fix: Associate sub-range bindings with the correct range

Fixes #1

Author: szuend

src/decode/decode.ts

@@ -127,7 +127,10 @@ class Decoder {
   readonly #rangeStack: GeneratedRange[] = [];
 
   #flatOriginalScopes: OriginalScope[] = [];
-  #subRangeBindingsForRange = new Map<number, [number, number, number][]>();
+  #subRangeBindingsForRange = new Map<
+    GeneratedRange,
+    Map<number, [number, number, number][]>
+  >();
 
   constructor(scopes: string, names: string[], options: DecodeOptions) {
     this.#encodedScopes = scopes;
@@ -403,7 +406,6 @@ class Decoder {
     }
 
     this.#rangeStack.push(range);
-    this.#subRangeBindingsForRange.clear();
   }
 
   #handleGeneratedRangeBindingsItem(valueIdxs: number[]) {
@@ -428,13 +430,25 @@ class Decoder {
     variableIndex: number,
     bindings: [number, number, number][],
   ) {
-    if (this.#subRangeBindingsForRange.has(variableIndex)) {
+    const range = this.#rangeStack.at(-1);
+    if (!range) {
+      this.#throwInStrictMode(
+        "Encountered GENERATED_RANGE_SUBRANGE_BINDING without surrounding GENERATED_RANGE_START",
+      );
+      return;
+    }
+    let subRangeBindings = this.#subRangeBindingsForRange.get(range);
+    if (!subRangeBindings) {
+      subRangeBindings = new Map();
+      this.#subRangeBindingsForRange.set(range, subRangeBindings);
+    }
+    if (subRangeBindings.has(variableIndex)) {
       this.#throwInStrictMode(
         "Encountered multiple GENERATED_RANGE_SUBRANGE_BINDING items for the same variable",
       );
       return;
     }
-    this.#subRangeBindingsForRange.set(variableIndex, bindings);
+    subRangeBindings.set(variableIndex, bindings);
   }
 
   #handleGeneratedRangeCallSite(
@@ -490,7 +504,10 @@ class Decoder {
   }
 
   #handleGeneratedRangeSubRangeBindings(range: GeneratedRange) {
-    for (const [variableIndex, bindings] of this.#subRangeBindingsForRange) {
+    const subRangeBindings = this.#subRangeBindingsForRange.get(range);
+    if (!subRangeBindings) return;
+
+    for (const [variableIndex, bindings] of subRangeBindings) {
       const value = range.values[variableIndex];
       const subRanges: SubRangeBinding[] = [];
       range.values[variableIndex] = subRanges;

src/roundtrip.test.ts

@@ -269,4 +269,24 @@ describe("round trip", () => {
 
     assertCodec(builder.build());
   });
+
+  // Regression test for issue #1.
+  it("handles sub-ranges correctly when the range has children", () => {
+    builder.startScope(0, 0, { variables: ["x"], key: "root" }).endScope(1, 19)
+      .startRange(0, 0, {
+        scopeKey: "root",
+        values: [[{
+          from: { line: 0, column: 0 },
+          to: { line: 1, column: 0 },
+          value: '"foo"',
+        }, {
+          from: { line: 1, column: 0 },
+          to: { line: 1, column: 19 },
+          value: '"bar"',
+        }]],
+      }).startRange(0, 5)
+      .endRange(0, 10).endRange(1, 19);
+
+    assertCodec(builder.build());
+  });
 });