Decode range definitions

Author: szuend

src/codec.ts

@@ -58,6 +58,7 @@ interface GeneratedRangeStartItem {
   flags: number;
   line?: number;
   column: number;
+  definitionIdx?: number;
 }
 
 interface GeneratedRangeEndItem {

src/decode/decode.ts

@@ -52,6 +52,9 @@ class Decoder {
   readonly #scopeStack: OriginalScope[] = [];
   readonly #rangeStack: GeneratedRange[] = [];
 
+  readonly #countToScope = new Map<number, OriginalScope>();
+  #scopeCounter = 0;
+
   constructor(scopes: string, names: string[]) {
     this.#encodedScopes = scopes;
     this.#names = names;
@@ -89,6 +92,7 @@ class Decoder {
           );
 
           this.#scopeStack.push(scope);
+          this.#countToScope.set(this.#scopeCounter++, scope);
           break;
         }
         case Tag.ORIGINAL_SCOPE_END: {
@@ -136,6 +140,14 @@ class Decoder {
             children: [],
           };
 
+          if (item.definitionIdx !== undefined) {
+            this.#rangeState.defScopeIdx += item.definitionIdx;
+            range.originalScope = this.#countToScope.get(
+              this.#rangeState.defScopeIdx,
+            );
+            // TODO: Maybe throw if the idx is invalid?
+          }
+
           this.#rangeStack.push(range);
           break;
         }
@@ -176,6 +188,8 @@ class Decoder {
 
     this.#scopes = [];
     this.#ranges = [];
+    this.#scopeCounter = 0;
+    this.#countToScope.clear();
 
     return info;
   }
@@ -223,12 +237,18 @@ class Decoder {
           const line = flags & GeneratedRangeFlags.HAS_LINE
             ? iter.nextUnsignedVLQ()
             : undefined;
+          const column = iter.nextUnsignedVLQ();
+
+          const definitionIdx = flags & GeneratedRangeFlags.HAS_DEFINITION
+            ? iter.nextSignedVLQ()
+            : undefined;
 
           yield {
             tag,
             flags,
             line,
-            column: iter.nextUnsignedVLQ(),
+            column,
+            definitionIdx,
           };
           break;
         }

src/roundtrip.test.ts

@@ -101,4 +101,23 @@ describe("round trip", () => {
 
     assertCodec(builder.build());
   });
+
+  it("handles a single GeneratedRange with a definition scope", () => {
+    builder.startScope(0, 0).endScope(10, 0).startRange(0, 0, { scope: 0 })
+      .endRange(0, 10);
+
+    assertCodec(builder.build());
+  });
+
+  it("handles multiple GeneratedRanges with different definition scopes", () => {
+    builder.startScope(0, 0).endScope(10, 0).startScope(0, 0).endScope(20, 0)
+      .startRange(0, 0)
+      .startRange(0, 10, { scope: 0 })
+      .endRange(0, 40)
+      .startRange(0, 50, { scope: 1 })
+      .endRange(0, 80)
+      .endRange(0, 100);
+
+    assertCodec(builder.build());
+  });
 });