fix(vnext): reject invalid CTE cursor positions

Author: Light2Dark

src/vnext/__tests__/cte-layout.test.ts

@@ -1180,9 +1180,17 @@ describe("bounded CTE layout", () => {
         names: [{ quoted: false, value: "outer_cte" }],
       },
     });
-    for (const position of [-1, Number.NaN, text.length + 1]) {
+    for (const position of [
+      -1,
+      0.5,
+      text.length - 0.5,
+      Number.NaN,
+      Number.POSITIVE_INFINITY,
+      text.length + 1,
+    ]) {
       expect(visibleSqlCtesAt(layout, position)).toMatchObject({
         ctes: [],
+        issues: [],
         quality: "recovered",
         shadowing: { coverage: "unknown" },
       });

src/vnext/cte-layout.ts

@@ -1602,6 +1602,18 @@ export function visibleSqlCtesAt(
   layout: Exclude<SqlCteLayout, { status: "unavailable" }>,
   position: number,
 ): SqlCteVisibility {
+  if (
+    !Number.isSafeInteger(position) ||
+    position < 0 ||
+    position > layout.statementLength
+  ) {
+    return Object.freeze({
+      ctes: Object.freeze([]),
+      issues: Object.freeze([]),
+      quality: "recovered",
+      shadowing: Object.freeze({ coverage: "unknown" }),
+    });
+  }
   const namespace = new Map<
     number,
     SqlCteDeclaration | null
@@ -1612,11 +1624,7 @@ export function visibleSqlCtesAt(
     position > layout.exactThrough ||
     (position === layout.exactThrough &&
       layout.exactThrough < layout.statementLength);
-  let shadowingUnknown =
-    !Number.isSafeInteger(position) ||
-    position < 0 ||
-    position > layout.statementLength ||
-    beyondExactCoverage;
+  let shadowingUnknown = beyondExactCoverage;
 
   if (beyondExactCoverage) {
     for (const issue of layout.issues) {