any禁止絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

BOZېࢭ
ઈରʹܕ෇͚ΛఘΊͳ͍ͨΊͷ
ศརͳϢʔςΟ
ϦςΟؔ਺
/PW TUBOEGN5&$)45"/%5ZQF4DSJQU
!PLVOPLFOUBSP

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୭
w Ԟ໺ݡଠ࿠!PLVOPLFOUBSP
w ΫϨε΢ΣΞגࣜձࣾ
w 5ZQF4DSJQUྺ೥

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ܕɺ
ͪΌΜͱ෇͚ͯ·͔͢
const res = await fetch('/api/users', {method: 'GET'});

const users = await res.json();

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͜ΕͰຬ଍ͯ͠ͳ͍
ʁ
const res = await fetch('/api/users', {method: 'GET'});

const users = await res.json() as User[];

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anyܕʹas TΛࢦఆ͢Δͷ͸ةݥ
wʮanyܕ͸ةݥʯ
 
ʜͱ͍͏࿩୊͸ཧղ͍ͯͯ͠΋ɺ
as TͳΒฏؾͰ࢖ͬͯ͠·
͏ݱ৔͸গͳ͘ͳ͍
w Ͱ΋
ʮany as T΋ةݥʯ

w anyܕͷ஋ʹas T
ʢas User[]ͳͲʣ
Λ෇͚ͯ΋ίϯύΠϧΤϥʔʹͳΒͳ͍

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ͳʹ͕ةݥͳͷ͔
w ͍͘
ΒͰ΋ӕ͕͚ͭΔ
w ίϯύΠϧ͸௨͍ͬͯͯ΋ɺ
࣮ࡍʹͦ͜ʹྲྀΕͯ͘
Δ஋ͷߏ଄͸ҟͳΔঢ়گ
w as T͸
ʮίϯύΠ
ϥΛ͍͍ٗͯΔ͚ͩʯ
Ͱ͋Δ

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͜ͷίʔ
υ͸ΤϥʔʹͳΒͳ͍
const res1 = await fetch('/api/users', {method: 'GET'});

const users = await res1.json() as User[];

const res2 = await fetch('/api/items', {method: 'GET'});

const items = await res2.json() as User[];
as Item[] Ͱ͸ʁʁ

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asΛ࢖Θͣ҆શʹܕ෇͚Λ͢Δ
w anyېࢭasېࢭ
w 5ZQFQSFEJDBUFTΛ࢖͏
 
IUUQTXXXUZQFTDSJQUMBOHPSHEPDTIBOECPPLOBSSPXJOHIUNMVTJOHUZQFQSFEJDBUFT

w function isSomething(v: unknown): v is Something { ...
 
Έ͍ͨͳ΍ͭ
w JG৚݅ࣜʹͯisSomething(v)Λ࢖ͬͨΒɺ
 
ͦͷJGϒϩοΫ಺Ͱ͸v͕Somethingܕͱͯ͠ѻ͑Δ

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type User = {

id: number;

name: string;

};

function hasId(v: unknown): v is { id: unknown } {

if (typeof v !== "object" || v === null) {

return false;

}

return "id" in v;

}

function hasName(v: unknown): v is { name: unknown } {


return false;

}

return "name" in v;

}

function isUser(v: unknown): v is User {

if (!hasId(v) || !hasName(v)) {

return false;

}

if (typeof v.id !== "number") {

return false;

}

if (typeof v.name !== "string") {

return false;

}

return true;

}

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ׂͱखؒ
w asΛઈ໓ͤ͞Α
͏
ͱͨ͠Βɺ
5ZQFQSFEJDBUFTؔ਺͕ͨ͘
͞Μඞཁ
w JGϒϩοΫͷதͰ͔͠ਪ࿦͞Εͳ͍ͷͰɺ
ίʔ
υ͕ෳࡶʹͳΓ͕ͪ
w JGϒϩοΫ͕ඞਢͳͷ͸໘౗

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JGจΛ࢖Θͳ͍
w "TTFSUJPOGVODUJPOTΛ࢖͏
 
IUUQTXXXUZQFTDSJQUMBOHPSHEPDTIBOECPPLSFMFBTFOPUFTUZQFTDSJQUIUNMBTTFSUJPOGVODUJPOT

w function assertSomething(
 
v: unknown): asserts v is Something { ...
 
