Add rule for detecting expensive calls on a Collection

README.md

@@ -71,6 +71,8 @@ If you are getting the error `Allowed memory size exhausted`, then you can use t
 ./vendor/bin/phpstan analyse --memory-limit=2G
 ```
 
+## Rules
+A list of configurable rules specific to Laravel can be found [here](docs/rules.md).
 ## 👊🏻 Contributing
 
 Thank you for considering contributing to Larastan. All the contribution guidelines are mentioned [here](CONTRIBUTING.md).

docs/rules.md

@@ -0,0 +1,53 @@
+# Rules
+
+All rules that are specific to Laravel applications 
+are listed here with their configurable options.
+
+
+## NoUnnecessaryCollectionCall
+
+Checks for method calls on instances of `Illuminate\Support\Collection` and their 
+subclasses. If the same result could have been determined 
+directly with a query then this rule will produce an error.
+This rule exists to reduce unnecessarily heavy queries on the database 
+and to prevent unneeded loops over Collections.
+
+#### Examples
+```php
+User::all()->count();
+$user->roles()->pluck('name')->contains('a role name');
+```
+
+Will result in the following errors:
+```
+[NoUnnecessaryCollectionCallRule] Called 'count' on collection, but could have been retrieved as a query.
+[NoUnnecessaryCollectionCallRule] Called 'contains' on collection, but could have been retrieved as a query.
+```
+
+To fix the errors, the code in the previous example could be changed to:
+```php
+User::count();
+$user->roles()->where('name', 'a role name')->exists();
+```
+
+#### Configuration
+This rule is enabled by default. To disable it completely, add:
+```
+noUnnecessaryCollectionCall: false
+```
+to your `phpstan.neon` file.
+
+You can also configure the collection methods which this rule 
+checks for. By default, all collection methods are checked. 
+To only enable a specific set of methods, you could set the
+ `noUnnecessaryCollectionCallOnly` configuration key. For example:
+```
+noUnnecessaryCollectionCallOnly: ['count', 'first']
+```
+will only throw errors on the `count` and `first` methods.
+The inverse is also configurable, to not throw an exception
+on the `contains` method, one could set the following value:
+```
+noUnnecessaryCollectionCallExcept: ['contains']
+```
+

extension.neon

@@ -33,6 +33,18 @@ parameters:
     bootstrap: %rootDir%/../../nunomaduro/larastan/bootstrap.php
     reportUnmatchedIgnoredErrors: false
     checkGenericClassInNonGenericObjectType: false
+    noUnnecessaryCollectionCall: true
+    noUnnecessaryCollectionCallOnly: []
+    noUnnecessaryCollectionCallExcept: []
+
+parametersSchema:
+    noUnnecessaryCollectionCall: bool()
+    noUnnecessaryCollectionCallOnly: listOf(string())
+    noUnnecessaryCollectionCallExcept: listOf(string())
+
+conditionalTags:
+    NunoMaduro\Larastan\Rules\NoUnnecessaryCollectionCallRule:
+    		phpstan.rules.rule: %noUnnecessaryCollectionCall%
 
 services:
     -
@@ -194,6 +206,12 @@ services:
         tags:
             - phpstan.phpDoc.typeNodeResolverExtension
 
+    -
+        class: NunoMaduro\Larastan\Rules\NoUnnecessaryCollectionCallRule
+        arguments:
+            onlyMethods: %noUnnecessaryCollectionCallOnly%
+            excludeMethods: %noUnnecessaryCollectionCallExcept%
+
     -
         class: NunoMaduro\Larastan\Types\GenericEloquentBuilderTypeNodeResolverExtension
         tags: