Preserve empty CSV fields and quoted-empty rows at EOF

SwiftCSV/Parser.swift

@@ -114,12 +114,9 @@ enum Parser {
         }
 
         // Append remainder of the cache, unless we're past the limit already.
-        if !limitReached(rowIndex) {
-            if !field.isEmpty {
+        if !limitReached(rowIndex), rowIndex >= offset {
+            if !field.isEmpty || !fields.isEmpty || !state.atStart {
                 fields.append(field)
-            }
-
-            if !fields.isEmpty {
                 try rowCallback(fields)
             }
         }

SwiftCSVTests/FinalEmptyFieldTests.swift

@@ -0,0 +1,37 @@
+import XCTest
+@testable import SwiftCSV
+
+class FinalEmptyFieldTests: XCTestCase {
+    func testTrailingEmptyFieldIsPreservedWithoutNewline() throws {
+        for suffix in [",", ",\"\"", ",,"] {
+            let withoutNewline = try Parser.array(text: "value" + suffix, delimiter: .comma)
+            let withNewline = try Parser.array(text: "value" + suffix + "\n", delimiter: .comma)
+            XCTAssertEqual(withoutNewline, withNewline)
+        }
+    }
+
+    func testQuotedEmptySingleFieldIsPreserved() throws {
+        XCTAssertEqual(try Parser.array(text: "\"\"", delimiter: .comma), [[""]])
+        let csv = try EnumeratedCSV(string: "header\n\"\"", delimiter: .comma)
+        XCTAssertEqual(csv.rows, [[""]])
+    }
+
+    func testHeaderAndRowKeepTrailingEmptyColumns() throws {
+        let csv = try EnumeratedCSV(string: "name,\nAlice,", delimiter: .comma)
+        XCTAssertEqual(csv.header, ["name", ""])
+        XCTAssertEqual(csv.rows, [["Alice", ""]])
+        XCTAssertEqual(csv.serialized, "name,\nAlice,")
+    }
+
+    func testEmptyAndCompletedInputDoNotGainRows() throws {
+        XCTAssertEqual(try Parser.array(text: "", delimiter: .comma), [])
+        XCTAssertEqual(try Parser.array(text: " \t", delimiter: .comma), [])
+        XCTAssertEqual(try Parser.array(text: "value\n", delimiter: .comma), [["value"]])
+    }
+
+    func testOffsetsAndLimitsStillExcludeRows() throws {
+        XCTAssertEqual(try Parser.array(text: "value", delimiter: .comma, startAt: 1), [])
+        XCTAssertEqual(try Parser.array(text: "\"\"", delimiter: .comma, rowLimit: 0), [])
+        XCTAssertEqual(try Parser.array(text: "a\n\"\"", delimiter: .comma, rowLimit: 1), [["a"]])
+    }
+}