Έ͍ͨͳ΍ͭ
w assertSomething(v)Λ࢖ͬͨΒɺ
ͦͷؔ਺͕ྫ֎Λ౤͛ͳ͍ݶΓ
 
ಉҰείʔϓͷҎ߱ͷεςʔ
τϝϯ
τͰ͸v͕Somethingܕͱͯ͠ѻ͑Δ

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type User = {

id: number;

name: string;

};

function assertId(v: unknown): asserts v is { id: unknown } {


throw new Error("Value should be non-null object");

}

if (!("id" in v)) {

throw new Error('Value should have the property "id"');

}

// noop

}

function assertName(v: unknown): asserts v is { name: unknown } {


throw new Error("Value should be non-null object");

}

if (!("name" in v)) {

throw new Error('Value should have the property "name"');

}

// noop

}

function assertUser(v: unknown): asserts v is User {

assertId(v);

assertName(v);

if (typeof v.id !== "number") {

throw new Error('"id" should be a number');

}

if (typeof v.name !== "string") {

throw new Error('"name" should be a string');

}

// noop

}

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΍ͬͺΓखؒ
w asΛઈ໓ͤ͞ΔͨΊʹ͜͜·Ͱ͢Δ
ʁ

w ҰͭͷΦϒδΣΫ
τʹ͍ͭͯݕূ͢Δ͚ͩͰؔ਺ଟ͗͢͡Όͳ͍
ʁ

w ΋͏asΛ࢖ͬͯ΋͍͍Μ͡Όʜ
ʁ

w ઈରʹఘΊͳ͍

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ศརؔ਺Λ࡞ͬͯΈͨ
w ϓϩύςΟ͕ੜ͍͑ͯΔ͜ͱΛϥϯλΠϜͰݕূͭͭ͠
w ܕ΋ͪΌΜͱ෇͍ͯ͘Εͯ
w ͔͠΋ܕఆٛΛमਖ਼ͨ͠ΒϥϯλΠϜͰ
 
ݕূ͞ΕΔϓϩύςΟ
΋௥ैͯ͠΄͍͠

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type UnionToIntersection = (U extends any ? (k: U) => void : never) extends (

k: infer I

) => void

? I

: never;

type LastOf = UnionToIntersection<

T extends any ? () => T : never

> extends () => infer R

? R

: never;

type Push = [...T, V];

type UnionToTuple<

T,

L = LastOf,

N = [T] extends [never] ? true : false

> = true extends N ? [] : Push>, L>;

type Tuple = [TItem, ...TItem[]] & {

length: TLength;

};

/**

* Tuple ͸ [string, string, string] Λฦ͢

* ͦΕΛԠ༻ͯ͠ 'a' | 'b' Λ ['a' | 'b', 'a' | 'b'] ʹ͢Δ

*

* 'a' | 'b'

* => ['a' | 'b', 'a' | 'b']

* 'a' | 'b' | 'c'

* => ['a' | 'b' | 'c', 'a' | 'b' | 'c', 'a' | 'b' | 'c']

*/

type UnionToUnionTuple = Tuple["length"]>;

type TypeEq = (() => T extends A ? 1 : 2) extends () => T extends B

? 1

: 2

? true

: false;

type RemoveNeverProperties = Pick<

T,

{

[P in keyof T]: [T[P]] extends [never] ? never : P;

}[keyof T]

>;

type AnyAs0 = {

[P in keyof T]: TypeEq extends true ? 0 : T[P];

};

type UnknownAs0 = {


};

type OptionalAsUndefined = {

[P in keyof T]: T[P] extends NonNullable ? T[P] : undefined;

};

type UndefinedAsNever = {

[P in keyof T]-?: T[P] extends undefined ? never : T[P];

};

