GeezerVison is showing github.com — Refactoring to convert && chain to optional chain expression · Issue #35018 · microsoft/TypeScript
Refactoring to convert && chain to optional chain expression #35018Descriptioninterface Foo {
bar?: {
baz?: string;
}
}
declare let foo: Foo | undefined;
[|foo && foo.bar && foo.bar.baz|]It should be possible to convert that chain into the following:
interface Foo {
bar?: {
baz?: string;
}
}
declare let foo: Foo | undefined;
foo?.bar?.baz;Reacted by Bruce Pascoe, Eden Turgeman, Nico Jansen, Borui Gu, Ismail Ghallou , Mattias Buelens, Jeroen Meijer (Jay), Justin Grant, harrisoncarter, Gabriel Francisco and 16 more Reacted by AnyhowStep, Michał Gołębiowski-Owczarek, Matt Kane, Matija Grcic, Jiri Spac, Steven, Orta Therox, Andrii Byk, Dustin Savery, Eden Turgeman and 18 more ActivityDanielRosenwasser commented on Nov 9, 2019 You know, mostly like this
Reacted by Matija Grcic, Jiri Spac, Steven, Nico Jansen, Alex Quintero, Ismail Ghallou , Bruno Antunes, ExE Boss, Luciano Lima, Abhishek Datta and 6 more Reacted by Bruno Antunes, Michael Loughry, Mohit Mayank, Luciano Lima, Abhishek Datta, Roger Padilla, Ali Taheri Moghaddar and AwesomeObserver Urigo commented on Nov 9, 2019 maybe a code-mode or babel transform that runs throughout a codebase? DanielRosenwasser commented on Nov 9, 2019 Uri Goldshtein (@Urigo) That could be done too, but I think having this granularity is good because it's not strictly the same semantics. ?. always returns undefined, && keeps the original nullish value. switz commented on Nov 10, 2019 Also keep in mind that optional chaining returns true on 0 and '' (empty string), normally falsy values in javascript. So running this as a code mod would almost certainly cause unintended bugs. Reacted by Nico Jansen, Kristiqn Tachev, Johan Faerch, Justin Grant, Max Schmitt, Carlos Abbate, Ian Copp, Josef and Ali Taheri Moghaddar MLoughry commented on Nov 11, 2019
Also keep in mind that optional chaining returns true on 0 and '' (empty string), normally falsy values in javascript. So running this as a code mod would almost certainly cause unintended bugs.
I'm not sure I really follow. Such code would be rather questionable in the first place, no? If you have an && chain that could be converted to an optional chain, and it returns '' or false as a short-circuit, then the same code would be throwing a TypeError if the value is a non-empty string or true. fatcerberus commented on Nov 12, 2019 I could certainly envision a scenario where code was written that depends on short-circuiting on falsy values. We're eternally stuck with typeof null === 'object' for backward compatibility reasons, after all.
Also there's no TypeError because boolean and string are object-coercible. The subsequent property access would just return undefined and short-circuit. jineshshah36 commented on Nov 17, 2019 [|foo && foo.bar && foo.bar.baz|]
What do the “|” mean? dragomirtitian commented on Nov 18, 2019 Jinesh Shah (@jineshshah36) [|code|] is the syntax used typescript four-slash tests to mark a selection. Some diagnostic suggestions are not exposed unless they can be applied to the selected code. Reacted by Jinesh Shah and ExE Boss MrAndersen1 commented on Dec 9, 2019 All too eager to start using the ?. syntax I managed to play a trick on myself by converting
if (foo && foo.bar && foo.bar.indexOf(someValue) !== -1)
to
if (foo?.bar?.indexOf(someValue) !== -1)
which had quite the opposite behaviour of what was intended heh.
Just one of the (probably more obvious in hindsight) things a script would have to keep in mind :) changed the title [-]Convert && chain to optional chain expression[/-] [+]Refactoring to convert && chain to optional chain expression[/+] on Apr 22, 2020DanielRosenwasser commented on May 5, 2020 There's a question of whether or not nullish coalescing (??) should be supported here as part of the code action. DanielRosenwasser commented on May 5, 2020 Also, what the supported patterns are:
| Category |
Input |
Output |
Comments |
&& property chains: |
a && a.b.c && a.b.c.d |
a?.b.c?.d |
|
| Ternary checks with property access |
a.b ? a.b.c : "hello" |
a.b?.c ?? "hello" |
Is this one type-driven? What if c is string | null? |
&& property/call chains: |
a && a.b.c && a.b.c() |
a?.b.c?.() |
|
Kingwl commented on May 13, 2020 Ahhhh, i have some existed work about this. And I'm happy to port here kylemh commented on May 13, 2020 I’m not sure of the viability of going after library refactorings (as opposed to just JS -> TS), but I think one huge win would be if TS could automatically refactor lodash/get usages and/or ramda/pathOr usages. Kingwl commented on May 13, 2020
if TS could automatically refactor lodash/get usages and/or ramda/pathOr usages.
Good idea. IMO TypeScript cannot provide that but there's outside tools.
eg: https://github.com/HearTao/ts-upgrade Reacted by Kyle Holmberg, ZHAO Jin-Xiang and Ebuall Kingwl commented on May 20, 2020 Are there any existed tools or algorithms to compare expression and judge they are equality?
I have some ugly work about it but they cannot work well.
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