docs(*): clarify module API and dependency injection rules

Closes #16363

Author: Narretz

docs/content/guide/di.ngdoc

@@ -14,23 +14,30 @@ and providing them to other components as requested.
 
 ## Using Dependency Injection
 
-DI is pervasive throughout AngularJS. You can use it when defining components or when providing `run`
-and `config` blocks for a module.
-
-- Components such as services, directives, filters, and animations are defined by an injectable
-factory method or constructor function. These components can be injected with "service" and "value"
-components as dependencies.
-
-- Controllers are defined by a constructor function, which can be injected with any of the "service"
-and "value" components as dependencies, but they can also be provided with special dependencies. See
-{@link di#controllers Controllers} below for a list of these special dependencies.
-
-- The `run` method accepts a function, which can be injected with "service", "value" and "constant"
-components as dependencies. Note that you cannot inject "providers" into `run` blocks.
-
-- The `config` method accepts a function, which can be injected with "provider" and "constant"
-components as dependencies. Note that you cannot inject "service" or "value" components into
-configuration.
+Dependency Injection is pervasive throughout AngularJS. You can use it when defining components
+or when providing `run` and `config` blocks for a module.
+
+- {@link angular.Module#service Services}, {@link angular.Module#directive directives},
+{@link angular.Module#filter filters}, and {@link angular.Module#animation animations} are
+defined by an injectable factory method or constructor function, and can be injected with
+"service" and "value" as dependencies.
+
+- {@link ng.$controller Controllers} are defined by a constructor function, which can be injected
+with any of the "service" and "value" as dependencies, but they can also be provided with
+special dependencies. See {@link di#controllers Controllers} below for a list of these
+special dependencies.
+
+- The {@link angular.Module#run `run`} method accepts a function, which can be injected with
+"service", "value" and "constant" as dependencies. Note that you cannot inject "providers"
+into `run` blocks.
+
+- The {@link angular.Module#config `config`} method accepts a function, which can be injected with
+"provider" and "constant" as dependencies. Note that you cannot inject "service" or
+"value" components into configuration.
+
+- The {@link angular.Module#provider `provider`} method can only be injected with other "provider"
+injectables, and only with those that have been **registered beforehand**. This is different
+from services, where the order of registration does not matter.
 
 See {@link module#module-loading-dependencies Modules} for more details about `run` and `config`
 blocks.

docs/content/guide/module.ngdoc

@@ -3,12 +3,14 @@
 @sortOrder 320
 @description
 
-# What is a Module?
+# Modules
+
+## What is a Module?
 
 You can think of a module as a container for the different parts of your app – controllers,
 services, filters, directives, etc.
 
-# Why?
+## Why?
 
 Most applications have a main method that instantiates and wires together the different parts of
 the application.
@@ -23,7 +25,7 @@ should be bootstrapped. There are several advantages to this approach:
   * End-to-end tests can use modules to override configuration.
 
 
-# The Basics
+## The Basics
 
 I'm in a hurry. How do I get a Hello World module working?
 
@@ -65,7 +67,7 @@ Important things to notice:
     This array is the list of modules `myApp` depends on.
 
 
-# Recommended Setup
+## Recommended Setup
 
 While the example above is simple, it will not scale to large applications. Instead we recommend
 that you break your application to multiple modules like this:
@@ -136,39 +138,44 @@ The above is a suggestion. Tailor it to your needs.
 
 
 
-# Module Loading & Dependencies
+## Module Loading
 
-A module is a collection of configuration and run blocks which get applied to the application
-during the bootstrap process. In its simplest form the module consists of a collection of two kinds
-of blocks:
+A {@link angular.Module module} is a collection of providers, services, directives etc.,
+and optionally configuration and run blocks which get applied to the application during the
+bootstrap process.
 
-  1. **Configuration blocks** - get executed during the provider registrations and configuration
-    phase. Only providers and constants can be injected into configuration blocks. This is to
-    prevent accidental instantiation of services before they have been fully configured.
-  2. **Run blocks** - get executed after the injector is created and are used to kickstart the
-    application. Only instances and constants can be injected into run blocks. This is to prevent
-    further system configuration during application run time.
+The {@link angular.Module module API} describes all the available methods and how they can be used.
 
