Added CsvDataWriterOptions.QuoteNonEmptyStrings (#245)

* Added CsvDataWriterOptions.QuoteNonEmptyStrings to force quoting of strings

* Introduced CsvStringQuoting enum for CsvDataWriterOptions.QuoteStrings

Deprecated CsvDataWriterOptions.QuoteEmptyStrings

source/Sylvan.Data.Csv.Tests/CsvDataWriterTests.cs

@@ -471,12 +471,18 @@ public void CsvWriteBatches()
 	}
 
 	[Theory]
-	[InlineData(true, "Name\n\"\"\n\n")]
-	[InlineData(false, "Name\n\n\n")]
-	public void QuoteEmptyStrings(bool mode, string result)
+	[InlineData(CsvStringQuoting.Default, "Name\n1\n\n\n")]
+	[InlineData(CsvStringQuoting.AlwaysQuoteEmpty, "Name\n1\n\"\"\n\n")]
+	[InlineData(CsvStringQuoting.AlwaysQuoteNonEmpty, "\"Name\"\n\"1\"\n\n\n")]
+	[InlineData(CsvStringQuoting.AlwaysQuote, "\"Name\"\n\"1\"\n\"\"\n\n")]
+	public void QuoteStringsOptions(CsvStringQuoting mode, string result)
 	{
 		var data = new[]
 			{
+				new
+				{
+					Name = "1"
+				},
 				new
 				{
 					Name = ""
@@ -487,7 +493,7 @@ public void QuoteEmptyStrings(bool mode, string result)
 				},
 			};
 		var reader = data.AsDataReader();
-		var opts = new CsvDataWriterOptions { QuoteEmptyStrings = mode, NewLine = "\n" };
+		var opts = new CsvDataWriterOptions { QuoteStrings = mode, NewLine = "\n" };
 		var sw = new StringWriter();
 		var writer = CsvDataWriter.Create(sw, opts);
 		writer.Write(reader);

source/Sylvan.Data.Csv/CsvDataWriter.cs

@@ -447,7 +447,7 @@ bool IsFastTimeOnly
 	readonly CsvWriter csvWriter;
 
 	readonly bool writeHeaders;
-	readonly bool quoteEmptyStrings;
+	readonly CsvStringQuoting quoteStrings;
 	readonly char delimiter;
 	readonly char quote;
 	readonly char escape;
@@ -530,7 +530,7 @@ public static CsvDataWriter Create(TextWriter writer, char[] buffer, CsvDataWrit
 		this.dateOnlyFormat = options.DateOnlyFormat;
 #endif
 		this.writeHeaders = options.WriteHeaders;
-		this.quoteEmptyStrings = options.QuoteEmptyStrings;
+		this.quoteStrings = options.QuoteStrings;
 		this.delimiter = options.Delimiter;
 		this.quote = options.Quote;
 		this.escape = options.Escape;

source/Sylvan.Data.Csv/CsvDataWriterOptions.cs

@@ -3,6 +3,33 @@
 
 namespace Sylvan.Data.Csv;
 
+/// <summary>
+/// Specifies how strings are quoted
+/// </summary>
+[Flags]
+public enum CsvStringQuoting
+{
+	/// <summary>
+	/// Strings are only quoted when it is required.
+	/// </summary>
+	Default = 0,
+
+	/// <summary>
+	/// Empty strings are always quoted. This distinguishes them from null.
+	/// </summary>
+	AlwaysQuoteEmpty = 1,
+
+	/// <summary>
+	/// Non-empty strings are always quoted. This helps prevent confusion with numbers and dates.
+	/// </summary>
+	AlwaysQuoteNonEmpty = 2,
+
+	/// <summary>
+	/// All strings are always quoted.
+	/// </summary>
+	AlwaysQuote = 3,
+}
+
 /// <summary>
 /// Options for configuring a CsvWriter.
 /// </summary>
@@ -30,6 +57,7 @@ public CsvDataWriterOptions()
 		this.BinaryEncoding = BinaryEncoding.Base64;
 		this.Style = CsvStyle.Standard;
 		this.Delimiter = DefaultDelimiter;
+		this.QuoteStrings = CsvStringQuoting.Default;
 		this.Quote = DefaultQuote;
 		this.Escape = DefaultEscape;
 		this.Comment = DefaultComment;
@@ -121,10 +149,26 @@ public string? TimeFormat {
 	public char Delimiter { get; set; }
 
 	/// <summary>
-	/// Empty strings will be written as empty quotes in the CSV. 
+	/// The rules to use when quoting strings, defaults to <see cref="CsvStringQuoting.Default"/>
+	/// </summary>
+	public CsvStringQuoting QuoteStrings { get; set; }
+
+	/// <summary>
+	/// Empty strings will be written as empty quotes in the CSV.
 	/// This allows distinguishing empty strings from null.
 	/// </summary>
-	public bool QuoteEmptyStrings { get; set; }
+	[Obsolete("Use QuoteStrings instead.")]
+	public bool QuoteEmptyStrings
+	{
+		get => QuoteStrings.HasFlag(CsvStringQuoting.AlwaysQuoteEmpty);
+		set
+		{
+			if (value)
+				QuoteStrings |= CsvStringQuoting.AlwaysQuoteEmpty;
+			else
+				QuoteStrings &= ~CsvStringQuoting.AlwaysQuoteEmpty;
+		}
+	}
 
 	/// <summary>
 	/// The character to use for quoting fields. The default is '"'.
@@ -184,7 +228,7 @@ internal void Validate()
 			Quote >= 128 ||
 			Escape >= 128 ||
 			Comment >= 128 ||
-			(QuoteEmptyStrings && Style == CsvStyle.Escaped)
+			(QuoteStrings != CsvStringQuoting.Default && Style == CsvStyle.Escaped)
 			;
 		if (invalid)
 			throw new CsvConfigurationException();

source/Sylvan.Data.Csv/CsvWriter.cs

@@ -114,10 +114,15 @@ static int WriteValueOptimistic(WriterContext context, string value, char[] buff
 		{
 			var pos = offset;
 			var needsEscape = context.writer.needsEscape;
-			if (value.Length == 0 && context.writer.quoteEmptyStrings)
+			if (value.Length == 0)
 			{
-				return NeedsQuoting;
+				if (context.writer.quoteStrings.HasFlag(CsvStringQuoting.AlwaysQuoteEmpty))
+					return NeedsQuoting;
+				else
+					return 0;
 			}
+			else if (context.writer.quoteStrings.HasFlag(CsvStringQuoting.AlwaysQuoteNonEmpty))
+				return NeedsQuoting;
 
 			if (pos + value.Length >= buffer.Length)
 				return InsufficientSpace;