Discuss params when webpack.config.js exports a function

* Expand on how --env arguments gets translated into the env parameter.

* Briefly explain the argv parameter.

Author: jennings

content/api/cli.md

@@ -110,16 +110,6 @@ Specifies a different [configuration](/configuration) file to pick up. Use this
 webpack --config example.config.js
 ```
 
-**Specify build environment**
-
-Send [environment](/configuration/configuration-types) variable to be used in webpack config file.
-
-
-```bash
-webpack --env.production    # sets production to true
-webpack --env.platform=web  # sets platform to "web"
-```
-
 **Print result of webpack as a JSON**
 
 ```bash
@@ -129,6 +119,25 @@ webpack --json > stats.json
 
 In every other case, webpack prints out a set of stats showing bundle, chunk and timing details. Using this option the output can be a JSON object. This response is accepted by webpack's [analyse tool](https://webpack.github.com/analyse), or chrisbateman's [webpack-visualizer](https://chrisbateman.github.io/webpack-visualizer/), or th0r's [webpack-bundle-analyzer](https://github.com/th0r/webpack-bundle-analyzer). The analyse tool will take in the JSON and provide all the details of the build in graphical form.
 
+### Environment Options
+
+When the webpack configuration [exports a function](/configuration/configuration-types#exporting-a-function), an "environment" may be passed to it.
+
+```bash
+webpack --env.production    # sets env.production == true
+webpack --env.platform=web  # sets env.platform == "web"
+```
+
+The `--env` argument accepts various syntaxes:
+
+| Invocation                    | Resulting environment       |
+|-------------------------------|-----------------------------|
+| webpack --env prod            | `"prod"`                    |
+| webpack --env.prod            | `{ prod: true }`            |
+| webpack --env.prod=1          | `{ prod: 1 }`               |
+| webpack --env.prod=foo        | `{ prod: "foo" }`           |
+| webpack --env.prod --env.min  | `{ prod: true, min: true }` |
+| webpack --env.prod --env min  | `[{ prod: true }, "min"]`   |
 
 ### Output Options
 

content/configuration/configuration-types.md

@@ -11,21 +11,25 @@ contributors:
 Besides exporting a single config object, there are a few more ways that cover other needs as well.
 
 
-## Exporting a function to use `--env`
+## Exporting a Function
 
 Eventually you will find the need to disambiguate in your `webpack.config.js` between [development](/guides/development) and [production builds](/guides/production). You have (at least) two options:
 
-Instead of exporting a configuration object, you may return a function which accepts an environment as argument. When running webpack, you may specify build environment keys via `--env`, such as `--env.production` or `--env.platform=web`.
+One option is to export a function from your webpack config instead of exporting an object. The function will be invoked with two arguments:
+
+* An environment as the first parameter. See the [environment options CLI documentation](/api/cli#environment-options) for syntax examples.
+* An options map (`argv`) as the second parameter. This describes the options passed to webpack, with keys such as [`output-filename`](/api/cli/#output-options) and [`optimize-minimize`](/api/cli/#optimize-options).
 
 ```diff
 -module.exports = {
-+module.exports = function(env) {
++module.exports = function(env, argv) {
 +  return {
-    plugins: [
-      new webpack.optimize.UglifyJsPlugin({
-+        compress: env.production // compress only in production build
-      })
-    ]
++    devtool: env.production ? 'source-maps' : 'eval',
+     plugins: [
+       new webpack.optimize.UglifyJsPlugin({
++        compress: argv['optimize-minimize'] // only if -p or --optimize-minimize were passed
+       })
+     ]
 +  };
 };
 ```