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setImmutably: don't clone all objects #56612

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merged 5 commits into from
Nov 30, 2023
Merged

setImmutably: don't clone all objects #56612

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343e776
setImmutably: don't clone all objects
ellatrix Nov 28, 2023
fb0c234
Clearer var name
ellatrix Nov 28, 2023
b3a2b14
Maybe don't throw :P
ellatrix Nov 28, 2023
7bdcfd0
setImmutably: same but with no recursion
mcsf Nov 29, 2023
818ee03
Simplify
ellatrix Nov 29, 2023
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76 changes: 12 additions & 64 deletions packages/block-editor/src/utils/object.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,27 +4,6 @@
import { paramCase } from 'change-case';
import memoize from 'memize';

/**
* Converts a path to an array of its fragments.
* Supports strings, numbers and arrays:
*
* 'foo' => [ 'foo' ]
* 2 => [ '2' ]
* [ 'foo', 'bar' ] => [ 'foo', 'bar' ]
*
* @param {string|number|Array} path Path
* @return {Array} Normalized path.
*/
function normalizePath( path ) {
if ( Array.isArray( path ) ) {
return path;
} else if ( typeof path === 'number' ) {
return [ path.toString() ];
}

return [ path ];
}

/**
* Converts any string to kebab case.
* Backwards compatible with Lodash's `_.kebabCase()`.
Expand Down Expand Up @@ -55,33 +34,6 @@ export function kebabCase( str ) {
} );
}

/**
* Clones an object.
* Arrays are also cloned as arrays.
* Non-object values are returned unchanged.
*
* @param {*} object Object to clone.
* @return {*} Cloned object, or original literal non-object value.
*/
function cloneObject( object ) {
if ( Array.isArray( object ) ) {
return object.map( cloneObject );
}

if ( object && typeof object === 'object' ) {
return {
...Object.fromEntries(
Object.entries( object ).map( ( [ key, value ] ) => [
key,
cloneObject( value ),
] )
),
};
}

return object;
}

/**
* Immutably sets a value inside an object. Like `lodash#set`, but returning a
* new object. Treats nullish initial values as empty objects. Clones any
Expand All @@ -93,24 +45,20 @@ function cloneObject( object ) {
* @return {Object} Cloned object with the new value set.
*/
export function setImmutably( object, path, value ) {
const normalizedPath = normalizePath( path );
const newObject = object ? cloneObject( object ) : {};
path = Array.isArray( path ) ? path : [ path ];
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Should we use a new constant here? Mutation can introduce potential issues as we refactor in the future, and storing in a new constant is cheap.

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It's not mutatating in this case, just reassigning

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Furthermore, I see we're ditching the numeric path support, and I confirm that this is fine. I can't think of a use case where it won't work properly without that specific handling that we used to do.


if ( path.length === 0 ) {
return value;
}

const shallowClone = Array.isArray( object )
? [ ...object ]
: { ...object };
const [ first, ...rest ] = path;

normalizedPath.reduce( ( acc, key, i ) => {
if ( acc[ key ] === undefined ) {
if ( Number.isInteger( path[ i + 1 ] ) ) {
acc[ key ] = [];
} else {
acc[ key ] = {};
}
}
if ( i === normalizedPath.length - 1 ) {
acc[ key ] = value;
}
return acc[ key ];
}, newObject );
shallowClone[ first ] = setImmutably( shallowClone[ first ], rest, value );
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Is there a way to achieve the same without recursivity? I think recursivity has a performance overhead that is best avoided in low level functions that get called often.

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Unlike cloneObjects, which was using a recursive function in for every object inside, this one is only called for every item in the path though. But I can check.

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ChatGPT gave me this, is that equivalent :P

export function setImmutably(object, path, value) {
  path = Array.isArray(path) ? path : [path];

  if (path.length === 0) {
    return value;
  }

  const shallowClone = Array.isArray(object)
    ? [...object]
    : { ...object };
  let currentObj = shallowClone;

  for (let i = 0; i < path.length - 1; i++) {
    const key = path[i];
    currentObj = currentObj[key] && typeof currentObj[key] === 'object'
      ? { ...currentObj[key] }
      : {};
    currentObj[key] = currentObj;
  }

  currentObj[path[path.length - 1]] = value;

  return shallowClone;
}

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I'm guessing it's wrong for nested arrays.

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The for loop is weird, it should be

	 for ( let i = 0; i < path.length - 1; i++ ) {
		const key = path[ i ];
		currentObj[ key ] = Array.isArray( currentObj[ key ] )
			? [ ...currentObj[ key ] ]
			: { ...currentObj[ key ] };
		currentObj = currentObj[ key ];
	}

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The number of nested functions = path.length. Even if you'd do something like a forEach or reduce loop you'd have the same number of nested function. It really seems ok to me. We're not deep cloning here.

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non-tail-recursive

yes, this is the main thing for me. I agree that it's harder to read and for this particular use-case, it might not be much recursivity (path is short in most cases), so I'm fine shipping this but I think in JavaScript specifically, it's best to avoid recursion. functions arguments get copied over and over again from caller to callee... and same for return values.

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I spent some time looking at the original code and it used to do:

_.setWith( object ? _.clone( object ) : {}, path, value, _.clone )

That means that we indeed did only a shallow clone, and then a deep clone at the specified path.

Thanks for locating this discrepancy, it seems like we were way more opportunistic when we did the migration.

My take on the recursion approach here is that it will still be better than what we had before - always deep cloning the entire input object. I also find it quite more readable than the loop alternative.

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Pushed 7bdcfd0

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I tweaked it even further after that, I think it makes it more readable and avoids the if statement. Also cached prev[ key ]. Anyway at this point we're probably micro optimising for performance and readability. :)


return newObject;
return shallowClone;
}

const stringToPath = memoize( ( path ) => path.split( '.' ) );
Expand Down
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