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core(legacy-javascript): detect es-shims polyfills #15738

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Jan 12, 2024
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15 changes: 13 additions & 2 deletions core/audits/byte-efficiency/legacy-javascript.js
Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,12 @@ class LegacyJavascript extends ByteEfficiencyAudit {
// Object.defineProperty(String.prototype, 'startsWith'
expression += `|defineProperty\\(${object || 'window'},\\s?${qt(property)}`;

// es-shims
// no(Object,{entries:r},{entries:function
if (object) {
expression += `|\\(${object},\\s*{${property}:.*},\\s*{${property}`;
}

// core-js
if (object) {
const objectWithoutPrototype = object.replace('.prototype', '');
Expand Down Expand Up @@ -234,6 +240,9 @@ class LegacyJavascript extends ByteEfficiencyAudit {
];

for (const [name, coreJs2Module] of coreJsPolyfills) {
// es-shims follows a pattern for its packages.
// Tack it onto the corejs size estimation, as it is likely close in size.
const esShimModule = name.toLowerCase();
data.push({
name,
modules: [
Expand All @@ -243,6 +252,7 @@ class LegacyJavascript extends ByteEfficiencyAudit {
.replace('es6.', 'es.')
.replace('es7.', 'es.')
.replace('typed.', 'typed-array.'),
esShimModule,
],
corejs: true,
});
Expand Down Expand Up @@ -333,8 +343,9 @@ class LegacyJavascript extends ByteEfficiencyAudit {
// Skip if the pattern matching found a match for this polyfill.
if (matches.some(m => m.name === name)) continue;

const source = bundle.rawMap.sources.find(source =>
modules.some(module => source.endsWith(`${module}.js`)));
const source = bundle.rawMap.sources.find(source => modules.some(module => {
return source.endsWith(`/${module}.js`) || source.includes(`node_modules/${module}/`);
}));
if (!source) continue;

const mapping = bundle.map.mappings().find(m => m.sourceURL === source);
Expand Down
20 changes: 18 additions & 2 deletions core/test/audits/byte-efficiency/legacy-javascript-test.js
Original file line number Diff line number Diff line change
Expand Up @@ -176,6 +176,9 @@ describe('LegacyJavaScript audit', () => {
'Object.defineProperty(String.prototype, "repeat", function() {})',
'$export($export.S,"Object",{values:function values(t){return i(t)}})',
'String.raw = function() {}',
// es-shims (object.entries)
'no(Object,{entries:r},{entries:function',
'no(Array.prototype,{find:r},{find:function',
// Currently are no polyfills that declare a class. Maybe in the future.
// 'Object.defineProperty(window, \'WeakMap\', function() {})',
// 'WeakMap = function() {}',
Expand Down Expand Up @@ -255,7 +258,11 @@ describe('LegacyJavaScript audit', () => {

it('detects non-corejs modules from source maps', async () => {
const map = {
sources: ['node_modules/focus-visible/dist/focus-visible.js'],
sources: [
'node_modules/focus-visible/dist/focus-visible.js',
'node_modules/array.prototype.find/index.js',
'node_modules/object.entries/index.js',
],
mappings: 'blah',
};
const script = {
Expand All @@ -266,13 +273,22 @@ describe('LegacyJavaScript audit', () => {
const result = await getResult([script]);

expect(result.items).toHaveLength(1);
expect(result.items[0].subItems.items).toHaveLength(3);
expect(result.items[0].subItems.items).toMatchObject([
{
signal: 'focus-visible',
location: {line: 0, column: 0},
},
{
signal: 'Array.prototype.find',
location: {line: 0, column: 0},
},
{
signal: 'Object.entries',
location: {line: 0, column: 0},
},
]);
expect(result.items[0].wastedBytes).toBe(3000);
expect(result.items[0].wastedBytes).toBe(38062);
});
});

Expand Down
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