Update Cookbook direnv instructions for new std helper

cookbook/direnv.md

@@ -4,35 +4,46 @@ title: Direnv
 
 # Direnv
 
-Many people use [direnv](https://direnv.net) to load an environment upon entering a directory as well as unloading it when exiting the directory.
-Configuring direnv to work with nushell requires nushell version 0.66 or later.
+Many people use [direnv](https://direnv.net) to load an environment when entering a directory and unload it when exiting the directory.
 
----
+## How direnv works
+
+From [direnv.net](https://direnv.net):
+
+> Before each prompt, direnv checks for the existence of a `.envrc` file (and optionally a `.env` file) in the current and parent directories. If the file exists (and is authorized), it is loaded into a bash sub-shell and all exported variables are then captured by direnv and then made available to the current shell.
+
+## Configuring direnv in Nushell
+
+In Nushell, it's possible to run direnv each time the prompt displays (using a [`pre_prompt` hook](/book/hooks.html)). However, it's more efficient to update only when the directory is changed using an `env_change` hook along with:
+
+- [`from json`](/commands/docs/from_json.md) to convert the direnv output to structured data
+- [`load-env`](/commands/docs/load-env.md)
+- An `env-conversion` helper for the `PATH` from the [Standard Library](/book/standard_library.md)
 
-### Configuring direnv
+::: note
 
-To make direnv work with nushell the way it does with other shells, we can use the "hooks" functionality:
+The direnv configuration below requires Nushell 0.104 or later.
+
+:::
 
 ```nu
-$env.config = {
-  hooks: {
-    pre_prompt: [{ ||
-      if (which direnv | is-empty) {
-        return
-      }
-
-      direnv export json | from json | default {} | load-env
-      if 'ENV_CONVERSIONS' in $env and 'PATH' in $env.ENV_CONVERSIONS {
-        $env.PATH = do $env.ENV_CONVERSIONS.PATH.from_string $env.PATH
-      }
-    }]
+use std/config *
+
+# Initialize the PWD hook as an empty list if it doesn't exist
+$env.config.hooks.env_change.PWD = $env.config.hooks.env_change.PWD? | default []
+
+$env.config.hooks.env_change.PWD ++= [{||
+  if (which direnv | is-empty) {
+    # If direnv isn't installed, do nothing
+    return
   }
-}
+
+  direnv export json | from json | default {} | load-env
+  # If direnv changes the PATH, it will become a string and we need to re-convert it to a list
+  $env.PATH = do (env-conversions).path.from_string $env.PATH
+}]
 ```
 
-::: tip Note
-you can follow the [`nu_scripts` of Nushell](https://github.com/nushell/nu_scripts/blob/main/nu-hooks/nu-hooks/direnv/config.nu)
-for the always up-to-date version of the hook above
-:::
+As with other configuration changes, this can be made permanent by adding it to your startup [configuration](/book/configuration.md).
 
-With that configuration in place, direnv should now work with nushell.
+With this in place, direnv will now add/remove environment variables when entering/leaving a directory with an `.envrc` or `.env` file.