Adds changelog and flag information for process.env population (#20642)

Adds changelog and flag information for process.env population

Author: mikenomitch

src/content/changelog/workers/2025-03-11-process-env-support.mdx

@@ -0,0 +1,32 @@
+---
+title: Access your Worker's environment variables from process.env
+description: With Node.js compatability on, process.env is automatically populated with environment variables and secrets
+products:
+  - workers
+date: 2025-03-11T15:00:00Z
+---
+
+You can now access [environment variables](/workers/configuration/environment-variables/) and
+[secrets](/workers/configuration/secrets/) on [`process.env`](/workers/runtime-apis/nodejs/process/#processenv)
+when using the [`nodejs_compat` compatability flag](/workers/configuration/compatibility-flags/#nodejs-compatibility-flag).
+
+```js
+const apiClient = ApiClient.new({ apiKey: process.env.API_KEY });
+const LOG_LEVEL = process.env.LOG_LEVEL || "info";
+```
+
+In Node.js, environment variables are exposed via the global `process.env` object. Some libraries
+assume that this object will be populated, and many developers may be used to accessing variables
+in this way.
+
+Previously, the `process.env` object was always empty unless written to in Worker code. This could
+cause unexpected errors or friction when developing Workers using code previously written for Node.js.
+
+Now, [environment variables](/workers/configuration/environment-variables/),
+[secrets](/workers/configuration/secrets/), and [version metadata](/workers/runtime-apis/bindings/version-metadata/)
+can all be accessed on `process.env`.
+
+After April 1, 2025, populating `process.env` will become the default behavior when `nodejs_compat` is enabled, and
+your Worker's compatability date is after "2025-04-01". Until then, users can opt-in to this behavior by adding the
+[`nodejs_compat_populate_process_env`](/workers/configuration/compatibility-flags/#enable-auto-populating-processenv)
+compatability flag.

src/content/compatibility-flags/nodejs-compat-populate-process-env.md

@@ -0,0 +1,25 @@
+---
+name: "Enable auto-populating `process.env`"
+sort_date: "2025-02-27"
+enable_date: "2025-04-01"
+enable_flag: "nodejs_compat_populate_process_env"
+disable_flag: "nodejs_compat_do_not_populate_process_env"
+---
+
+When you enable the `nodejs_compat_populate_process_env` compatibility flag and the [`nodejs_compat`](/workers/runtime-apis/nodejs/)
+flag is also enabled, `process.env` will be populated with values from any bindings with text or JSON values.
+This means that if you have added [environment variables](/workers/configuration/environment-variables/),
+[secrets](/workers/configuration/secrets/), or [version metadata](/workers/runtime-apis/bindings/version-metadata/)
+bindings, these values can be accessed on `process.env`.
+
+```js
+const apiClient = ApiClient.new({ apiKey: process.env.API_KEY });
+const LOG_LEVEL = process.env.LOG_LEVEL || "info";
+```
+
+This makes accessing these values easier and conforms to common Node.js patterns, which can
+reduce toil and help with compatability for existing Node.js libraries.
+
+If users do not wish for these values to be accessible via `process.env`, they can use the
+`nodejs_compat_do_not_populate_process_env` flag. In this case, `process.env` will still be
+available, but will not have values automatically added.

src/content/docs/workers/runtime-apis/nodejs/process.mdx

@@ -26,7 +26,10 @@ nextTick(() => {
 
 ## `process.env`
 
-In the Node.js implementation of `process.env`, the `env` object is a copy of the environment variables at the time the process was started. In the Workers implementation, there is no process-level environment, so `env` is an empty object. You can still set and get values from `env`, and those will be globally persistent for all Workers running in the same isolate and context (for example, the same Workers entry point).
+In the Node.js implementation of `process.env`, the `env` object is a copy of the environment variables at the time the process was started. In the Workers implementation, there is no process-level environment, so by default `env` is an empty object. You can still set and get values from `env`, and those will be globally persistent for all Workers running in the same isolate and context (for example, the same Workers entry point).
+
+When [Node.js compatability](/workers/runtime-apis/nodejs/) is turned on and the [`nodejs_compat_populate_process_env`](/workers/configuration/compatibility-flags/#enable-auto-populating-processenv) compatability flag is set, `process.env` will contain any [environment variables](/workers/configuration/environment-variables/),
+[secrets](/workers/configuration/secrets/), or [version metadata](/workers/runtime-apis/bindings/version-metadata/) metadata that has been configured on your Worker.
 
 ### Relationship to per-request `env` argument in `fetch()` handlers