fix(eval_query): stabilize eval zero behavior and property test

Agent-Logs-Url: https://github.com/githubnext/tsessebe/sessions/86da2f84-1920-4e7c-b7bd-edc31603939f

Co-authored-by: mrjf <180956+mrjf@users.noreply.github.com>

Author: Copilot

src/stats/eval_query.ts

@@ -446,7 +446,7 @@ function numericCmp(l: Scalar, r: Scalar): number {
 
 function numericOp(l: Scalar, r: Scalar, fn: (a: number, b: number) => number): Scalar {
   if (l == null || r == null) return null;
-  if (typeof l === "number" && typeof r === "number") return fn(l, r);
+  if (typeof l === "number" && typeof r === "number") return canonicalizeZero(fn(l, r));
   return null;
 }
 
@@ -471,10 +471,14 @@ function applyBinOp(op: string, l: Scalar, r: Scalar): Scalar {
 function addScalar(l: Scalar, r: Scalar): Scalar {
   if (l == null || r == null) return null;
   if (typeof l === "string" || typeof r === "string") return String(l) + String(r);
-  if (typeof l === "number" && typeof r === "number") return l + r;
+  if (typeof l === "number" && typeof r === "number") return canonicalizeZero(l + r);
   return null;
 }
 
+function canonicalizeZero(value: number): number {
+  return Object.is(value, -0) ? 0 : value;
+}
+
 function evalInOp(node: Extract<AstNode, { type: "InOp" }>, row: ReadonlyMap<string, Scalar>): boolean {
   const val = evalNode(node.value, row);
   const found = node.list.some((item) => scalarEq(val, evalNode(item, row)));

tests/stats/eval_query.test.ts

@@ -364,7 +364,7 @@ describe("evalDataFrame", () => {
   it("eval('a * 0') is all zeros", () => {
     fc.assert(
       fc.property(
-        fc.array(fc.float({ noNaN: true }), { minLength: 1, maxLength: 10 }),
+        fc.array(fc.float({ noNaN: true, min: -1e6, max: 1e6 }), { minLength: 1, maxLength: 10 }),
         (values) => {
           const df = DataFrame.fromArrays({ a: values });
           const result = evalDataFrame(df, "a * 0");