allow past a zero credit balance when overage is on

credit_overage_test.go

@@ -0,0 +1,119 @@
+package rulesengine_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/schematichq/rulesengine"
+	"github.com/schematichq/rulesengine/null"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// SCHX-582: credit overage. With overage enabled on a credit, consumption
+// continues past a zero balance and accrues at a configured rate, so the balance
+// stops gating the check.
+//
+// These mirror credit_overage_tests in rulesengine-rust; the two engines must
+// agree (SCHY-515) for as long as both are in use.
+func TestCreditOverage(t *testing.T) {
+	ctx := context.Background()
+
+	const creditID = "test-credit-id"
+
+	companyWith := func(balance float64, overage *bool) *rulesengine.Company {
+		company := createTestCompany()
+		company.CreditBalances = map[string]float64{creditID: balance}
+		if overage != nil {
+			company.CreditOverageEnabled = map[string]bool{creditID: *overage}
+		}
+		return company
+	}
+
+	creditRule := func() *rulesengine.Rule {
+		rule := createTestRule()
+		condition := createTestCondition(rulesengine.ConditionTypeCredit)
+		condition.CreditID = null.Nullable(creditID)
+		condition.ConsumptionRate = null.Nullable(1.0)
+		rule.Conditions = []*rulesengine.Condition{condition}
+		return rule
+	}
+
+	matches := func(t *testing.T, company *rulesengine.Company) bool {
+		t.Helper()
+
+		result, err := rulesengine.NewRuleCheckService().Check(ctx, &rulesengine.CheckScope{
+			Company: company,
+			Rule:    creditRule(),
+		})
+		require.NoError(t, err)
+		return result.Match
+	}
+
+	// The existing hard stop, unchanged when nobody has opted in.
+	t.Run("denies at zero without overage", func(t *testing.T) {
+		assert.False(t, matches(t, companyWith(0, nil)))
+	})
+
+	t.Run("allows with balance", func(t *testing.T) {
+		assert.True(t, matches(t, companyWith(5, nil)))
+	})
+
+	// The point of the feature.
+	t.Run("allows past zero with overage enabled", func(t *testing.T) {
+		assert.True(t, matches(t, companyWith(0, null.Nullable(true))))
+	})
+
+	// A negative balance is legal (SCH-5103); overage is what makes it billable,
+	// and an already-overdrafted company must keep working.
+	t.Run("allows when already negative", func(t *testing.T) {
+		assert.True(t, matches(t, companyWith(-40, null.Nullable(true))))
+	})
+
+	// Explicitly false must behave exactly like absent, or switching the setting
+	// back off would not restore the hard stop.
+	t.Run("explicit false still denies", func(t *testing.T) {
+		assert.False(t, matches(t, companyWith(0, null.Nullable(false))))
+	})
+
+	// Overage is per credit: enabling it on one must not unblock another.
+	t.Run("does not leak across credits", func(t *testing.T) {
+		company := companyWith(0, null.Nullable(true))
+		company.CreditBalances["other-credit-id"] = 0
+
+		rule := createTestRule()
+		condition := createTestCondition(rulesengine.ConditionTypeCredit)
+		condition.CreditID = null.Nullable("other-credit-id")
+		condition.ConsumptionRate = null.Nullable(1.0)
+		rule.Conditions = []*rulesengine.Condition{condition}
+
+		result, err := rulesengine.NewRuleCheckService().Check(ctx, &rulesengine.CheckScope{
+			Company: company,
+			Rule:    rule,
+		})
+		require.NoError(t, err)
+		assert.False(t, result.Match, "the other credit has no overage and no balance")
+	})
+
+	// Overage has to beat the more specific branches too. A caller-supplied
+	// credit cost would otherwise re-impose the balance gate it short-circuits.
+	t.Run("overrides the credit cost option", func(t *testing.T) {
+		flag := createTestFlag()
+		// Pinned false: createTestFlag randomizes DefaultValue, and CheckFlag falls
+		// back to it when no rule matches — so a true default would let this pass
+		// without the rule ever matching.
+		flag.DefaultValue = false
+		flag.Rules = []*rulesengine.Rule{creditRule()}
+
+		result, err := rulesengine.CheckFlag(
+			ctx,
+			companyWith(0, null.Nullable(true)),
+			nil,
+			flag,
+			rulesengine.WithCreditCost(creditID, 25),
+		)
+		require.NoError(t, err)
+		assert.True(t, result.Value)
+	})
+}

