fix: report "Division by zero." for modulo by zero

sjsonnet/src/sjsonnet/Evaluator.scala

@@ -245,7 +245,7 @@ class Evaluator(
         if (rd == 0) null
         else { val r = ld / rd; if (r.isInfinite) null else Val.cachedNum(pos, r) }
       case Expr.BinaryOp.OP_% =>
-        Val.cachedNum(pos, ld % rd)
+        if (rd == 0) null else Val.cachedNum(pos, ld % rd)
       case Expr.BinaryOp.OP_+ =>
         val r = ld + rd; if (r.isInfinite) null else Val.cachedNum(pos, r)
       case Expr.BinaryOp.OP_- =>
@@ -719,7 +719,9 @@ class Evaluator(
         val r = ld / rd
         if (r.isInfinite) Error.fail("overflow", pos)
         Val.cachedNum(pos, r)
-      case Expr.BinaryOp.OP_% => Val.cachedNum(pos, ld % rd)
+      case Expr.BinaryOp.OP_% =>
+        if (rd == 0) Error.fail("Division by zero.", pos)
+        Val.cachedNum(pos, ld % rd)
       // Use position-free static singletons for boolean results — this method is only called
       // from comprehension fast paths where position info on boolean results is unnecessary.
       // Avoids 1 object allocation per comparison in inner loops (significant for 1M+ iterations).
@@ -862,7 +864,10 @@ class Evaluator(
         val result = l / r
         if (result.isInfinite) Error.fail("overflow", pos); result
       case Expr.BinaryOp.OP_% =>
-        visitExprAsDouble(e.lhs) % visitExprAsDouble(e.rhs)
+        val l = visitExprAsDouble(e.lhs)
+        val r = visitExprAsDouble(e.rhs)
+        if (r == 0) Error.fail("Division by zero.", pos)
+        l % r
       case Expr.BinaryOp.OP_+ =>
         val r = visitExprAsDouble(e.lhs) + visitExprAsDouble(e.rhs)
         if (r.isInfinite) Error.fail("overflow", pos); r
@@ -1342,8 +1347,10 @@ class Evaluator(
         l match {
           case Val.Num(_, ld) =>
             r match {
-              case Val.Num(_, rd) => Val.cachedNum(pos, ld % rd)
-              case _              => failBinOp(l, e.op, r, pos)
+              case Val.Num(_, rd) =>
+                if (rd == 0) Error.fail("Division by zero.", pos)
+                Val.cachedNum(pos, ld % rd)
+              case _ => failBinOp(l, e.op, r, pos)
             }
           case ls: Val.Str => Format.format(ls.str, r, pos)
           case _           => failBinOp(l, e.op, r, pos)

sjsonnet/src/sjsonnet/StaticOptimizer.scala

@@ -187,7 +187,7 @@ class StaticOptimizer(
             case BinaryOp.OP_/ =>
               if (r == 0) return Double.NaN
               val res = l / r; if (res.isInfinite) return Double.NaN; res
-            case BinaryOp.OP_%  => l % r
+            case BinaryOp.OP_%  => if (r == 0) return Double.NaN; l % r
             case BinaryOp.OP_<< =>
               val ll = l.toSafeLong(pos)(ev); val rr = r.toSafeLong(pos)(ev)
               if (rr < 0) return Double.NaN
@@ -480,8 +480,8 @@ class StaticOptimizer(
           }
         case BinaryOp.OP_% =>
           (lhs, rhs) match {
-            case (Val.Num(_, l), Val.Num(_, r)) => Val.Num(pos, l % r)
-            case _                              => fallback
+            case (Val.Num(_, l), Val.Num(_, r)) if r != 0 => Val.Num(pos, l % r)
+            case _                                        => fallback
           }
         case BinaryOp.OP_< =>
           tryFoldComparison(pos, lhs, BinaryOp.OP_<, rhs, fallback)

sjsonnet/src/sjsonnet/stdlib/MathModule.scala

@@ -254,8 +254,10 @@ object MathModule extends AbstractFunctionModule {
       new Val.Builtin2("mod", "a", "b") {
         def evalRhs(a: Eval, b: Eval, ev: EvalScope, pos: Position): Val = {
           (a.value, b.value) match {
-            case (x: Val.Num, y: Val.Num) => Val.cachedNum(pos, x.asDouble % y.asDouble)
-            case _                        => Format.format(a.value.asString, b.value, pos)(ev)
+            case (x: Val.Num, y: Val.Num) =>
+              if (y.asDouble == 0) Error.fail("Division by zero.", pos)(ev)
+              Val.cachedNum(pos, x.asDouble % y.asDouble)
+            case _ => Format.format(a.value.asString, b.value, pos)(ev)
           }
         }
       }
@@ -268,6 +270,7 @@ object MathModule extends AbstractFunctionModule {
      * Performs modulo arithmetic for numeric values.
      */
     builtin("modulo", "a", "b") { (pos, ev, a: Double, b: Double) =>
+      if (b == 0) Error.fail("Division by zero.", pos)(ev)
       a % b
     },
     /**

sjsonnet/test/resources/go_test_suite/percent_mod_int5.jsonnet.golden

@@ -1,3 +1,3 @@
-sjsonnet.Error: not a number
+sjsonnet.Error: Division by zero.
     at [<root>].(percent_mod_int5.jsonnet:1:4)
 

sjsonnet/test/resources/new_test_suite/error.modulo_by_zero.jsonnet

@@ -0,0 +1,2 @@
+// Modulo by zero must report "Division by zero." matching go-jsonnet behavior.
+1 % 0

sjsonnet/test/resources/new_test_suite/error.modulo_by_zero.jsonnet.golden

@@ -0,0 +1,2 @@
+sjsonnet.Error: Division by zero.
+    at [<root>].(error.modulo_by_zero.jsonnet:2:3)

sjsonnet/test/resources/new_test_suite/error.modulo_by_zero_runtime.jsonnet

@@ -0,0 +1,4 @@
+// Runtime modulo by zero (non-constant operands) must also report "Division by zero."
+local x = 10;
+local y = 0;
+x % y

sjsonnet/test/resources/new_test_suite/error.modulo_by_zero_runtime.jsonnet.golden

@@ -0,0 +1 @@
+sjsonnet.Error: Division by zero.