Strict/loose mode for free ORIGINAL_SCOPE_VARIABLES

Author: szuend

src/decode/decode.test.ts

@@ -217,4 +217,24 @@ describe("decode", () => {
 
     assertEquals(info.ranges, []);
   });
+
+  it("throws for free ORIGINAL_SCOPE_VARIABLES items in strict mode", () => {
+    const encoder = new ItemEncoder();
+    encoder.addUnsignedVLQs(Tag.ORIGINAL_SCOPE_VARIABLES);
+    encoder.addSignedVLQs(0, 1).finishItem();
+    const map = createMap(encoder.encode(), ["foo", "bar"]);
+
+    assertThrows(() => decode(map, { mode: DecodeMode.STRICT }));
+  });
+
+  it("ignores free ORIGINAL_SCOPE_VARIABLES items in loose mode", () => {
+    const encoder = new ItemEncoder();
+    encoder.addUnsignedVLQs(Tag.ORIGINAL_SCOPE_VARIABLES);
+    encoder.addSignedVLQs(0, 1).finishItem();
+    const map = createMap(encoder.encode(), ["foo", "bar"]);
+
+    const info = decode(map, { mode: DecodeMode.LOOSE });
+
+    assertEquals(info.scopes, []);
+  });
 });

src/decode/decode.ts

@@ -27,6 +27,8 @@ import { TokenIterator } from "../vlq.ts";
  * STRICT mode will throw in the following situations:
  *
  *   - Encountering ORIGINAL_SCOPE_END, or GENERATED_RANGE_END items that don't have matching *_START items.
+ *   - Encountering ORIGINAL_SCOPE_VARIABLES items outside a surrounding scope START/END.
+ *   - Encountering GENERATED_RANGE_BINDINGS items outside a surrounding range START/END.
  *   - Miss-matches between the number of variables in a scope vs the number of value expressions in the ranges.
  *   - Out-of-bound indices into the "names" array.
  */
@@ -121,9 +123,10 @@ class Decoder {
         case Tag.ORIGINAL_SCOPE_VARIABLES: {
           const scope = this.#scopeStack.at(-1);
           if (!scope) {
-            throw new Error(
+            this.#throwInStrictMode(
               "Encountered ORIGINAL_SCOPE_VARIABLES without surrounding ORIGINAL_SCOPE_START",
             );
+            continue;
           }
 
           for (const variableIdx of item.variableIdxs) {