fix(inspector): make the CSV doubled-quote escape track the selected quote character

Author: datlechin

Plugins/TableProPluginKit/CSVDialect.swift

@@ -17,7 +17,7 @@ public struct CSVDialect: Equatable, Sendable {
 
     public var delimiter: UInt8
     public var quoteChar: UInt8
-    public var escapeChar: UInt8 = 0x22
+    public var escapeChar: UInt8
     public var encoding: String.Encoding
     public var lineEnding: LineEnding
     public var hasBom: Bool
@@ -31,6 +31,7 @@ public struct CSVDialect: Equatable, Sendable {
     ) {
         self.delimiter = delimiter
         self.quoteChar = quoteChar
+        self.escapeChar = quoteChar
         self.encoding = encoding
         self.lineEnding = lineEnding
         self.hasBom = hasBom

TablePro/Views/Inspector/CSVPropertyOptions.swift

@@ -26,6 +26,8 @@ enum CSVPropertyOptions {
         (String(localized: "Backslash  \\"), 0x5C),
     ]
 
+    static let backslashEscapeIndex = 1
+
     static let encodings: [(label: String, encoding: String.Encoding)] = [
         ("UTF-8", .utf8),
         ("UTF-16 LE", .utf16LittleEndian),
@@ -49,7 +51,7 @@ enum CSVPropertyOptions {
     }
 
     static func escapeIndex(for byte: UInt8) -> Int {
-        escapes.firstIndex { $0.byte == byte } ?? 0
+        byte == escapes[backslashEscapeIndex].byte ? backslashEscapeIndex : 0
     }
 
     static func encodingIndex(for encoding: String.Encoding) -> Int {
@@ -75,7 +77,9 @@ enum CSVPropertyOptions {
             lineEnding: lineEndings.indices.contains(lineEndingIndex) ? lineEndings[lineEndingIndex].value : base.lineEnding,
             hasBom: base.hasBom
         )
-        dialect.escapeChar = escapes.indices.contains(escapeIndex) ? escapes[escapeIndex].byte : base.escapeChar
+        dialect.escapeChar = escapeIndex == backslashEscapeIndex
+            ? escapes[backslashEscapeIndex].byte
+            : dialect.quoteChar
         return dialect
     }
 }

TableProTests/Plugins/CSVInspectorTests.swift

@@ -84,6 +84,11 @@ struct CSVDialectDetectionTests {
         let detected = CSVDialect.detect(from: "a,b\n1,2\n".data(using: .utf8)!)
         #expect(detected.escapeChar == 0x22)
     }
+
+    @Test("Escape character follows a non-default quote character")
+    func escapeFollowsQuote() {
+        #expect(CSVDialect(delimiter: 0x2C, quoteChar: 0x27).escapeChar == 0x27)
+    }
 }
 
 @Suite("CSVStreamingParser")
@@ -159,6 +164,18 @@ struct CSVStreamingParserTests {
         #expect(fields == [#"a\b"#])
     }
 
+    @Test("field(at:column:) honors the backslash escape inside a quoted field")
+    func fieldBackslashEscape() {
+        var dialect = CSVDialect.csv
+        dialect.escapeChar = 0x5C
+        let (data, ranges, parser) = parse(#""a\"b",c"# + "\n", dialect: dialect)
+        let first = data.withUnsafeBytes { raw -> String in
+            guard let base = raw.bindMemory(to: UInt8.self).baseAddress else { return "" }
+            return parser.field(UnsafeBufferPointer(start: base, count: raw.count), range: ranges[0], column: 0)
+        }
+        #expect(first == #"a"b"#)
+    }
+
     @Test("Empty fields preserved")
     func emptyFields() {
         let (data, ranges, parser) = parse(",,,\n")

TableProTests/Views/CSVPropertyOptionsTests.swift

@@ -40,4 +40,18 @@ struct CSVPropertyOptionsTests {
         #expect(dialect.lineEnding == .cr)
         #expect(dialect.hasBom)
     }
+
+    @Test("The doubled-quote escape follows the selected quote character")
+    func doubledQuoteEscapeTracksQuote() {
+        let dialect = CSVPropertyOptions.dialect(
+            base: CSVDialect(delimiter: 0x2C),
+            delimiterIndex: 0,
+            quoteIndex: CSVPropertyOptions.quoteIndex(for: 0x27),
+            escapeIndex: 0,
+            encodingIndex: 0,
+            lineEndingIndex: 0
+        )
+        #expect(dialect.quoteChar == 0x27)
+        #expect(dialect.escapeChar == 0x27)
+    }
 }