fix: reject reports without headers

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: asizikov

src/pipeline/runPipeline.test.ts

@@ -71,6 +71,14 @@ class CaptureAggregator implements Aggregator<TokenUsageRecord, TokenUsageRecord
 }
 
 describe('runPipeline', () => {
+  it('rejects reports without a header row', async () => {
+    const aggregator = new CaptureAggregator()
+    const file = new File(['\n\n'], 'usage.csv', { type: 'text/csv' })
+
+    await expect(runPipeline(file, [aggregator])).rejects.toThrow(InvalidReportError)
+    expect(aggregator.result()).toEqual([])
+  })
+
   it('returns transition-period metadata for a valid header-only report', async () => {
     const aggregator = new CaptureAggregator()
 

src/pipeline/runPipeline.ts

@@ -1,14 +1,14 @@
 import type { Aggregator } from './aggregators/base'
 import { createAicIncludedCreditsAllocator, type AicIncludedCreditsOverrides } from './aicIncludedCredits'
 import {
+  InvalidReportError,
   parseTokenUsageHeader,
   parseNormalizedTokenUsageRecord,
   parseTokenUsageRecord,
   type TokenUsageHeader,
   type TokenUsageRecord,
 } from './parser'
 import {
-  getDefaultSupportedUsageReportAdapter,
   validateUsageReportFirstRecord,
   validateUsageReportHeader,
   type ReportFormatMetadata,
@@ -35,7 +35,11 @@ async function validateFileFormat(file: File): Promise<ReportFormatMetadata> {
     return validateUsageReportFirstRecord(header, parseTokenUsageRecord(trimmed, header)).metadata
   }
 
-  return (selectedAdapter ?? getDefaultSupportedUsageReportAdapter()).metadata
+  if (!selectedAdapter) {
+    throw new InvalidReportError()
+  }
+
+  return selectedAdapter.metadata
 }
 
 export interface PipelineProgress {