fix: optimize diff deduplication- use reference identity when diffs are from the same document pair

Author: b41ex

src/components/compare/compare.operations.ts

@@ -140,14 +140,18 @@ async function compareCurrentApiType(
   const operationsMap = createPairOperationsMap(previousGroupSlug, currentGroupSlug, prevOperationsWithPrefix, currOperationsWithPrefix, apiBuilder)
   const operationPairs = Object.values(operationsMap)
   const pairedDocs = await calculatePairedDocs(operationPairs, pairContext)
-  const [operationChanges, tags] = await comparePairedDocs(operationsMap, pairedDocs, apiBuilder, pairContext)
+  const [operationChanges, uniqueDiffsForDocPairs, tags] = await comparePairedDocs(operationsMap, pairedDocs, apiBuilder, pairContext)
   // Duplicates could happen in rare case when document for added/deleted operation was mapped to several documents in other version
   const uniqueOperationChanges = removeObjectDuplicates(
     operationChanges,
     (item) => `${item.apiType}:${item.operationId ?? ''}:${item.previousOperationId ?? ''}`,
   )
 
-  const uniqueDiffs = removeObjectDuplicates(uniqueOperationChanges.flatMap(({ diffs }) => diffs), calculateDiffId)
+  // We only need to additionally deduplicate diffs if there are multiple document pairs
+  // because diffs coming from the same apiDiff call are already deduplicated in comparePairedDocs
+  // This is performance optimization for common case when there is only one document pair
+  const uniqueDiffs = uniqueDiffsForDocPairs.length === 1 ? Array.from(uniqueDiffsForDocPairs[0]) 
+    : removeObjectDuplicates(uniqueDiffsForDocPairs.flatMap(set => Array.from(set)), calculateDiffId)
   const changesSummary = calculateChangeSummary(uniqueDiffs)
   const numberOfImpactedOperations = calculateTotalImpactedSummary(
     uniqueOperationChanges.map(({ impactedSummary }) => impactedSummary),

src/components/compare/compare.utils.ts

@@ -234,8 +234,9 @@ export const comparePairedDocs = async (
   pairedDocs: [ResolvedVersionDocument | undefined, ResolvedVersionDocument | undefined][],
   apiBuilder: ApiBuilder,
   ctx: CompareOperationsPairContext,
-): Promise<[OperationChanges[], string[]]> => {
+): Promise<[OperationChanges[], Set<Diff>[], string[]]> => {
   const operationChanges: OperationChanges[] = []
+  const uniqueDiffsForDocPairs: Set<Diff>[] = []
   const tags = new Set<string>()
 
   for (const [prevDoc, currDoc] of pairedDocs) {
@@ -244,11 +245,14 @@ export const comparePairedDocs = async (
       tags: docsPairTags,
     } = await apiBuilder.compareDocuments!(operationsMap, prevDoc, currDoc, ctx)
 
+    // We can remove duplicates for diffs coming from the same apiDiff call using simple identity
+    uniqueDiffsForDocPairs.push(new Set(docsPairOperationChanges.flatMap(({ diffs }) => diffs ?? [])))
+
     operationChanges.push(...docsPairOperationChanges)
     docsPairTags.forEach(tag => tags.add(tag))
   }
 
-  return [operationChanges, Array.from(tags).sort()]
+  return [operationChanges, uniqueDiffsForDocPairs, Array.from(tags).sort()]
 }
 
 export function createOperationChange(