Incorrect define replacement in build

[bluwy]

Describe the bug

When building a project that uses import.meta.env.UNKNOWN, it is being replaced as MODE:"production",DEV:!1,PROD:!0}.UNKNOWN instead of ({}).UNKNOWN.

Ref #8090 (Additional context)

Bug introduced in #5972 in Vite 3. Line 50 is never being used, and skips to line 51 instead.

vite/packages/vite/src/node/plugins/define.ts

Lines 42 to 53 in 908c9e4

	const env: Record<string, any> = {
	...config.env,
	SSR: !!config.build.ssr
	}
	for (const key in env) {
	importMetaKeys[`import.meta.env.${key}`] = JSON.stringify(env[key])
	}
	Object.assign(importMetaKeys, {
	'import.meta.env.': `({}).`,
	'import.meta.env': JSON.stringify(config.env),
	'import.meta.hot': `false`
	})

This not only happens for import.meta.env., but process.env. to for ssr builds. And other similar usage.

Reproduction

Vite 3: https://stackblitz.com/edit/vitejs-vite-b1md2x?file=main.js&terminal=build,preview
Vite 2.9: https://stackblitz.com/edit/vitejs-vite-ouwh65?file=main.js&terminal=build,preview

System Info

Vite 3

Used Package Manager

pnpm

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[julienv3]

@tony19 it does not seem like #9791 fixes the issue.
The problem lies in the negative lookahead in the regex used for replacements, it will never match "import.meta.env." (or any other .-ending replacement) because it rejects the match when it's followed by a letter or a number.
Sent a PR addressing this issue specifically in #10958 with tests.