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fix(pluginutils): improve regex performance #1753

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merged 1 commit into from
Sep 22, 2024
+3 −3
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fix(pluginutils): improve regex performance #1753

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4 changes: 2 additions & 2 deletions packages/pluginutils/src/attachScopes.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ const attachScopes: AttachScopes = function attachScopes(ast, propertyName = 'sc
const node = n as estree.Node;
// function foo () {...}
// class Foo {...}
if (/(Function|Class)Declaration/.test(node.type)) {
if (/(?:Function|Class)Declaration/.test(node.type)) {
scope.addDeclaration(node, false, false);
}

Expand Down Expand Up @@ -98,7 +98,7 @@ const attachScopes: AttachScopes = function attachScopes(ast, propertyName = 'sc
}

// create new for scope
if (/For(In|Of)?Statement/.test(node.type)) {
if (/For(?:In|Of)?Statement/.test(node.type)) {
newScope = new Scope({
parent: scope,
block: true
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2 changes: 1 addition & 1 deletion packages/pluginutils/src/dataToEsm.ts
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Expand Up @@ -91,7 +91,7 @@ const dataToEsm: DataToEsm = function dataToEsm(data, options = {}) {

let maxUnderbarPrefixLength = 0;
for (const key of Object.keys(data)) {
const underbarPrefixLength = key.match(/^(_+)/)?.[0].length ?? 0;
const underbarPrefixLength = /^(_+)/.exec(key)?.[0].length ?? 0;
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@benmccann benmccann Aug 26, 2024 •
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I would expect here and in the other that perhaps it'd be better to move the regex declaration outside the method declaration so that it doesn't have to be recompiled each method invocation and each iteration of this loop

The same would be true of your other PR as well

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Something I've found over time is that it doesn't necessarily help with perf by hoisting it out. Engines these days are able to optimize it, and in most cases only yield very small gains. This was also discussed at lukeed/polka#210

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the discussion there suggests the one place it matters is in loops, so it might still be worth changing here, but not in the other locations?

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Yeah perhaps we can try that here, but I'd prefer to have a benchmark on that first before making the change though

if (underbarPrefixLength > maxUnderbarPrefixLength) {
maxUnderbarPrefixLength = underbarPrefixLength;
}
Expand Down
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