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Cheapen process.env.NODE_ENV lookups in CommonJS bundles. #7627

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Jan 29, 2021
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Cheapen process.env.NODE_ENV lookups in CommonJS bundles. #7627

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Cheapen process.env.NODE_ENV lookups in CommonJS bundles.
benjamn Jan 28, 2021
e5c8654
Mention PR #7627 in CHANGELOG.md.
benjamn Jan 29, 2021
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21 changes: 21 additions & 0 deletions config/rollup.config.js
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,27 @@ function prepareBundle({
sourcemap: true,
exports: 'named',
externalLiveBindings: false,
// In Node.js, where these CommonJS bundles are most commonly used,
// the expression process.env.NODE_ENV can be very expensive to
// evaluate, because process.env is a wrapper for the actual OS
// environment, and lookups are not cached. We need to preserve the
// syntax of process.env.NODE_ENV expressions for dead code
// elimination to work properly, but we can apply our own caching by
// shadowing the global process variable with a stripped-down object
// that saves a snapshot of process.env.NODE_ENV when the bundle is
// first evaluated. If we ever need other process properties, we can
// add more stubs here.
intro: '!(function (process) {',
outro: [
'}).call(this, {',
' env: {',
' NODE_ENV: typeof process === "object"',
' && process.env',
' && process.env.NODE_ENV',
' || "development"',
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@benjamn benjamn Jan 29, 2021 •
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This conditional logic should allow this code to run safely in environments that do not define a global process variable, or that define process but not process.env or process.env.NODE_ENV.

' }',
'});',
].join('\n'),
},
plugins: [
extensions ? nodeResolve({ extensions }) : nodeResolve(),
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