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diff --git a/node_modules/@bcoe/v8-coverage/src/lib/merge.ts b/node_modules/@bcoe/v8-coverage/src/lib/merge.ts
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+++ b/node_modules/@bcoe/v8-coverage/src/lib/merge.ts
@@ -0,0 +1,343 @@
+import {
+  deepNormalizeScriptCov,
+  normalizeFunctionCov,
+  normalizeProcessCov,
+  normalizeRangeTree,
+  normalizeScriptCov,
+} from "./normalize";
+import { RangeTree } from "./range-tree";
+import { FunctionCov, ProcessCov, Range, RangeCov, ScriptCov } from "./types";
+
+/**
+ * Merges a list of process coverages.
+ *
+ * The result is normalized.
+ * The input values may be mutated, it is not safe to use them after passing
+ * them to this function.
+ * The computation is synchronous.
+ *
+ * @param processCovs Process coverages to merge.
+ * @return Merged process coverage.
+ */
+export function mergeProcessCovs(processCovs: ReadonlyArray<ProcessCov>): ProcessCov {
+  if (processCovs.length === 0) {
+    return {result: []};
+  }
+
+  const urlToScripts: Map<string, ScriptCov[]> = new Map();
+  for (const processCov of processCovs) {
+    for (const scriptCov of processCov.result) {
+      let scriptCovs: ScriptCov[] | undefined = urlToScripts.get(scriptCov.url);
+      if (scriptCovs === undefined) {
+        scriptCovs = [];
+        urlToScripts.set(scriptCov.url, scriptCovs);
+      }
+      scriptCovs.push(scriptCov);
+    }
+  }
+
+  const result: ScriptCov[] = [];
+  for (const scripts of urlToScripts.values()) {
+    // assert: `scripts.length > 0`
+    result.push(mergeScriptCovs(scripts)!);
+  }
+  const merged: ProcessCov = {result};
+
+  normalizeProcessCov(merged);
+  return merged;
+}
+
+/**
+ * Merges a list of matching script coverages.
+ *
+ * Scripts are matching if they have the same `url`.
+ * The result is normalized.
+ * The input values may be mutated, it is not safe to use them after passing
+ * them to this function.
+ * The computation is synchronous.
+ *
+ * @param scriptCovs Process coverages to merge.
+ * @return Merged script coverage, or `undefined` if the input list was empty.
+ */
+export function mergeScriptCovs(scriptCovs: ReadonlyArray<ScriptCov>): ScriptCov | undefined {
+  if (scriptCovs.length === 0) {
+    return undefined;
+  } else if (scriptCovs.length === 1) {
+    const merged: ScriptCov = scriptCovs[0];
+    deepNormalizeScriptCov(merged);
+    return merged;
+  }
+
+  const first: ScriptCov = scriptCovs[0];
+  const scriptId: string = first.scriptId;
+  const url: string = first.url;
+
+  const rangeToFuncs: Map<string, FunctionCov[]> = new Map();
+  for (const scriptCov of scriptCovs) {
+    for (const funcCov of scriptCov.functions) {
+      const rootRange: string = stringifyFunctionRootRange(funcCov);
+      let funcCovs: FunctionCov[] | undefined = rangeToFuncs.get(rootRange);
+
+      if (funcCovs === undefined ||
+        // if the entry in rangeToFuncs is function-level granularity and
+        // the new coverage is block-level, prefer block-level.
+        (!funcCovs[0].isBlockCoverage && funcCov.isBlockCoverage)) {
+        funcCovs = [];
+        rangeToFuncs.set(rootRange, funcCovs);
+      } else if (funcCovs[0].isBlockCoverage && !funcCov.isBlockCoverage) {
+        // if the entry in rangeToFuncs is block-level granularity, we should
+        // not append function level granularity.
+        continue;
+      }
+      funcCovs.push(funcCov);
+    }
+  }
+
+  const functions: FunctionCov[] = [];
+  for (const funcCovs of rangeToFuncs.values()) {
+    // assert: `funcCovs.length > 0`
+    functions.push(mergeFunctionCovs(funcCovs)!);
+  }
+
+  const merged: ScriptCov = {scriptId, url, functions};
+  normalizeScriptCov(merged);
+  return merged;
+}
+
+/**
+ * Returns a string representation of the root range of the function.