-```js
-angular.module('myModule', []).
-  config(function(injectables) { // provider-injector
-    // This is an example of config block.
-    // You can have as many of these as you want.
-    // You can only inject Providers (not instances)
-    // into config blocks.
-  }).
-  run(function(injectables) { // instance-injector
-    // This is an example of a run block.
-    // You can have as many of these as you want.
-    // You can only inject instances (not Providers)
-    // into run blocks
-  });
-```
+See {@link guide/di#using-dependency-injection Using Dependency Injection} to find out which
+dependencies can be injected in which injectables.
+
+### Dependencies and Order of execution
+
+Modules can list other modules as their dependencies. Depending on a module implies that the required
+module will be loaded before the requiring module is loaded.
+
+In a single module the order of execution is as follows:
+
+1. {@link angular.Module#provider provider} functions are executed, so they and the services they
+define can be made available to the {@link auto.$injector $injector}.
 
-## Configuration Blocks
+2. After that, the configuration blocks ({@link angular.Module#config config} functions) are executed.
+This means the configuration blocks of the required modules execute before the configuration blocks
+of any requiring module.
 
-There are some convenience methods on the module which are equivalent to the `config` block. For
-example:
+This continues until all module dependencies has been resolved.
+
+Then, the {@link angular.Module#run run} blocks that have been collected from each module are
+executed in order of requirement.
+
+Note that each module is only loaded once, even if multiple other modules require it.
+
+
+### Registering injectables in the config block
+
+While it is recommended to register injectables directly with the {@link angular.Module module API},
+it is also possible to register services, directives etc. by injecting into the config function
+{@link $provide $provide} or the individual service providers:
 
 ```js
 angular.module('myModule', []).
@@ -188,35 +195,22 @@ angular.module('myModule', []).
   });
 ```
 
-<div class="alert alert-info">
-When bootstrapping, first AngularJS applies all constant definitions.
-Then AngularJS applies configuration blocks in the same order they were registered.
-</div>
-
-## Run Blocks
+### Run Blocks
 
 Run blocks are the closest thing in AngularJS to the main method. A run block is the code which
 needs to run to kickstart the application. It is executed after all of the services have been
 configured and the injector has been created. Run blocks typically contain code which is hard
 to unit-test, and for this reason should be declared in isolated modules, so that they can be
 ignored in the unit-tests.
 
-## Dependencies
-
-Modules can list other modules as their dependencies. Depending on a module implies that the required
-module needs to be loaded before the requiring module is loaded. In other words the configuration
-blocks of the required modules execute before the configuration blocks of the requiring module.
-The same is true for the run blocks. Each module can only be loaded once, even if multiple other
-modules require it.
-
-## Asynchronous Loading
+### Asynchronous Loading
 
 Modules are a way of managing $injector configuration, and have nothing to do with loading of
 scripts into a VM. There are existing projects which deal with script loading, which may be used
 with AngularJS. Because modules do nothing at load time they can be loaded into the VM in any order
 and thus script loaders can take advantage of this property and parallelize the loading process.
 
-## Creation versus Retrieval
+### Creation versus Retrieval
 
 Beware that using `angular.module('myModule', [])` will create the module `myModule` and overwrite any
 existing module named `myModule`. Use `angular.module('myModule')` to retrieve an existing module.
@@ -235,7 +229,7 @@ var myModule = angular.module('myModule', []);
 var myModule = angular.module('myOtherModule');
 ```
 
-# Unit Testing
+## Unit Testing
 
 A unit test is a way of instantiating a subset of an application to apply stimulus to it.
 Small, structured modules help keep unit tests concise and focused.

src/auto/injector.js

@@ -440,6 +440,9 @@ function annotate(fn, strictDi, name) {
  * which lets you specify whether the {@link ng.$log $log} service will log debug messages to the
  * console or not.
  *
+ * It is possible to inject other providers into the provider function,
+ * but the injected provider must have been defined before the one that requires it.
+ *
  * @param {string} name The name of the instance. NOTE: the provider will be available under `name +
                         'Provider'` key.
  * @param {(Object|function())} provider If the provider is:

src/loader.js

@@ -344,7 +344,13 @@ function setupModuleLoader(window) {
            * @param {Function} configFn Execute this function on module load. Useful for service
            *    configuration.
            * @description
-           * Use this method to register work which needs to be performed on module loading.
+           * Use this method to configure services by injecting their
+           * {@link angular.Module#provider `providers`}, e.g. for adding routes to the
+           * {@link ngRoute.$routeProvider $routeProvider}.
+           *
+           * Note that you can only inject {@link angular.Module#provider `providers`} and
+           * {@link angular.Module#constant `constants`} into this function.
+           *
            * For more about how to configure services, see
            * {@link providers#provider-recipe Provider Recipe}.
            */