Porting python's 'with' construct to TypeScript
$begingroup$
Now that async generators are available in the platforms I care about, I figured I'd try porting Python's ingenious with construct to JS as a utility. My first stab looks like this:
type Index = string | symbol | number;
function isIndex(obj: any): obj is Index {
return (
typeof obj === 'string' ||
typeof obj === 'symbol' ||
typeof obj === 'number'
);
}
type Disposable<TDisposerKey extends Index> = {
[k in TDisposerKey]: DisposerMethod
};
type DisposerMethod = () => void | Promise<void>;
type DisposerCallback<TDisposable> = (res: TDisposable) => void | Promise<void>;
function using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(resource: TDisposable, key: TDisposerKey): AsyncIterable<TDisposable>;
function using<TDisposable>(
resource: TDisposable,
disposer: DisposerCallback<TDisposable>
): AsyncIterable<TDisposable>;
async function* using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(
resource: TDisposable,
keyOrDisposer: TDisposerKey | DisposerCallback<TDisposable>
): AsyncIterable<TDisposable> {
try {
yield resource;
} finally {
if (typeof keyOrDisposer === 'function') {
await keyOrDisposer(resource);
} else if (isIndex(keyOrDisposer)) {
await resource[keyOrDisposer]();
}
}
}
async function main(): Promise<any> {
for await (const db of using(new PouchDB('zz-data\foo'), 'close')) {
console.dir(await db.info());
return await db.get('qwertyuiop');
}
}
Does anything jump out at anybody? A for..await..of loop with only one iteration is odd, but it's the only way to handle this lexically, and it saves me having to juggle types for a callback-based alternative which was fiddly to make generic. The overloads are also a mouthful, but that's TS for you.
async-await typescript
edited 4 mins ago
200_success
129k15153415
asked 11 hours ago
millimoosemillimoose
29527
$endgroup$
add a comment |
$begingroup$
Now that async generators are available in the platforms I care about, I figured I'd try porting Python's ingenious with construct to JS as a utility. My first stab looks like this:
type Index = string | symbol | number;
function isIndex(obj: any): obj is Index {
return (
typeof obj === 'string' ||
typeof obj === 'symbol' ||
typeof obj === 'number'
);
}
type Disposable<TDisposerKey extends Index> = {
[k in TDisposerKey]: DisposerMethod
};
type DisposerMethod = () => void | Promise<void>;
type DisposerCallback<TDisposable> = (res: TDisposable) => void | Promise<void>;
function using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(resource: TDisposable, key: TDisposerKey): AsyncIterable<TDisposable>;
function using<TDisposable>(
resource: TDisposable,
disposer: DisposerCallback<TDisposable>
): AsyncIterable<TDisposable>;
async function* using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(
resource: TDisposable,
keyOrDisposer: TDisposerKey | DisposerCallback<TDisposable>
): AsyncIterable<TDisposable> {
try {
yield resource;
} finally {
if (typeof keyOrDisposer === 'function') {
await keyOrDisposer(resource);
} else if (isIndex(keyOrDisposer)) {
await resource[keyOrDisposer]();
}
}
}
async function main(): Promise<any> {
for await (const db of using(new PouchDB('zz-data\foo'), 'close')) {
console.dir(await db.info());
return await db.get('qwertyuiop');
}
}
Does anything jump out at anybody? A for..await..of loop with only one iteration is odd, but it's the only way to handle this lexically, and it saves me having to juggle types for a callback-based alternative which was fiddly to make generic. The overloads are also a mouthful, but that's TS for you.
