fix: Restore check for duplicate headers

Author: effigies

src/files/tsv.test.ts

@@ -157,6 +157,18 @@ Deno.test('TSV loading', async (t) => {
     assertEquals(repeatMap.c, ['3', '3'])
   })
 
+  await t.step('Raises issue on duplicate header', async () => {
+    const file = pathToFile('/duplicate_header.tsv')
+    file.stream = streamFromString('a\ta\n1\t2\n')
+
+    try {
+      await loadTSV(file)
+      assert(false, 'Expected error')
+    } catch (e: any) {
+      assertObjectMatch(e, { key: 'TSV_COLUMN_HEADER_DUPLICATE', evidence: 'a, a' })
+    }
+  })
+
   // Tests will have populated the memoization cache
   loadTSV.cache.clear()
 })

src/files/tsv.ts

@@ -18,6 +18,10 @@ async function _loadTSV(file: BIDSFile, maxRows: number = -1): Promise<ColumnsMa
     const headerRow = await reader.read()
     const headers = (headerRow.done || !headerRow.value) ? [] : headerRow.value.split('\t')
 
+    if (new Set(headers).size !== headers.length) {
+      throw { key: 'TSV_COLUMN_HEADER_DUPLICATE', evidence: headers.join(', ') }
+    }
+
     // Initialize columns in array for construction efficiency
     const initialCapacity = maxRows >= 0 ? maxRows : 1000
     const columns: string[][] = headers.map(() => new Array<string>(initialCapacity))