fix: improve addChild and path performance#1891
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Chriscbr
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Aug 27, 2023
| * Components are separated by '/'. | ||
| */ | ||
| public get path(): string { | ||
| const components = this.scopes.filter(c => c.node.id).map(c => c.node.id); |
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Calling filter generates one array, and calling map after creates another array. It should be slightly faster to create a single array and perform filtering inside a for loop.
| throw new Error(`Cannot add children to "${this.path}" during synthesis`); | ||
| } | ||
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| if (childName in this._children) { |
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From what I tested, array access is slightly faster than using the "in" operator
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| if (!childName && this.id) { | ||
| throw new Error(`cannot add a nameless construct to the named scope: ${this.path}`); | ||
| } |
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I don't think this if branch can get called. Here's my reasoning:
addChildis only called if a non-nullscopeis passed to theNodeconstructor.- if a non-null
scopeis passed to theNodeconstructor, andthis.idhas a falsey value (likeundefinedor an empty string), then an error will be thrown in theNodeconstructor beforeaddChildis called. - based on (1) and (2), when
addChildis called, it's guaranteed thatchildNamewill not be a falsey value - the if statement's body only executes if childName takes on a falsey value
I tried coming up with a test case that would actually throw this error but I don't think there's a way.
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| if (Object.keys(this._children).length > 1 && Object.keys(this._children).filter(x => !x).length > 0) { | ||
| throw new Error('only a single construct is allowed in a scope if it has an empty name'); | ||
| } |
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I also don't think this branch can ever get called. Here was my reasoning:
- From my other comment,
childNamewill never take on a falsey value (like an empty string). - From (1), the line
this._children[childName] = childlcan never add falsey values as keys tothis._children. - There are no other lines of code that add new keys to
this._children. - Therefore,
this._childrenwill always have keys with truthy values, soObject.keys(this._children).filter(x => !x)can never have a length greater than 0.
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Improve the performance of the
constructslibrary by removing several branches in the library's hot paths and switching to some more performant operations.On my laptop, the benchmark I used (shared in a gist here) takes about 5.0-5.3 seconds with the old version of constructs, and about 1.1-1.2 seconds with the new version of constructs.
Misc:
testfolder.npmignoreto reduce the package's npm footprint.