Fill empty months in history

nummi/main/views.py

@@ -34,18 +34,37 @@ from .forms import (
 from .models import Account, Category, Invoice, Snapshot, Transaction
 
 
+class GenerateMonth(models.Func):
+    function = "generate_series"
+    template = "%(function)s(%(expressions)s, '1 month')::date"
+
+
 def history(transaction_set):
-    _history = (
-        transaction_set.values(month=models.functions.TruncMonth("date"))
-        .annotate(
+    _transaction_month = transaction_set.values(
+        month=models.functions.TruncMonth("date")
+    ).order_by("-date")
+    _months = (
+        transaction_set.values(
+            month=GenerateMonth(
+                _transaction_month.last()["month"],
+                models.functions.Now(output_field=models.DateField()),
+            )
+        )
+        .annotate(sum_m=models.Value(0), sum_p=models.Value(0), sum=models.Value(0))
+        .difference(
+            _transaction_month.annotate(
+                sum_m=models.Value(0), sum_p=models.Value(0), sum=models.Value(0)
+            )
+        )
+    )
+    _history = _transaction_month.annotate(
         sum_p=models.Sum("value", filter=models.Q(value__gt=0)),
         sum_m=models.Sum("value", filter=models.Q(value__lt=0)),
         sum=models.Sum("value"),
-        )
-        .order_by("-month")
-    )
+    ).order_by("-month")
+
     return {
-        "data": _history,
+        "data": _history.union(_months).order_by("-month"),
         "max": max(
             _history.aggregate(
                 max=models.Max("sum_p", default=0),