This PR documents the new ExistFilter behavior proposed in the pull request api-platform/core#2243.

Author: jpdz8005

core/configuration.md

@@ -89,10 +89,13 @@ api_platform:
         api_keys: []
 
     collection:
+        # The name of the query parameter to filter nullable results (with the ExistsFilter).
+        notnull_parameter_name: 'exists'
+
         # The default order of results.
         order: 'ASC'
 
-        # The name of the query parameter to order results.
+        # The name of the query parameter to order results (with the OrderFilter).
         order_parameter_name: 'order'
 
         pagination:

core/filters.md

@@ -361,7 +361,7 @@ You can filter offers by joining two values, for example: `/offers?price[gt]=12.
 
 The exists filter allows you to select items based on nullable field value.
 
-Syntax: `?property[exists]=<true|false|1|0>`
+Syntax: `?exists[property]=<true|false|1|0>`
 
 Enable the filter:
 
@@ -385,10 +385,22 @@ class Offer
 }
 ```
 
-Given that the collection endpoint is `/offers`, you can filter offers on nullable field with the following query: `/offers?transportFees[exists]=true`.
+Given that the collection endpoint is `/offers`, you can filter offers on nullable field with the following query: `/offers?exists[transportFees]=true`.
 
 It will return all offers where `transportFees` is not `null`.
 
+#### Using a Custom NotNull Query Parameter Name
+
+A conflict will occur if `exists` is also the name of a property with the search filter enabled.
+Luckily, the query parameter name to use is configurable:
+
+```yaml
+# api/config/packages/api_platform.yaml
+api_platform:
+    collection:
+        notnull_parameter_name: 'notempty' # the URL query parameter to use is now "notempty"
+```
+
 ### Order Filter (Sorting)
 
 The order filter allows to sort a collection against the given properties.
@@ -680,7 +692,7 @@ final class RegexpFilter extends AbstractContextAwareFilter
         ) {
             return;
         }
-        
+
         $parameterName = $queryNameGenerator->generateParameterName($property); // Generate a unique parameter name to avoid collisions with other filters
         $queryBuilder
             ->andWhere(sprintf('REGEXP(o.%s, :%s) = 1', $property, $parameterName))
@@ -1074,7 +1086,7 @@ class DummyCar
      * @ApiFilter(SearchFilter::class, properties={"colors.prop": "ipartial"})
      */
     private $colors;
-    
+
     // ...
 }