/**

* { a?: string; b: number; c?: any; d: any } Λ

* { b: number; d: any } ͚ͩʹ͢Δɻ

*

* AnyAs0 ͕ͳ͍ͱ ?: any ΁ͷରԠ͕࿙ΕΔͷͰ஫ҙɻ

*/

type RemoveOptionalProperties = {

[P in keyof RemoveNeverProperties<

UndefinedAsNever>>>

>]: T[P];

};

function isObject(v: unknown): v is Record {

if (typeof v !== "object") {

return false;

}

return v !== null;

}

function assertObject(

v: unknown,

target = ""

): asserts v is Record {

if (!isObject(v)) {

throw new Error(`${target} should be object`.trim());

}

}

function isMatchedType(

v: unknown,

props: UnionToUnionTuple>,

errorPropsRef: string[],

target = ""

): v is T {

assertObject(v, target);

if (new Set(props).size !== props.length) {

throw new Error("Invalid props");

}

return props

.map((prop) => {

if (typeof prop !== "string") {

throw new Error("Invalid prop");

}

const within = prop in v;

if (!within) {

errorPropsRef.push(prop); // mutate

}

return within;

})

.every((flag) => flag);

}

export function assertMatchedType(

v: unknown,


target = ""

): asserts v is T {

const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর

if (!isMatchedType(v, props, errorPropsRef, target)) {

// ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ

throw new Error(

`${target} should be aligned type. ${

0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : ""

}`.trim()

);

}

}

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.map((prop) => {



}


if (!within) {


}

return within;

})


}


v: unknown,


target = ""

): asserts v is T {




throw new Error(



}`.trim()

);

}

}

ͳʹΛ࡞͔ͬͨ
w assertMatchedType()ؔ਺Λ࣮૷ͨ͠
w ୈҾ਺ʹݕূ͍ͨ͠ΦϒδΣΫ
τ
w ୈҾ਺ʹݕূ͍ͨ͠ϓϩύςΟ໊ͷ഑ྻ
w ܕύϥϝʔλʹཧ૝ͷܕఆٛΛॻ͘

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.map((prop) => {



}


if (!within) {


}

return within;

})


}


v: unknown,


target = ""

): asserts v is T {




throw new Error(



}`.trim()

);

}

}

ͳʹΛ࡞͔ͬͨ
w assertMatchedType()ؔ਺Λ࣮૷ͨ͠
w ୈҾ਺ʹݕূ͍ͨ͠ΦϒδΣΫ
τ
w ୈҾ਺ʹݕূ͍ͨ͠ϓϩύςΟ໊ͷ഑ྻ
w ܕύϥϝʔλʹཧ૝ͷܕఆٛΛॻ͘
type User = {

id: number;

name: string;

};

const obj: unknown = { id: 1, name: "foo" };

assertMatchedType(obj, ["id", "name"]);

console.log(obj);

View Slide

.map((prop) => {



}


if (!within) {


}

return within;

})


}


v: unknown,


target = ""

): asserts v is T {




throw new Error(



}`.trim()

);

}

}

ศརͳͱ͜Ζ
w ܕఆ͕ٛมΘΔͱɺ
ୈҾ਺ͰٻΊΒΕΔ
 
Ҿ਺ͷܕ͕มΘΔ
w ܕఆ͚ٛͩ௚ͯ͠ɺ
 
ϥϯλΠϜଆ͕௚ͬͯͳ͍ঢ়گΛ๷͙
type User = {

id: number;

name: string;

email: string;

};



console.log(obj);
Argument of type '["id", "name"]' is not assignable to
parameter of type 'UnionToUnionTuple<"id" | "name" |
"email">'.

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v: unknown,

target = ""


if (!isObject(v)) {


}

}


v: unknown,



target = ""

): v is T {




}

return props

.map((prop) => {



}


if (!within) {


}

return within;

})


}


v: unknown,


target = ""

): asserts v is T {


w ศརؔ਺ΛassertObject()Λࣄલʹ
 
࡞͓ͬͯ͘
w ϓϩύςΟࢦఆ͸͢΂ͯϢχʔΫͰ͋Δ͜ͱΛ
 
อূ
w ͻͱͭͻͱͭinΛ࢖ͬͯ֬ೝ
w ͳ͚Ε͹Τϥʔࢀরʹه࿥
ϥϯλΠϜଆͷ࢓૊Έ

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*


*/



UndefinedAsNever>>>

>]: T[P];

};


if (typeof v !== "object") {

return false;

}

return v !== null;

}


v: unknown,

target = ""


if (!isObject(v)) {


}

}


v: unknown,



target = ""

): v is T {




}

return props

.map((prop) => {

w ศརؔ਺assertObject()͸
 
"TTFSUJPOGVODUJPOTͷ
 
͓खຊͷΑ
͏ͳؔ਺
assertObject()

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w ͔͜͜Β5ZQF4DSJQUͷຊؾ
w ͢΂ͯͷϓϩύςΟ
Λྻڍ͍ͨ͠
w PQUJPOBMͳϓϩύςΟ͸ݕূͨ͘͠ͳ͍
w PQUJPOBMͳϓϩύςΟ͸ॻ͔ͳ͘
ͯ΋
 
ίϯύΠϧΤϥʔʹͨ͘͠ͳ͍
w ͦΕΛ͢ΔͨΊͷܕύζϧ
ܕύζϧ

: false;


T,

{


}[keyof T]

>;

type AnyAs0 = {


};

type UnknownAs0 = {


};



};



};

/**



*


*/



UndefinedAsNever>>>

>]: T[P];

};


View Slide

: false;


T,

{


}[keyof T]

>;

type AnyAs0 = {


};

type UnknownAs0 = {


};



};



};

/**



*


*/



UndefinedAsNever>>>

>]: T[P];

};


Ṗͷຐ๏
w AnyAs0ͱUnknownAs0Ͱɺ
anyܕͱ
 
unknownܕΛҰ୴͢΂ͯ
 
0ܕ
ʢ਺஋Ϧςϥϧܕʣ
ʹஔ͖׵͑Δ
w PQUJPOBMͰ͋Ε͹
 
͢΂ͯundefinedʹ͢Δ
w 0ܕʹஔ͖׵͓͔͑ͯͳ͍ͱ
 
PQUJPOBManyͱPQUJPOBMunknown͕
 
ਖ਼͘͠ॲཧ͞Εͳ͍

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: false;


T,

{


}[keyof T]

>;

type AnyAs0 = {


};

type UnknownAs0 = {


};



};



};

/**



*


*/



UndefinedAsNever>>>

>]: T[P];

};


Ṗͷຐ๏
w undefinedΛ͢΂ͯPQUJPOBMΛ֎ͭͭ͠
 
neverʹஔ͖׵͑Δ
w neverͰ͋Ε͹ɺ
ͦΕΒΛ͢΂ͯ
 
PickΛ࢖ͬͯআڈ͢Δ
w ͜Ε͸undefinedΛؚΊଞͷܕͰ͸
 
͜ͷΑ
͏ͳॲཧ͕࣮ݱͰ͖ͣ
 
neverͷΈআڈͰ͖Δ

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ܕύζϧͷ൪ਓ
w ܕύζϧΛॻ͍͍ͯΔͱ͖͸ݕূ͕ࠔ೉
w TypeEqʻA, BʼΛ࢖ͬͯ
 
ܕςε
τΛॻ͘
ͱΑ͍
w AnyAs0 UnknownAs0Ͱ΋࢖༻


length: TLength;

};

/**


* ͦΕΛԠ༻ͯ͠ 'a' | 'b' Λ ['a' | 'b', 'a' | 'b'] ʹ͢Δ

*

* 'a' | 'b'

* => ['a' | 'b', 'a' | 'b']

* 'a' | 'b' | 'c'

* => ['a' | 'b' | 'c', 'a' | 'b' | 'c', 'a' | 'b' | 'c']

*/


type TypeEq = (() => T extends A ? 1 : 2) extends () => T extends B

? 1

: 2

? true

: false;


T,

{


}[keyof T]

>;

type AnyAs0 = {


};

type UnknownAs0 = {


};


https://qiita.com/kgtkr/items/2a8290d1b1314063a524

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type UnionToIntersection = (U extends any ? (k: U) => void : never) extends (

k: infer I

) => void

? I

: never;

type LastOf = UnionToIntersection<

T extends any ? () => T : never

> extends () => infer R

? R

: never;

type Push = [...T, V];

type UnionToTuple<

T,

L = LastOf,

N = [T] extends [never] ? true : false



length: TLength;

};

/**


* ͦΕΛԠ༻ͯ͠ 'a' | 'b' Λ ['a' | 'b', 'a' | 'b'] ʹ͢Δ

*

* 'a' | 'b'

* => ['a' | 'b', 'a' | 'b']

* 'a' | 'b' | 'c'

* => ['a' | 'b' | 'c', 'a' | 'b' | 'c', 'a' | 'b' | 'c']

*/


Ṗͷຐ๏
w PQUJPOBMͳϓϩύςΟ
Λ͢΂ͯ
 
আڈͨ͠ͷͰɺ
࢒ΓͷඞਢϓϩύςΟ
Λ
 
ྻڍ͠λϓϧͰड͚औΓ͍ͨ
w UnionToTupleΛ࢖͑͹keyof Tͷ
 
݁ՌΛλϓϧͱͯ͠ѻ͑Δ
w ͔͠͠ॱෆಉͰ͋Δ
ʢఆ͕ٛهड़ॱʹ
 
ͳΒͳ͍ʣ
͜ͱͰ௚ײతͰ͸ͳ͍ͨΊ
 
UnionToUnionTupleͰهड़ॱΛ
 
ࣗ༝ʹ͢Δ
w ϥϯλΠϜͰnew Set()Λͨ͠ͷ͸
 
͜Εରࡦ

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͜Ε͕࣮ݱͰ͖Δ
w ܕఆ͕ٛมΘΔͱɺ
ୈҾ਺ͰٻΊΒΕΔ
 
Ҿ਺ͷܕ͕มΘΔ
w ܕఆ͚ٛͩ௚ͯ͠ɺ
 
ϥϯλΠϜଆ͕௚ͬͯͳ͍ঢ়گΛ๷͙

.map((prop) => {



}


if (!within) {


}

return within;

})


}


v: unknown,


target = ""

): asserts v is T {




throw new Error(



}`.trim()

);

}

}

type User = {

id: number;

name: string;

email: string;

};



console.log(obj);
Argument of type '["id", "name"]' is not assignable to
parameter of type 'UnionToUnionTuple<"id" | "name" |
"email">'.

View Slide

.map((prop) => {



}


if (!within) {


}

return within;

})


}


v: unknown,


target = ""

): asserts v is T {




throw new Error(



}`.trim()

);

}

}

࿙Εʹ͍ͭͯ
w id͕number name͕stringͰ͋Δ͜ͱ
 
·Ͱ͸Έͯ͘Εͳ͍
w Α
Γ҆શʹ͍ͨ͠ͳΒ͢΂ͯͷϓϩύςΟͷܕΛ
 
unknownܕʹ͢Δͷ͕Α͍
w ͦͷ৔߹͸assertString()
assertNumber()ͳͲͷؔ਺ͱ૊Έ߹ΘͤΔ
type User = {

id: unknown;

name: unknown;

email: unknown;

};



console.log(obj);

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$POEJUJPOBM5ZQFTΛۃΊΔͱָ͍͠
w $POEJUJPOBM5ZQFT͸࣮͸͔ͳΓͷදݱྗ͕͋Δ
 
IUUQTXXXUZQFTDSJQUMBOHPSHEPDTIBOECPPLDPOEJUJPOBMUZQFTIUNM

w Ұݟݫͦ͠͏ͳܕਪ࿦Ͱ΋࣮͸ॻ͚ͨΓ͢Δ
w $POEJUJPOBM5ZQFTΛۃΊΑ
͏
w as͸ېࢭͰ͖Δ

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5IBOLZPV
https://gist.github.com/okunokentaro/74361c2683bd8e0f349d21ddebe189cf

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any禁止絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

any禁止絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

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any禁止 絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

any禁止 絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

OKUNOKENTARO

More Decks by OKUNOKENTARO

Other Decks in Technology

Featured

Transcript

any禁止絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

any禁止絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6