+ *
+ * This string can be used to match function with same root range.
+ * The string is derived from the start and end offsets of the root range of
+ * the function.
+ * This assumes that `ranges` is non-empty (true for valid function coverages).
+ *
+ * @param funcCov Function coverage with the range to stringify
+ * @internal
+ */
+function stringifyFunctionRootRange(funcCov: Readonly<FunctionCov>): string {
+  const rootRange: RangeCov = funcCov.ranges[0];
+  return `${rootRange.startOffset.toString(10)};${rootRange.endOffset.toString(10)}`;
+}
+
+/**
+ * Merges a list of matching function coverages.
+ *
+ * Functions are matching if their root ranges have the same span.
+ * The result is normalized.
+ * The input values may be mutated, it is not safe to use them after passing
+ * them to this function.
+ * The computation is synchronous.
+ *
+ * @param funcCovs Function coverages to merge.
+ * @return Merged function coverage, or `undefined` if the input list was empty.
+ */
+export function mergeFunctionCovs(funcCovs: ReadonlyArray<FunctionCov>): FunctionCov | undefined {
+  if (funcCovs.length === 0) {
+    return undefined;
+  } else if (funcCovs.length === 1) {
+    const merged: FunctionCov = funcCovs[0];
+    normalizeFunctionCov(merged);
+    return merged;
+  }
+
+  const functionName: string = funcCovs[0].functionName;
+
+  const trees: RangeTree[] = [];
+  for (const funcCov of funcCovs) {
+    // assert: `fn.ranges.length > 0`
+    // assert: `fn.ranges` is sorted
+    trees.push(RangeTree.fromSortedRanges(funcCov.ranges)!);
+  }
+
+  // assert: `trees.length > 0`
+  const mergedTree: RangeTree = mergeRangeTrees(trees)!;
+  normalizeRangeTree(mergedTree);
+  const ranges: RangeCov[] = mergedTree.toRanges();
+  const isBlockCoverage: boolean = !(ranges.length === 1 && ranges[0].count === 0);
+
+  const merged: FunctionCov = {functionName, ranges, isBlockCoverage};
+  // assert: `merged` is normalized
+  return merged;
+}
+
+/**
+ * @precondition Same `start` and `end` for all the trees
+ */
+function mergeRangeTrees(trees: ReadonlyArray<RangeTree>): RangeTree | undefined {
+  if (trees.length <= 1) {
+    return trees[0];
+  }
+  const first: RangeTree = trees[0];
+  let delta: number = 0;
+  for (const tree of trees) {
+    delta += tree.delta;
+  }
+  const children: RangeTree[] = mergeRangeTreeChildren(trees);
+  return new RangeTree(first.start, first.end, delta, children);
+}
+
+class RangeTreeWithParent {
+  readonly parentIndex: number;
+  readonly tree: RangeTree;
+
+  constructor(parentIndex: number, tree: RangeTree) {
+    this.parentIndex = parentIndex;
+    this.tree = tree;
+  }
+}
+
+class StartEvent {
+  readonly offset: number;
+  readonly trees: RangeTreeWithParent[];
+
+  constructor(offset: number, trees: RangeTreeWithParent[]) {
+    this.offset = offset;
+    this.trees = trees;
+  }
+
+  static compare(a: StartEvent, b: StartEvent): number {
+    return a.offset - b.offset;
+  }
+}
+
+class StartEventQueue {
+  private readonly queue: StartEvent[];
+  private nextIndex: number;
+  private pendingOffset: number;
+  private pendingTrees: RangeTreeWithParent[] | undefined;
+
+  private constructor(queue: StartEvent[]) {
+    this.queue = queue;
+    this.nextIndex = 0;
+    this.pendingOffset = 0;
+    this.pendingTrees = undefined;
+  }
+
+  static fromParentTrees(parentTrees: ReadonlyArray<RangeTree>): StartEventQueue {
+    const startToTrees: Map<number, RangeTreeWithParent[]> = new Map();
+    for (const [parentIndex, parentTree] of parentTrees.entries()) {
+      for (const child of parentTree.children) {
+        let trees: RangeTreeWithParent[] | undefined = startToTrees.get(child.start);
+        if (trees === undefined) {
+          trees = [];
+          startToTrees.set(child.start, trees);
+        }
