Treat bom-only CSV file as empty (#112)

* test: reproduce the problem we faced

Signed-off-by: Kengo TODA <toda_k@henry.jp>

* fix: lines contain only BOM were not handled as empty lines

Signed-off-by: Kengo TODA <toda_k@henry.jp>

* chore: follow suggestions from CodeFactor

Signed-off-by: Kengo TODA <toda_k@henry.jp>

* chore: follow suggestions from CodeFactor

Signed-off-by: Kengo TODA <toda_k@henry.jp>

Signed-off-by: Kengo TODA <toda_k@henry.jp>

Author: KengoTODA

src/commonMain/kotlin/com/github/doyaaaaaken/kotlincsv/client/BufferedLineReader.kt

@@ -6,14 +6,20 @@ package com.github.doyaaaaaken.kotlincsv.client
 internal class BufferedLineReader(
     private val br: Reader
 ) {
+    companion object {
+        private const val BOM = '\uFEFF'
+    }
+
+    private fun StringBuilder.isEmptyLine(): Boolean =
+        this.isEmpty() || this.length == 1 && this[0] == BOM
 
     fun readLineWithTerminator(): String? {
         val sb = StringBuilder()
         do {
             val c = br.read()
 
             if (c == -1) {
-                if (sb.isEmpty()) {
+                if (sb.isEmptyLine()) {
                     return null
                 } else {
                     break

src/jvmTest/kotlin/com/github/doyaaaaaken/kotlincsv/client/CsvReaderTest.kt

@@ -138,6 +138,12 @@ class CsvReaderTest : WordSpec({
             }.readAll(readTestDataFile("bom.csv"))
             result shouldBe listOf(listOf("a", "b", "c"))
         }
+        "read empty csv with BOM" {
+            val result = csvReader {
+                escapeChar = '\\'
+            }.readAll(readTestDataFile("empty-bom.csv"))
+            result shouldBe listOf()
+        }
         //refs https://github.com/tototoshi/scala-csv/issues/22
         "read csv with \u2028 field" {
             val result = csvReader().readAll(readTestDataFile("unicode2028.csv"))

src/jvmTest/resources/testdata/csv/empty-bom.csv

@@ -0,0 +1 @@
+