Encode range definition

Author: szuend

src/codec.ts

@@ -26,6 +26,7 @@ export const enum OriginalScopeFlags {
 
 export const enum GeneratedRangeFlags {
   HAS_LINE = 0x1,
+  HAS_DEFINITION = 0x2,
 }
 
 export const EmptyItem = Symbol("empty item");

src/encode/encode.test.ts

@@ -71,9 +71,19 @@ describe("encode", () => {
     assertThrows(() => encode(info));
   });
 
-  it("throws when a rangees' end precedes the ranges' start", () => {
+  it("throws when a ranges' end precedes the ranges' start", () => {
     const info = builder.startRange(10, 0).endRange(0, 0).build();
 
     assertThrows(() => encode(info));
   });
+
+  it("throws when a ranges' definition scope has not known to the encoder", () => {
+    const scope = builder.startScope(0, 0).endScope(10, 0).lastScope()!;
+    const info = builder.startRange(0, 10).endRange(0, 20).build();
+
+    // Set the range's definition as a copy of `scope`.
+    info.ranges[0].originalScope = { ...scope };
+
+    assertThrows(() => encode(info));
+  });
 });

src/encode/encoder.ts

@@ -33,9 +33,11 @@ export class Encoder {
   readonly #scopeState = { ...DEFAULT_SCOPE_STATE };
   readonly #rangeState = { ...DEFAULT_RANGE_STATE };
   #encodedItems: string[] = [];
-
   #currentItem: string = "";
 
+  #scopeToCount = new Map<OriginalScope, number>();
+  #scopeCounter = 0;
+
   constructor(info: ScopeInfo, names: string[]) {
     this.#info = info;
     this.#names = names;
@@ -98,6 +100,8 @@ export class Encoder {
     if (encodedName !== undefined) this.#encodeSigned(encodedName);
     if (encodedKind !== undefined) this.#encodeSigned(encodedKind);
     this.#finishItem();
+
+    this.#scopeToCount.set(scope, this.#scopeCounter++);
   }
 
   #encodeOriginalScopeEnd(scope: OriginalScope) {
@@ -134,9 +138,24 @@ export class Encoder {
     this.#rangeState.line = line;
     this.#rangeState.column = column;
 
+    let encodedDefinition;
+    if (range.originalScope) {
+      const definitionIdx = this.#scopeToCount.get(range.originalScope);
+      if (definitionIdx === undefined) {
+        throw new Error("Unknown OriginalScope for definition!");
+      }
+
+      flags |= GeneratedRangeFlags.HAS_DEFINITION;
+
+      encodedDefinition = definitionIdx - this.#rangeState.defScopeIdx;
+      this.#rangeState.defScopeIdx = definitionIdx;
+    }
+
     this.#encodeTag(EncodedTag.GENERATED_RANGE_START).#encodeUnsigned(flags);
     if (encodedLine > 0) this.#encodeUnsigned(encodedLine);
-    this.#encodeUnsigned(encodedColumn).#finishItem();
+    this.#encodeUnsigned(encodedColumn);
+    if (encodedDefinition !== undefined) this.#encodeSigned(encodedDefinition);
+    this.#finishItem();
   }
 
   #encodeGeneratedRangeEnd(range: GeneratedRange) {