+        trees.push(new RangeTreeWithParent(parentIndex, child));
+      }
+    }
+    const queue: StartEvent[] = [];
+    for (const [startOffset, trees] of startToTrees) {
+      queue.push(new StartEvent(startOffset, trees));
+    }
+    queue.sort(StartEvent.compare);
+    return new StartEventQueue(queue);
+  }
+
+  setPendingOffset(offset: number): void {
+    this.pendingOffset = offset;
+  }
+
+  pushPendingTree(tree: RangeTreeWithParent): void {
+    if (this.pendingTrees === undefined) {
+      this.pendingTrees = [];
+    }
+    this.pendingTrees.push(tree);
+  }
+
+  next(): StartEvent | undefined {
+    const pendingTrees: RangeTreeWithParent[] | undefined = this.pendingTrees;
+    const nextEvent: StartEvent | undefined = this.queue[this.nextIndex];
+    if (pendingTrees === undefined) {
+      this.nextIndex++;
+      return nextEvent;
+    } else if (nextEvent === undefined) {
+      this.pendingTrees = undefined;
+      return new StartEvent(this.pendingOffset, pendingTrees);
+    } else {
+      if (this.pendingOffset < nextEvent.offset) {
+        this.pendingTrees = undefined;
+        return new StartEvent(this.pendingOffset, pendingTrees);
+      } else {
+        if (this.pendingOffset === nextEvent.offset) {
+          this.pendingTrees = undefined;
+          for (const tree of pendingTrees) {
+            nextEvent.trees.push(tree);
+          }
+        }
+        this.nextIndex++;
+        return nextEvent;
+      }
+    }
+  }
+}
+
+function mergeRangeTreeChildren(parentTrees: ReadonlyArray<RangeTree>): RangeTree[] {
+  const result: RangeTree[] = [];
+  const startEventQueue: StartEventQueue = StartEventQueue.fromParentTrees(parentTrees);
+  const parentToNested: Map<number, RangeTree[]> = new Map();
+  let openRange: Range | undefined;
+
+  while (true) {
+    const event: StartEvent | undefined = startEventQueue.next();
+    if (event === undefined) {
+      break;
+    }
+
+    if (openRange !== undefined && openRange.end <= event.offset) {
+      result.push(nextChild(openRange, parentToNested));
+      openRange = undefined;
+    }
+
+    if (openRange === undefined) {
+      let openRangeEnd: number = event.offset + 1;
+      for (const {parentIndex, tree} of event.trees) {
+        openRangeEnd = Math.max(openRangeEnd, tree.end);
+        insertChild(parentToNested, parentIndex, tree);
+      }
+      startEventQueue.setPendingOffset(openRangeEnd);
+      openRange = {start: event.offset, end: openRangeEnd};
+    } else {
+      for (const {parentIndex, tree} of event.trees) {
+        if (tree.end > openRange.end) {
+          const right: RangeTree = tree.split(openRange.end);
+          startEventQueue.pushPendingTree(new RangeTreeWithParent(parentIndex, right));
+        }
+        insertChild(parentToNested, parentIndex, tree);
+      }
+    }
+  }
+  if (openRange !== undefined) {
+    result.push(nextChild(openRange, parentToNested));
+  }
+
+  return result;
+}
+
+function insertChild(parentToNested: Map<number, RangeTree[]>, parentIndex: number, tree: RangeTree): void {
+  let nested: RangeTree[] | undefined = parentToNested.get(parentIndex);
+  if (nested === undefined) {
+    nested = [];
+    parentToNested.set(parentIndex, nested);
+  }
+  nested.push(tree);
+}
+
+function nextChild(openRange: Range, parentToNested: Map<number, RangeTree[]>): RangeTree {
+  const matchingTrees: RangeTree[] = [];
+
+  for (const nested of parentToNested.values()) {
+    if (nested.length === 1 && nested[0].start === openRange.start && nested[0].end === openRange.end) {
+      matchingTrees.push(nested[0]);
+    } else {
+      matchingTrees.push(new RangeTree(
+        openRange.start,
+        openRange.end,
+        0,
+        nested,
+      ));
+    }
+  }
+  parentToNested.clear();
+  return mergeRangeTrees(matchingTrees)!;
+}