Implement encoding of sub-range bindings

Author: szuend

src/codec.ts

@@ -9,6 +9,7 @@ export const enum Tag {
   GENERATED_RANGE_START = 0x4,
   GENERATED_RANGE_END = 0x5,
   GENERATED_RANGE_BINDINGS = 0x6,
+  GENERATED_RANGE_SUBRANGE_BINDING = 0x7,
   GENERATED_RANGE_CALL_SITE = 0x8,
 }
 
@@ -19,6 +20,7 @@ export const enum EncodedTag {
   GENERATED_RANGE_START = "E", // 0x4
   GENERATED_RANGE_END = "F", // 0x5
   GENERATED_RANGE_BINDINGS = "G", // 0x6
+  GENERATED_RANGE_SUBRANGE_BINDING = "H", // 0x7
   GENERATED_RANGE_CALL_SITE = "I", // 0x8
 }
 

src/encode/encode.test.ts

@@ -107,4 +107,36 @@ describe("encode", () => {
 
     assertThrows(() => encode(info));
   });
+
+  it("throws when sub-range bindings are not sorted", () => {
+    const info = builder.startScope(0, 0, { key: "key", variables: ["a"] })
+      .endScope(10, 0).startRange(0, 0, {
+        scopeKey: "key",
+        values: [[{
+          from: { line: 5, column: 0 },
+          to: { line: 10, column: 0 },
+        }, {
+          from: { line: 0, column: 0 },
+          to: { line: 5, column: 0 },
+        }]],
+      }).endRange(10, 0).build();
+
+    assertThrows(() => encode(info));
+  });
+
+  it("throws when sub-range bindings have a gap", () => {
+    const info = builder.startScope(0, 0, { key: "key", variables: ["a"] })
+      .endScope(10, 0).startRange(0, 0, {
+        scopeKey: "key",
+        values: [[{
+          from: { line: 0, column: 0 },
+          to: { line: 4, column: 0 },
+        }, {
+          from: { line: 5, column: 0 },
+          to: { line: 10, column: 0 },
+        }]],
+      }).endRange(10, 0).build();
+
+    assertThrows(() => encode(info));
+  });
 });

src/encode/encoder.ts

@@ -9,6 +9,7 @@ import {
 } from "../codec.ts";
 import type { GeneratedRange, OriginalScope, ScopeInfo } from "../scopes.d.ts";
 import { encodeSigned, encodeUnsigned } from "../vlq.ts";
+import { comparePositions } from "../util.ts";
 
 const DEFAULT_SCOPE_STATE = {
   line: 0,
@@ -147,6 +148,7 @@ export class Encoder {
   #encodeGeneratedRange(range: GeneratedRange): void {
     this.#encodeGeneratedRangeStart(range);
     this.#encodeGeneratedRangeBindings(range);
+    this.#encodeGeneratedRangeSubRangeBindings(range);
     this.#encodeGeneratedRangeCallSite(range);
     range.children.forEach((child) => this.#encodeGeneratedRange(child));
     this.#encodeGeneratedRangeEnd(range);
@@ -190,6 +192,49 @@ export class Encoder {
     this.#finishItem();
   }
 
+  #encodeGeneratedRangeSubRangeBindings(range: GeneratedRange) {
+    if (range.values.length === 0) return;
+
+    for (let i = 0; i < range.values.length; ++i) {
+      const value = range.values[i];
+      if (!Array.isArray(value) || value.length <= 1) {
+        continue;
+      }
+
+      this.#encodeTag(EncodedTag.GENERATED_RANGE_SUBRANGE_BINDING)
+        .#encodeUnsigned(i);
+
+      let lastLine = range.start.line;
+      let lastColumn = range.start.column;
+      for (let j = 1; j < value.length; ++j) {
+        const subRange = value[j];
+        const prevSubRange = value[j - 1];
+
+        if (comparePositions(prevSubRange.to, subRange.from) !== 0) {
+          throw new Error("Sub-range bindings must not have gaps");
+        }
+
+        const encodedLine = subRange.from.line - lastLine;
+        const encodedColumn = encodedLine === 0
+          ? subRange.from.column - lastColumn
+          : subRange.from.column;
+        if (encodedLine < 0 || encodedColumn < 0) {
+          throw new Error("Sub-range bindings must be sorted");
+        }
+
+        lastLine = subRange.from.line;
+        lastColumn = subRange.from.column;
+
+        const binding = subRange.value === undefined
+          ? 0
+          : this.#resolveNamesIdx(subRange.value) + 1;
+        this.#encodeUnsigned(binding).#encodeUnsigned(encodedLine)
+          .#encodeUnsigned(encodedColumn);
+      }
+      this.#finishItem();
+    }
+  }
+
   #encodeGeneratedRangeBindings(range: GeneratedRange) {
     if (range.values.length === 0) return;
 
@@ -203,12 +248,16 @@ export class Encoder {
 
     this.#encodeTag(EncodedTag.GENERATED_RANGE_BINDINGS);
     for (const val of range.values) {
-      if (val === null || val == undefined) {
+      if (val === null || val === undefined) {
         this.#encodeUnsigned(0);
       } else if (typeof val === "string") {
         this.#encodeUnsigned(this.#resolveNamesIdx(val) + 1);
       } else {
-        throw new Error("Sub-range bindings not implemented yet!");
+        const initialValue = val[0];
+        const binding = initialValue.value === undefined
+          ? 0
+          : this.#resolveNamesIdx(initialValue.value) + 1;
+        this.#encodeUnsigned(binding);
       }
     }
     this.#finishItem();