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Inline destructured requires (#2087)
`inlineRequires` only inlined requires assigned to an identifier, so `const {foo} = require('foo')` stayed eager at module scope unless a Babel preset had lowered the destructuring first. `@react-native/babel-preset` stopped lowering destructuring for Hermes profiles in react/react-native#58965. This inlines top-level object patterns with plain, renamed or string keys directly: each reference becomes `require('foo').foo`, matching the lowered form. With `memoizeCalls`, a module's properties share one memoized module. Defaults, rest elements, nesting and computed keys are left alone, as are reassigned bindings and properties assigned on the module. Changelog: [Performance] Inline destructured CommonJS requires (`const {foo} = require('foo')`) under `inlineRequires`
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Lines changed: 431 additions & 3 deletions

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‎packages/metro-transform-plugins/src/__tests__/__snapshots__/inline-requires-plugin-test.js.snap‎

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@@ -7,6 +7,16 @@ var foo = require(\\"foo\\");
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↓ ↓ ↓ ↓ ↓ ↓
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"
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`;
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exports[`memoizeCalls=false: inline-requires deletes unused destructured requires: deletes unused destructured requires 1`] = `
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"
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const {a} = require(\\"foo\\");
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↓ ↓ ↓ ↓ ↓ ↓
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`;
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`;
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exports[`memoizeCalls=false: inline-requires ignores destructured properties that are re-assigned: ignores destructured properties that are re-assigned 1`] = `
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"
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var X = require(\\"X\\");
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const {a} = require(\\"X\\");
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X.a = function() {
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a();
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};
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↓ ↓ ↓ ↓ ↓ ↓
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const {
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a
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} = require(\\"X\\");
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require(\\"X\\").a = function () {
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a();
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};
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"
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`;
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exports[`memoizeCalls=false: inline-requires ignores require properties (as identifiers) that are re-assigned: ignores require properties (as identifiers) that are re-assigned 1`] = `
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"
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var X = require(\\"X\\");
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"
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`;
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exports[`memoizeCalls=false: inline-requires inlines destructured requires referenced across scopes: inlines destructured requires referenced across scopes 1`] = `
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"
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const {a, b} = require(\\"foo\\");
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function f() {
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return a() + b();
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}
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function g() {
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if (b()) {
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a();
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}
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}
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↓ ↓ ↓ ↓ ↓ ↓
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function f() {
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return require(\\"foo\\").a() + require(\\"foo\\").b();
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}
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function g() {
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if (require(\\"foo\\").b()) {
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require(\\"foo\\").a();
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}
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}
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"
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`;
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exports[`memoizeCalls=false: inline-requires inlines destructured requires: inlines destructured requires 1`] = `
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"
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const {a, b: c, \\"d-e\\": de} = require(\\"foo\\");
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a();
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c.x();
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de();
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↓ ↓ ↓ ↓ ↓ ↓
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require(\\"foo\\").a();
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require(\\"foo\\").b.x();
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require(\\"foo\\")[\\"d-e\\"]();
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"
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`;
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exports[`memoizeCalls=false: inline-requires inlines functions provided via \`inlineableCalls\`: inlines functions provided via \`inlineableCalls\` 1`] = `
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const inlinedCustom = customStuff(\\"foo\\");
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"
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`;
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exports[`memoizeCalls=true: inline-requires deletes unused destructured requires: deletes unused destructured requires 1`] = `
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"
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const {a} = require(\\"foo\\");
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`;
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`;
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exports[`memoizeCalls=true: inline-requires ignores destructured properties that are re-assigned: ignores destructured properties that are re-assigned 1`] = `
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"
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var X = require(\\"X\\");
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const {a} = require(\\"X\\");
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X.a = function() {
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a();
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};
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↓ ↓ ↓ ↓ ↓ ↓
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var X;
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const {
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a
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} = require(\\"X\\");
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(X || (X = require(\\"X\\"))).a = function () {
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a();
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};
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"
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`;
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exports[`memoizeCalls=true: inline-requires ignores require properties (as identifiers) that are re-assigned: ignores require properties (as identifiers) that are re-assigned 1`] = `
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var X = require(\\"X\\");
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`;
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exports[`memoizeCalls=true: inline-requires inlines destructured requires referenced across scopes: inlines destructured requires referenced across scopes 1`] = `
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"
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const {a, b} = require(\\"foo\\");
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function f() {
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return a() + b();
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}
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function g() {
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if (b()) {
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a();
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}
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}
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var _foo;
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function f() {
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return (_foo || (_foo = require(\\"foo\\"))).a() + _foo.b();
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}
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function g() {
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if ((_foo || (_foo = require(\\"foo\\"))).b()) {
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(_foo || (_foo = require(\\"foo\\"))).a();
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}
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}
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`;
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exports[`memoizeCalls=true: inline-requires inlines destructured requires: inlines destructured requires 1`] = `
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const {a, b: c, \\"d-e\\": de} = require(\\"foo\\");
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a();
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c.x();
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de();
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var _foo;
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(_foo || (_foo = require(\\"foo\\"))).a();
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_foo.b.x();
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_foo[\\"d-e\\"]();
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"
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`;
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exports[`memoizeCalls=true: inline-requires inlines functions provided via \`inlineableCalls\`: inlines functions provided via \`inlineableCalls\` 1`] = `
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const inlinedCustom = customStuff(\\"foo\\");