models.go

@@ -169,17 +169,24 @@ type Company struct {
 	AccountID     string `json:"account_id"`
 	EnvironmentID string `json:"environment_id"`
 
-	BasePlanID        *string                        `json:"base_plan_id"`
-	BillingProductIDs JSONSlice[string]              `json:"billing_product_ids"`
-	CreditBalances    map[string]float64             `json:"credit_balances"`
-	Entitlements      JSONSlice[*FeatureEntitlement] `json:"entitlements,omitempty"`
-	Keys              map[string]string              `json:"keys"`
-	Metrics           CompanyMetricCollection        `json:"metrics"`
-	PlanIDs           JSONSlice[string]              `json:"plan_ids"`
-	PlanVersionIDs    JSONSlice[string]              `json:"plan_version_ids"`
-	Rules             JSONSlice[*Rule]               `json:"rules"`
-	Subscription      *Subscription                  `json:"subscription"`
-	Traits            JSONSlice[*Trait]              `json:"traits"`
+	BasePlanID        *string            `json:"base_plan_id"`
+	BillingProductIDs JSONSlice[string]  `json:"billing_product_ids"`
+	CreditBalances    map[string]float64 `json:"credit_balances"`
+	// CreditOverageEnabled is the per-credit overage opt-in (SCHX-582), keyed by
+	// billing credit ID — the same key CreditBalances uses. When true for a
+	// credit, consumption continues past a zero balance and accrues against an
+	// overage rate rather than being denied, so the balance stops gating the
+	// check. Absent or false is the historical behaviour, so a caller that does
+	// not send the field keeps hard-stopping at zero.
+	CreditOverageEnabled map[string]bool                `json:"credit_overage_enabled"`
+	Entitlements         JSONSlice[*FeatureEntitlement] `json:"entitlements,omitempty"`
+	Keys                 map[string]string              `json:"keys"`
+	Metrics              CompanyMetricCollection        `json:"metrics"`
+	PlanIDs              JSONSlice[string]              `json:"plan_ids"`
+	PlanVersionIDs       JSONSlice[string]              `json:"plan_version_ids"`
+	Rules                JSONSlice[*Rule]               `json:"rules"`
+	Subscription         *Subscription                  `json:"subscription"`
+	Traits               JSONSlice[*Trait]              `json:"traits"`
 
 	mu sync.Mutex `json:"-"` // mutex for thread safety
 }

rulecheck.go

@@ -147,6 +147,18 @@ func (s *RuleCheckService) checkCreditBalanceCondition(ctx context.Context, scop
 		}
 	}
 
+	// SCHX-582: with overage enabled the balance no longer gates the check —
+	// consumption continues past zero and accrues at the configured rate, so
+	// every branch below (all of which compare against the balance) would ask
+	// the wrong question. There is no cap in the current design, so once overage
+	// is on there is nothing further to compare against.
+	//
+	// Mirrors check_credit_balance_condition in rulesengine-rust; the two must
+	// agree (see SCHY-515) until the Go engine is retired.
+	if scope.Company.CreditOverageEnabled[*condition.CreditID] {
+		return true, nil
+	}
+
 	// Precedence on credit-balance conditions, most specific first. No
 	// options supplied falls through to the legacy single-unit check.
 	//   1. creditCost[credit_id]: caller-supplied per-call cost in credits;