handling of `process.env.NODE_ENV` default in wrangler

[vicb]

Prerequisite: #10983

As of today process.env.NODE_ENV is left undefined by wrangler unless it is an explicitly set environment variable at build time or there is a define in the wrangler config:

workers-sdk/packages/wrangler/src/deployment-bundle/bundle.ts

Lines 386 to 396 in 7d0417b

	...(process.env.NODE_ENV && {
	define: {
	...(defineNavigatorUserAgent
	? { "navigator.userAgent": `"Cloudflare-Workers"` }
	: {}),
	// use process.env["NODE_ENV" + ""] so that esbuild doesn't replace it
	// when we do a build of wrangler. (re: https://github.com/cloudflare/workers-sdk/issues/1477)
	"process.env.NODE_ENV": `"${process.env["NODE_ENV" + ""]}"`,
	...define,
	},
	}),

However many packages are optimized for prod when process.env.NODE_ENV === "production".

We should align with what Vite does:

• default to "production" for wrangler deploy/upload
• default to "development" for wrangler dev

Note that the default should still be overridable using a build time process.env.NODE_ENV (which include .env* files) and wrangler define config.

There are a couples of existing issues that would be solved:

• 🐛 BUG: env.process.NODE_ENV returns 'undefined' in Cloudflare Workers #9802
• 🐛 BUG: process.env.NODE_ENV is not set to production by default #7886

ref: internal discussion1, discussion 2