‎packages/metro-transform-plugins/src/__tests__/inline-requires-plugin-test.js‎

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@@ -238,6 +238,97 @@ const TEST_CASES: TestCases = {
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code: ['const a = require("Foo", "Bar", 47);', '', 'a();'].join('\n'),
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snapshot: true,
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},
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'inlines destructured requires': {
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code: [
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'const {a, b: c, "d-e": de} = require("foo");',
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'a();',
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'c.x();',
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'de();',
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].join('\n'),
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snapshot: true,
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},
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'inlines destructured requires referenced across scopes': {
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code: [
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'const {a, b} = require("foo");',
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'function f() {',
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' return a() + b();',
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'}',
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'function g() {',
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' if (b()) {',
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' a();',
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' }',
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'}',
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].join('\n'),
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snapshot: true,
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},
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'deletes unused destructured requires': {
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code: ['const {a} = require("foo");'].join('\n'),
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snapshot: true,
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},
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'ignores destructured requires with defaults': {
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code: ['const {', ' a = 1', '} = require("foo");', 'a();'].join('\n'),
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snapshot: false,
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},
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'ignores destructured requires with rest elements': {
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code: [
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'const {',
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' a,',
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' ...rest',
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'} = require("foo");',
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'a(rest);',
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].join('\n'),
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snapshot: false,
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},
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'ignores nested destructured requires': {
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code: [
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'const {',
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' a: {',
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' b',
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' }',
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'} = require("foo");',
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'b();',
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].join('\n'),
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snapshot: false,
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},
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'ignores destructured requires with computed keys': {
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code: ['const {', ' [key]: a', '} = require("foo");', 'a();'].join('\n'),
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snapshot: false,
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},
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'ignores destructured requires that are re-assigned': {
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code: [
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'let {',
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' a,',
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' b',
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'} = require("foo");',
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'b = 1;',
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'a(b);',
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].join('\n'),
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snapshot: false,
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},
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'ignores destructured properties that are re-assigned': {
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code: [
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'var X = require("X");',
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'const {a} = require("X");',
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'X.a = function() {',
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' a();',
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'};',
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].join('\n'),
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snapshot: true,
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},
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'ignores destructured requires in `ignoredRequires`': {
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code: ['const {', ' a', '} = require("CommonFoo");', 'a();'].join('\n'),
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snapshot: false,
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},
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};
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describe.each([true, false])('memoizeCalls=%s:', memoizeCalls => {

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