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Clarify conditions under which process.env expressions are inlined #33212

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merged 3 commits into from
May 22, 2022
Merged

Clarify conditions under which process.env expressions are inlined #33212

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Clarify conditions under which process.env expressions are inlined
jameshfisher Jan 12, 2022
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Apply suggestions from code review
ijjk May 22, 2022
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Merge branch 'canary' into patch-2
ijjk May 22, 2022
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15 changes: 14 additions & 1 deletion docs/basic-features/environment-variables.md
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Expand Up @@ -93,7 +93,8 @@ This loads `process.env.NEXT_PUBLIC_ANALYTICS_ID` into the Node.js environment a
// pages/index.js
import setupAnalyticsService from '../lib/my-analytics-service'

// NEXT_PUBLIC_ANALYTICS_ID can be used here as it's prefixed by NEXT_PUBLIC_
// 'NEXT_PUBLIC_ANALYTICS_ID' can be used here as it's prefixed by 'NEXT_PUBLIC_'.
// It will be transformed at build time to `setupAnalyticsService('abcdefghijk')`.
setupAnalyticsService(process.env.NEXT_PUBLIC_ANALYTICS_ID)

function HomePage() {
Expand All @@ -103,6 +104,18 @@ function HomePage() {
export default HomePage
```

Note that dynamic lookups will _not_ be inlined, such as:

```js
// This will NOT be inlined, because it uses a variable
const varName = 'NEXT_PUBLIC_ANALYTICS_ID'
setupAnalyticsService(process.env[varName])

// This will NOT be inlined, because it uses a variable
const env = process.env
setupAnalyticsService(env.NEXT_PUBLIC_ANALYTICS_ID)
```

## Default Environment Variables

In general only one `.env.local` file is needed. However, sometimes you might want to add some defaults for the `development` (`next dev`) or `production` (`next start`) environment.
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