Fix groupBy to resolve dot-notation keys into SQL joins

Dot-notation column keys (e.g. contract.department.name) are Eloquent
relationship paths, not SQL columns. The groupBy/aggregate selectRaw
was using them directly, causing "column not found" errors.

- Add resolveColumnWithJoins() to walk the relationship chain and add
  proper joins for BelongsTo/HasOne/HasMany relationships
- Replace normal columns with group_value + aggregate columns when
  grouping is active
- Update displayColumns on groupBy/aggregate property changes

Closes #109

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: SimonBarrettACT

src/ReportBuilder.php

@@ -7,6 +7,10 @@
 use ACTTraining\QueryBuilder\Support\Concerns\WithReportBuilder;
 use Illuminate\Contracts\View\Factory;
 use Illuminate\Contracts\View\View;
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasOne;
 use Livewire\Attributes\Computed;
 
 abstract class ReportBuilder extends QueryBuilder
@@ -28,12 +32,66 @@ public function rowsQuery()
             return $query;
         }
 
-        $query->selectRaw("{$this->groupBy}, {$this->aggregateFunction}({$this->aggregateColumn}) as aggregate")
-            ->groupBy($this->groupBy);
+        $groupByColumn = $this->resolveColumnWithJoins($query, $this->groupBy);
+        $baseTable = $query->getModel()->getTable();
+        $aggregateColumn = str_contains($this->aggregateColumn, '.')
+            ? $this->resolveColumnWithJoins($query, $this->aggregateColumn)
+            : "{$baseTable}.{$this->aggregateColumn}";
+
+        $query->selectRaw("{$groupByColumn} as group_value, {$this->aggregateFunction}({$aggregateColumn}) as aggregate")
+            ->groupBy($groupByColumn);
 
         return $query;
     }
 
+    protected function resolveColumnWithJoins(Builder $query, string $key): string
+    {
+        if (! str_contains($key, '.')) {
+            return $query->getModel()->getTable().'.'.$key;
+        }
+
+        $parts = explode('.', $key);
+        $columnName = array_pop($parts);
+        $currentModel = $query->getModel();
+        $joined = [];
+
+        foreach ($parts as $relationName) {
+            if (! method_exists($currentModel, $relationName)) {
+                return $key;
+            }
+
+            $relation = $currentModel->{$relationName}();
+            $relatedTable = $relation->getRelated()->getTable();
+
+            if (in_array($relatedTable, $joined, true)) {
+                $currentModel = $relation->getRelated();
+
+                continue;
+            }
+
+            if ($relation instanceof BelongsTo) {
+                $query->join(
+                    $relatedTable,
+                    $currentModel->getTable().'.'.$relation->getForeignKeyName(),
+                    '=',
+                    $relatedTable.'.'.$relation->getOwnerKeyName()
+                );
+            } elseif ($relation instanceof HasOne || $relation instanceof HasMany) {
+                $query->join(
+                    $relatedTable,
+                    $currentModel->getTable().'.'.$currentModel->getKeyName(),
+                    '=',
+                    $relatedTable.'.'.$relation->getForeignKeyName()
+                );
+            }
+
+            $joined[] = $relatedTable;
+            $currentModel = $relation->getRelated();
+        }
+
+        return $currentModel->getTable().'.'.$columnName;
+    }
+
     public function render(): Factory|View
     {
         return view('query-builder::report-table');

src/Support/Concerns/WithReportBuilder.php

@@ -57,19 +57,19 @@ public function updatedSelectedColumns(): void
     public function updatedGroupBy(): void
     {
         $this->resetPage();
-        $this->dispatch('refreshTable')->self();
+        $this->displayColumns = $this->resolveColumns()->pluck('key')->toArray();
     }
 
     public function updatedAggregateFunction(): void
     {
         $this->resetPage();
-        $this->dispatch('refreshTable')->self();
+        $this->displayColumns = $this->resolveColumns()->pluck('key')->toArray();
     }
 
     public function updatedAggregateColumn(): void
     {
         $this->resetPage();
-        $this->dispatch('refreshTable')->self();
+        $this->displayColumns = $this->resolveColumns()->pluck('key')->toArray();
     }
 
     public function hasGroupBy(): bool
@@ -176,9 +176,14 @@ public function buildColumns(): array
         }
 
         if ($this->hasGroupBy()) {
-            $columns[] = Column::make('Aggregate', 'aggregate')
-                ->justify('right')
-                ->sortable();
+            $groupByLabel = $this->findElementByKey($this->availableColumns(), $this->groupBy)['label'] ?? $this->groupBy;
+
+            return [
+                Column::make($groupByLabel, 'group_value')->sortable(),
+                Column::make("{$this->aggregateFunction}({$this->aggregateColumn})", 'aggregate')
+                    ->justify('right')
+                    ->sortable(),
+            ];
         }
 
         return $columns;