feat: loop over a matrix (#1767)

variables.go

@@ -271,9 +271,13 @@ func itemsFromFor(
 ) ([]any, []string, error) {
 	var keys []string // The list of keys to loop over (only if looping over a map)
 	var values []any  // The list of values to loop over
+	// Get the list from a matrix
+	if f.Matrix != nil {
+		return asAnySlice(product(f.Matrix)), nil, nil
+	}
 	// Get the list from the explicit for list
 	if len(f.List) > 0 {
-		values = f.List
+		return f.List, nil, nil
 	}
 	// Get the list from the task sources
 	if f.From == "sources" {
@@ -322,3 +326,46 @@ func itemsFromFor(
 	}
 	return values, keys, nil
 }
+
+// product generates the cartesian product of the input map of slices.
+func product(inputMap map[string][]any) []map[string]any {
+	if len(inputMap) == 0 {
+		return nil
+	}
+
+	// Extract the keys and corresponding slices
+	keys := make([]string, 0, len(inputMap))
+	slices := make([][]any, 0, len(inputMap))
+	for key, slice := range inputMap {
+		keys = append(keys, key)
+		slices = append(slices, slice)
+	}
+
+	// Start with an empty product result
+	result := []map[string]any{{}}
+
+	// Iterate over each slice in the slices
+	for i, slice := range slices {
+		var newResult []map[string]any
+
+		// For each combination in the current result
+		for _, combination := range result {
+			// Append each element from the current slice to the combinations
+			for _, item := range slice {
+				newComb := make(map[string]any, len(combination))
+				// Copy the existing combination
+				for k, v := range combination {
+					newComb[k] = v
+				}
+				// Add the current item with the corresponding key
+				newComb[keys[i]] = item
+				newResult = append(newResult, newComb)
+			}
+		}
+
+		// Update result with the new combinations
+		result = newResult
+	}
+
+	return result
+}