refactor(kernel-utils): replace vat bundler NODE_ENV define with a plugin

[rekmarks]

Summary

Moves process.env.NODE_ENV injection out of the bundleVat build config and into a dedicated, auto-detecting Rolldown transform plugin, resolving #812.

Previously bundleVat configured a Vite define that textually substituted process.env.NODE_ENV → "production" on every build. It was a workaround for libraries (e.g. immer) that branch on process.env.NODE_ENV, but baking it into the build config coupled bundling to an env-shimming concern. The new replaceNodeEnvPlugin makes that logic a first-class, unit-tested plugin instead.

Changes

• New replaceNodeEnvPlugin (packages/kernel-utils/src/vite-plugins/replace-node-env-plugin.ts) — a Rolldown transform plugin that inlines process.env.NODE_ENV as a string literal in any module referencing it, and no-ops otherwise. Mirrors the sibling removeDynamicImportsPlugin.
• Configurable value — the plugin accepts an options bag { value } (type ReplaceNodeEnvPluginOptions), defaulting to 'production', so callers can inline a different process.env.NODE_ENV value.
• bundle-vat.ts — removed the define block (and its TODO) and added replaceNodeEnvPlugin() to the rolldownOptions.plugins array (uses the 'production' default).
• index.ts — exports the new plugin and its options type alongside removeDynamicImportsPlugin.
• Tests — replace-node-env-plugin.test.ts covers positive/negative cases, the quoted-literal assertion, the word-boundary near-miss (NODE_ENVIRONMENT), and a configured non-default value.

Behavior

For the default value, output is identical to the old define for any bundle referencing process.env.NODE_ENV — the logic is just relocated to a named, tested plugin.

Verification

• yarn workspace @metamask/kernel-utils build — passes.
• yarn workspace @metamask/kernel-utils test:dev:quiet — passes (new + existing plugin/index tests).
• End-to-end: bundling a fixture that reads process.env.NODE_ENV produced var isProd = true; var rawMode = "production"; — fully inlined and constant-folded, no residual process.env.NODE_ENV reference.
• yarn lint — clean.

Closes #812

🤖 Generated with Claude Code

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Note

Low Risk
Build-time bundling refactor with equivalent default behavior; limited to kernel-utils vat bundling and covered by new tests.

Overview
bundleVat no longer sets a global Vite define for process.env.NODE_ENV. That injection is handled by a new Rolldown replaceNodeEnvPlugin, wired into the vat bundle pipeline alongside the existing dynamic-import stripper.

The plugin only transforms modules that reference process.env.NODE_ENV, replacing them with a JSON-stringified literal (default "production", overridable via { value }). That keeps vat bundles safe for deps like immer when there is no runtime process global, without coupling every build to a blanket define.

replaceNodeEnvPlugin and ReplaceNodeEnvPluginOptions are exported from ./vite-plugins, with unit tests covering replacements, no-ops, word boundaries, and custom values. CHANGELOG documents the addition.

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[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	71.38% ⬆️ +0.02%	8869 / 12424
🔵	Statements	71.21% ⬆️ +0.02%	9019 / 12665
🔵	Functions	72.59% ⬆️ +0.02%	2140 / 2948
🔵	Branches	64.9% ⬆️ +0.04%	3584 / 5522

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
packages/kernel-utils/src/vite-plugins/bundle-vat.ts	41.66% 🟰 ±0%	50% 🟰 ±0%	40% 🟰 ±0%	41.66% 🟰 ±0%	76-131
packages/kernel-utils/src/vite-plugins/index.ts	100% 🟰 ±0%	100% 🟰 ±0%	100% 🟰 ±0%	100% 🟰 ±0%
packages/kernel-utils/src/vite-plugins/replace-node-env-plugin.ts	100%	100%	100%	100%

Generated in workflow #4501 for commit 8f73140 by the Vitest Coverage Report Action