail.com`. Stop this. Regex is not the right tool for this job. If you're going to use the regex hammer at least use the full standards compliant one shown here: https://stackoverflow.com/a/201378 https://stackoverflow.com/a/201378 > The problem with regular expressions is that telling someone that their perfectly valid e-mail address is invalid (a false positive) because your regular expression can't handle it is just rude and impolite from the user's perspective. A state engine for the purpose can both validate and even correct e-mail addresses that would otherwise be considered invalid as it disassembles the e-mail address according to each RFC.
        chadlavi 6y ago
        No, it's an inner-source library, but thanks for expressing your generalized frustration at me! But also I would use a standards-compliant regex. I also hate it when people don't implement standards to spec.
        spicybright 6y ago
        Or if you're even too lazy for that, just match `.+@.+` and handle errors properly if sending an email fails (which you'll obviously have to handle anyways as a valid email address might not be in service)
throwaway189262 6y ago
Ok for real, is Typescript going to collapse one day from the complexity of its type system? Typescript's type system became Turing complete years ago, and hilariously, someone linked that issue to the new types mentioned in this post :) https://github.com/microsoft/TypeScript/issues/14833 https://github.com/microsoft/TypeScript/issues/14833 I've been using Typescript for years, and I still like it. But I'm starting to get frustrated by the sheer amount of "stuff" they keep adding to the type system. My coworkers are too. They don't want to spend weeks reading about "advanced types", just want TS to be a nice wrapper around JS. Typescript doesn't have a standard library or a runtime, so eventually can't they just call it done? Just do occasional maintenance releases to keep up with new JS features
- mekster 6y ago
  What is wrong just using what you're comfortable with? Why are you asking TS to halt any new feature development because you don't want to keep up?
- gmac 6y ago
  On the one hand, yes, the code examples in that PR thread are kind of terrifying. On the other, the ability to map mechanically between type names would be really useful, and is something I’ve previously wished for. It would, for example, enormously simplify type generation for Zapatos[1], which currently creates multiple long object mappings for this purpose, such as: export type SelectableForTable<T extends Table> = { accounts: accounts.Selectable; appleTransactions: appleTransactions.Selectable; authors: authors.Selectable; books: books.Selectable; emailAuthentication: emailAuthentication.Selectable; employees: employees.Selectable; identityTest: identityTest.Selectable; stores: stores.Selectable; tags: tags.Selectable; tableInOtherSchema: tableInOtherSchema.Selectable; }[T]; [1] https://jawj.github.io/zapatos/ https://jawj.github.io/zapatos/
  - Kinrany 6y ago
    Since you're generating types anyway, can't this be simplified to `tableTypes[T]['Selectable']`?

31 points by Kinrany 6y ago

chadlavi 6y ago

I still really, really want RegExp types

reificator 6y ago
Is the javascript regex literal or builtin RegExp type not sufficient for your needs? What are they missing? https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
- tengbretson 6y ago
  I think the op is asking for actual type refinement by a regex condition.
  - reificator 6y ago
    That would make a lot of sense given the topic at hand. Thanks for the clarification.
  - chadlavi 6y ago
    especially as a library maintainer, I would really love to be able to say, for example, "you have to pass an email address to this prop" or "you have to pass a US phone number"
    - pseudonom- 6y ago
      This can be fairly smoothly achieved already: https://dev.to/gcanti/functional-design-smart-constructors-14nb https://dev.to/gcanti/functional-design-smart-constructors-1...
      - chadlavi 6y ago
        Yeah I'm familiar with branded types, but they're cumbersome and require API changes beyond just type narrowing to implement. I just wish they'd figure out how to implement strong types in typescript without js side effects.
    - reificator 6y ago
      So you're the one I should blame whenever some regex fails to validate my perfectly standards compliant email address! I get very frustrated when I sign up for storefronts using an email with a `.dev` address and some wanker decides that I shouldn't be allowed to give them money because my email address doesn't end in `@gmail.com`. Stop this. Regex is not the right tool for this job. If you're going to use the regex hammer at least use the full standards compliant one shown here: https://stackoverflow.com/a/201378 https://stackoverflow.com/a/201378 > The problem with regular expressions is that telling someone that their perfectly valid e-mail address is invalid (a false positive) because your regular expression can't handle it is just rude and impolite from the user's perspective. A state engine for the purpose can both validate and even correct e-mail addresses that would otherwise be considered invalid as it disassembles the e-mail address according to each RFC.
      - chadlavi 6y ago
        No, it's an inner-source library, but thanks for expressing your generalized frustration at me! But also I would use a standards-compliant regex. I also hate it when people don't implement standards to spec.
      - spicybright 6y ago
        Or if you're even too lazy for that, just match `.+@.+` and handle errors properly if sending an email fails (which you'll obviously have to handle anyways as a valid email address might not be in service)

throwaway189262 6y ago

Ok for real, is Typescript going to collapse one day from the complexity of its type system? Typescript's type system became Turing complete years ago, and hilariously, someone linked that issue to the new types mentioned in this post :) https://github.com/microsoft/TypeScript/issues/14833 https://github.com/microsoft/TypeScript/issues/14833 I've been using Typescript for years, and I still like it. But I'm starting to get frustrated by the sheer amount of "stuff" they keep adding to the type system. My coworkers are too. They don't want to spend weeks reading about "advanced types", just want TS to be a nice wrapper around JS. Typescript doesn't have a standard library or a runtime, so eventually can't they just call it done? Just do occasional maintenance releases to keep up with new JS features

mekster 6y ago
What is wrong just using what you're comfortable with? Why are you asking TS to halt any new feature development because you don't want to keep up?
gmac 6y ago
On the one hand, yes, the code examples in that PR thread are kind of terrifying. On the other, the ability to map mechanically between type names would be really useful, and is something I’ve previously wished for. It would, for example, enormously simplify type generation for Zapatos[1], which currently creates multiple long object mappings for this purpose, such as: export type SelectableForTable<T extends Table> = { accounts: accounts.Selectable; appleTransactions: appleTransactions.Selectable; authors: authors.Selectable; books: books.Selectable; emailAuthentication: emailAuthentication.Selectable; employees: employees.Selectable; identityTest: identityTest.Selectable; stores: stores.Selectable; tags: tags.Selectable; tableInOtherSchema: tableInOtherSchema.Selectable; }[T]; [1] https://jawj.github.io/zapatos/ https://jawj.github.io/zapatos/
- Kinrany 6y ago
  Since you're generating types anyway, can't this be simplified to `tableTypes[T]['Selectable']`?