added more tests for balance

internal/interpreter/batch_balances_query.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/formancehq/numscript/internal/parser"
 	"github.com/formancehq/numscript/internal/utils"
+	"golang.org/x/exp/maps"
 )
 
 // traverse the script to batch in advance required balance queries
@@ -56,7 +57,28 @@ func (st *programState) batchQuery(account string, asset string) {
 }
 
 func (st *programState) runBalancesQuery() error {
-	balances, err := st.Store.GetBalances(st.ctx, st.CurrentBalanceQuery)
+	filteredQuery := BalanceQuery{}
+	for accountName, queriedCurrencies := range st.CurrentBalanceQuery {
+
+		cachedCurrenciesForAccount := defaultMapGet(st.CachedBalances, accountName, func() AccountBalance {
+			return AccountBalance{}
+		})
+
+		for _, queriedCurrency := range queriedCurrencies {
+			isAlreadyCached := slices.Contains(maps.Keys(cachedCurrenciesForAccount), queriedCurrency)
+			if !isAlreadyCached {
+				filteredQuery[accountName] = queriedCurrencies
+			}
+		}
+
+	}
+
+	// avoid updating balances if we don't need to fetch new data
+	if len(filteredQuery) == 0 {
+		return nil
+	}
+
+	balances, err := st.Store.GetBalances(st.ctx, filteredQuery)
 	if err != nil {
 		return err
 	}

internal/interpreter/interpreter_test.go

@@ -2657,3 +2657,29 @@ func TestCascadingSources(t *testing.T) {
 	}
 	test(t, tc)
 }
+
+func TestUseBalanceTwice(t *testing.T) {
+	tc := NewTestCase()
+	tc.compile(t, `
+	vars { monetary $v = balance(@src, COIN) }
+
+	send $v (
+		source = @src
+		destination = @dest
+	)`)
+
+	tc.setBalance("src", "COIN", 50)
+	tc.expected = CaseResult{
+
+		Postings: []Posting{
+			{
+				Asset:       "COIN",
+				Amount:      big.NewInt(50),
+				Source:      "src",
+				Destination: "dest",
+			},
+		},
+		Error: nil,
+	}
+	test(t, tc)
+}

numscript_test.go

@@ -136,6 +136,86 @@ func TestGetBalancesOverdraft(t *testing.T) {
 		store.GetBalancesCalls)
 }
 
+func TestDoNotFetchBalanceTwice(t *testing.T) {
+	parseResult := numscript.Parse(`vars { monetary $v = balance(@src, COIN) }
+
+	send $v (
+		source = @src
+		destination = @dest
+	)`)
+
+	store := ObservableStore{}
+	parseResult.Run(context.Background(), nil, &store)
+
+	require.Equal(t,
+		[]numscript.BalanceQuery{
+			{
+				"src": {"COIN"},
+			},
+		},
+		store.GetBalancesCalls,
+	)
+
+}
+
+func TestDoNotFetchBalanceTwice2(t *testing.T) {
+	// same test as before, but this time the second batch is not empty
+	parseResult := numscript.Parse(`vars { monetary $v = balance(@src1, COIN) }
+
+	send $v (
+		source = {
+			@src1
+			@src2
+		}
+		destination = @dest
+	)`)
+
+	store := ObservableStore{}
+	parseResult.Run(context.Background(), nil, &store)
+
+	require.Equal(t,
+		[]numscript.BalanceQuery{
+			{
+				"src1": {"COIN"},
+			},
+			{
+				"src2": {"COIN"},
+			},
+		},
+		store.GetBalancesCalls,
+	)
+
+}
+
+func TestDoNotFetchBalanceTwice3(t *testing.T) {
+	// same test as before, but this time the second batch requires a _different asset_
+	parseResult := numscript.Parse(`vars { monetary $eur_m = balance(@src, EUR/2) }
+
+	
+	send [USD/2 100] (
+		// note here we are fetching a different currency
+		source = @src
+		destination = @dest
+	)
+`)
+
+	store := ObservableStore{}
+	parseResult.Run(context.Background(), nil, &store)
+
+	require.Equal(t,
+		[]numscript.BalanceQuery{
+			{
+				"src": {"EUR/2"},
+			},
+			{
+				"src": {"USD/2"},
+			},
+		},
+		store.GetBalancesCalls,
+	)
+
+}
+
 func TestQueryBalanceErr(t *testing.T) {
 	parseResult := numscript.Parse(`send [COIN 100] (
 	source = @src