✨ Allow the user to modify the query and exported fields.

README.md

@@ -96,6 +96,32 @@ class User extends Resource
 
 More installation instructions can be found at: [https://docs.laravel-excel.com/nova/1.1/getting-started/installation.html](https://docs.laravel-excel.com/nova/1.1/getting-started/installation.html)
 
+## Modify your export
+
+Currently the export is based on the index fields but this might not be what you want to do.  
+You can modify with ease the query and the exported fields this way:
+
+```php
+    /**
+     * Get the actions available for the resource.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @return array
+     */
+    public function actions(Request $request)
+    {
+        return [
+            (new DownloadExcel)
+                ->alterateQuery(function ($query) {
+                    $query->select('id', 'first_name');
+                })
+                ->exportFields(['first_name', 'id']),
+        ];
+    }
+```
+
+Feel free to join tables if necessary but you should always select the fields you want to export to avoid confusions.
+
 ## 🎓 Learning Laravel Excel
 
 You can find the full documentation of Laravel Nova Excel [on the website](https://docs.laravel-excel.com/nova).

src/Actions/ExportToExcel.php

@@ -51,6 +51,16 @@ class ExportToExcel extends Action implements FromQuery, WithCustomChunkSize, Wi
      */
     protected $resource;
 
+    /**
+     * @var callable|null
+     */
+    protected $callbackQuery;
+
+    /**
+     * @var array|null
+     */
+    protected $exportAttributes;
+
     /**
      * @var Builder
      */
@@ -90,6 +100,10 @@ public function handleRequest(ActionRequest $request)
         $this->handleOnly($this->request);
         $this->handleHeadings($query, $this->request);
 
+        if (is_callable($this->callbackQuery)) {
+            ($this->callbackQuery)($query);
+        }
+
         return $this->handle($request, $this->withQuery($query));
     }
 
@@ -119,6 +133,31 @@ public function handle(ActionRequest $request, Action $exportable): array
             : Action::message(__('Resource was successfully exported.'));
     }
 
+    /**
+     * @param callable $callable
+     *
+     * @return $this
+     */
+    public function tapQuery(callable $callable)
+    {
+        $this->callbackQuery = $callable;
+
+        return $this;
+    }
+
+    /**
+     * Sets the attributes to be selected.
+     *
+     * @param array|mixed $exportAttributes
+     * @return $this
+     */
+    public function exportAttributes($exportAttributes)
+    {
+        $this->exportAttributes = is_array($exportAttributes) ? $exportAttributes : func_get_args();
+
+        return $this;
+    }
+
     /**
      * @param callable $callback
      *
@@ -237,33 +276,42 @@ protected function getDefaultExtension(): string
     protected function replaceFieldValuesWhenOnResource(Model $model, array $only = []): array
     {
         $resource = $this->resolveResource($model);
-        $fields   = $this->resourceFields($resource);
+        $fields   = $this->exportAttributes ?? $this->resourceFields($resource);
 
         $row = [];
-        foreach ($fields as $field) {
-            if (!$this->isExportableField($field)) {
-                continue;
-            }
 
-            if (\in_array($field->attribute, $only, true)) {
-                $row[$field->attribute] = $field->value;
-            } elseif (\in_array($field->name, $only, true)) {
-                // When no field could be found by their attribute name, it's most likely a computed field.
-                $row[$field->name] = $field->value;
+        // If custom user fields
+        if (is_array($fields)) {
+            foreach ($fields as $field) {
+                $row[$field] = $model->{$field};
+            }
+        } else {
+            // If index fields
+            foreach ($fields as $field) {
+                if (!$this->isExportableField($field)) {
+                    continue;
+                }
+
+                if (\in_array($field->attribute, $only, true)) {
+                    $row[$field->attribute] = $field->value;
+                } elseif (\in_array($field->name, $only, true)) {
+                    // When no field could be found by their attribute name, it's most likely a computed field.
+                    $row[$field->name] = $field->value;
+                }
             }
-        }
 
-        // Add fields that were requested by ->only(), but are not registered as fields in the Nova resource.
-        foreach (array_diff($only, array_keys($row)) as $attribute) {
-            if ($model->{$attribute}) {
-                $row[$attribute] = $model->{$attribute};
-            } else {
-                $row[$attribute] = '';
+            // Add fields that were requested by ->only(), but are not registered as fields in the Nova resource.
+            foreach (array_diff($only, array_keys($row)) as $attribute) {
+                if ($model->{$attribute}) {
+                    $row[$attribute] = $model->{$attribute};
+                } else {
+                    $row[$attribute] = '';
+                }
             }
-        }
 
-        // Fix sorting
-        $row = array_merge(array_flip($only), $row);
+            // Fix sorting
+            $row = array_merge(array_flip($only), $row);
+        }
 
         return $row;
     }