async-await typescript
edited 4 mins ago
200_success
129k15153415
asked 11 hours ago
millimoosemillimoose
29527
$endgroup$
add a comment |
$begingroup$
Now that async generators are available in the platforms I care about, I figured I'd try porting Python's ingenious with construct to JS as a utility. My first stab looks like this:
type Index = string | symbol | number;
function isIndex(obj: any): obj is Index {
return (
typeof obj === 'string' ||
typeof obj === 'symbol' ||
typeof obj === 'number'
);
}
type Disposable<TDisposerKey extends Index> = {
[k in TDisposerKey]: DisposerMethod
};
type DisposerMethod = () => void | Promise<void>;
type DisposerCallback<TDisposable> = (res: TDisposable) => void | Promise<void>;
function using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(resource: TDisposable, key: TDisposerKey): AsyncIterable<TDisposable>;
function using<TDisposable>(
resource: TDisposable,
disposer: DisposerCallback<TDisposable>
): AsyncIterable<TDisposable>;
async function* using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(
resource: TDisposable,
keyOrDisposer: TDisposerKey | DisposerCallback<TDisposable>
): AsyncIterable<TDisposable> {
try {
yield resource;
} finally {
if (typeof keyOrDisposer === 'function') {
await keyOrDisposer(resource);
} else if (isIndex(keyOrDisposer)) {
await resource[keyOrDisposer]();
}
}
}
async function main(): Promise<any> {
for await (const db of using(new PouchDB('zz-data\foo'), 'close')) {
console.dir(await db.info());
return await db.get('qwertyuiop');
}
}
Does anything jump out at anybody? A for..await..of loop with only one iteration is odd, but it's the only way to handle this lexically, and it saves me having to juggle types for a callback-based alternative which was fiddly to make generic. The overloads are also a mouthful, but that's TS for you.
async-await typescript
edited 4 mins ago
200_success
129k15153415
asked 11 hours ago
millimoosemillimoose
29527
$endgroup$
Now that async generators are available in the platforms I care about, I figured I'd try porting Python's ingenious with construct to JS as a utility. My first stab looks like this:
type Index = string | symbol | number;
function isIndex(obj: any): obj is Index {
return (
typeof obj === 'string' ||
typeof obj === 'symbol' ||
typeof obj === 'number'
);
}
type Disposable<TDisposerKey extends Index> = {
[k in TDisposerKey]: DisposerMethod
};
type DisposerMethod = () => void | Promise<void>;
type DisposerCallback<TDisposable> = (res: TDisposable) => void | Promise<void>;
function using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(resource: TDisposable, key: TDisposerKey): AsyncIterable<TDisposable>;
function using<TDisposable>(
resource: TDisposable,
disposer: DisposerCallback<TDisposable>
): AsyncIterable<TDisposable>;
async function* using<
TDisposerKey extends Index,
TDisposable extends Disposable<TDisposerKey>
>(
resource: TDisposable,
keyOrDisposer: TDisposerKey | DisposerCallback<TDisposable>
): AsyncIterable<TDisposable> {
try {
yield resource;
} finally {
if (typeof keyOrDisposer === 'function') {
await keyOrDisposer(resource);
} else if (isIndex(keyOrDisposer)) {
await resource[keyOrDisposer]();
}
}
}
async function main(): Promise<any> {
for await (const db of using(new PouchDB('zz-data\foo'), 'close')) {
console.dir(await db.info());
return await db.get('qwertyuiop');
}
}
Does anything jump out at anybody? A for..await..of loop with only one iteration is odd, but it's the only way to handle this lexically, and it saves me having to juggle types for a callback-based alternative which was fiddly to make generic. The overloads are also a mouthful, but that's TS for you.
async-await typescript
async-await typescript
edited 4 mins ago
200_success
129k15153415
asked 11 hours ago
millimoosemillimoose
29527
edited 4 mins ago
200_success
129k15153415
asked 11 hours ago
millimoosemillimoose
29527
edited 4 mins ago
200_success
129k15153415
edited 4 mins ago
200_success
129k15153415
edited 4 mins ago
200_success
129k15153415
129k15153415
asked 11 hours ago
millimoosemillimoose
29527
asked 11 hours ago
millimoosemillimoose
29527
asked 11 hours ago
millimoosemillimoose
29527
29527
add a comment |
add a comment |
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