Parser for actual MSBuild Property option syntax (dotnet#27086)

Adds a parser that can handle all the msbuild property variations, so that arguments that contain a semicolon-
delimited key/value list are correctly escaped.

src/Cli/Microsoft.DotNet.Cli.Utils/MSBuildPropertyParser.cs

@@ -0,0 +1,93 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Text;
+
+#nullable enable
+
+namespace Microsoft.DotNet.Cli.Utils;
+
+public static class MSBuildPropertyParser {
+    public static IEnumerable<(string key, string value)> ParseProperties(string input) {
+        var currentPos = 0;
+        StringBuilder currentKey = new StringBuilder();
+        StringBuilder currentValue = new StringBuilder();
+
+        (string key, string value) EmitAndReset() {
+            var key = currentKey.ToString();
+            var value= currentValue.ToString();
+            currentKey.Clear();
+            currentValue.Clear();
+            return (key, value);
+        }
+
+        char? Peek() => currentPos < input.Length ? input[currentPos] : null;
+
+        bool TryConsume(out char? consumed) {
+            if(input.Length > currentPos) {
+                consumed = input[currentPos];
+                currentPos++;
+                return true;
+            } else {
+                consumed = null;
+                return false;
+            }
+        }
+
+        void ParseKey() {
+            while (TryConsume(out var c) && c != '=') {
+                currentKey.Append(c);
+            }
+        }
+
+        void ParseQuotedValue() {
+            TryConsume(out var leadingQuote); // consume the leading quote, which we know is there
+            currentValue.Append(leadingQuote);
+            while(TryConsume(out char? c)) {
+                currentValue.Append(c);
+                if (c == '"') {
+                    // we're done
+                    return;
+                }
+                if (c == '\\' && Peek() == '"')
+                {
+                    // consume the escaped quote
+                    TryConsume(out var c2); 
+                    currentValue.Append(c2);
+                }
+            }
+        }
+
+        void ParseUnquotedValue() {
+            while(TryConsume(out char? c) && c != ';') {
+                currentValue.Append(c);
+            }
+        }
+
+        void ParseValue() {
+            if (Peek() == '"') {
+                ParseQuotedValue();
+            } else {
+                ParseUnquotedValue();
+            }
+        }
+
+        (string key, string value) ParseKeyValue() {
+            ParseKey();
+            ParseValue();
+            return EmitAndReset();
+        }
+
+        bool AtEnd() => currentPos == input.Length;
+
+        while (!(AtEnd())) {
+            yield return ParseKeyValue();
+            if (Peek() is char c && (c == ';' || c== ',')) {
+                TryConsume(out _); // swallow the next semicolon or comma delimiter
+            }
+        }
+    }
+}

src/Cli/dotnet/OptionForwardingExtensions.cs

@@ -21,8 +21,9 @@ public static class OptionForwardingExtensions
         public static ForwardedOption<string[]> ForwardAsProperty(this ForwardedOption<string[]> option) => option
             .SetForwardingFunction((optionVals) =>
                 optionVals
-                    .Select(optionVal => optionVal.Replace(";", "%3B")) // must escape semicolon-delimited property values when forwarding them to MSBuild
-                    .Select(optionVal => $"{option.Aliases.FirstOrDefault()}:{optionVal}")
+                    .SelectMany(Microsoft.DotNet.Cli.Utils.MSBuildPropertyParser.ParseProperties)
+                    // must escape semicolon-delimited property values when forwarding them to MSBuild
+                    .Select(keyValue => $"{option.Aliases.FirstOrDefault()}:{keyValue.key}={keyValue.value.Replace(";", "%3B")}")
                 );
 
         public static Option<T> ForwardAsMany<T>(this ForwardedOption<T> option, Func<T, IEnumerable<string>> format) => option.SetForwardingFunction(format);

src/Tests/dotnet.Tests/ParserTests/MSBuildArgumentCommandLineParserTests.cs

@@ -49,6 +49,9 @@ public void MSBuildArgumentsAreForwardedCorrectly(string[] arguments, bool build
         [InlineData(new string[] { "-p:teamcity_buildConfName=\"Build, Test and Publish\"" }, new string[] { "--property:teamcity_buildConfName=\"Build, Test and Publish\"" })]
         [InlineData(new string[] { "-p:prop1=true", "-p:prop2=false" }, new string[] { "--property:prop1=true", "--property:prop2=false" })]
         [InlineData(new string[] { "-p:prop1=\".;/opt/usr\"" }, new string[] { "--property:prop1=\".%3B/opt/usr\"" })]
+        [InlineData(new string[] { "-p:prop1=true;prop2=false;prop3=\"wut\";prop4=\"1;2;3\"" }, new string[]{ "--property:prop1=true", "--property:prop2=false", "--property:prop3=\"wut\"", "--property:prop4=\"1%3B2%3B3\""})]
+        [InlineData(new string[] { "-p:prop4=\"1;2;3\"" }, new string[]{ "--property:prop4=\"1%3B2%3B3\""})]
+        [InlineData(new string[] { "-p:prop4=\"1 ;2 ;3 \"" }, new string[]{ "--property:prop4=\"1 %3B2 %3B3 \""})]
         public void Can_pass_msbuild_properties_safely(string[] tokens, string[] forwardedTokens) {
             var forwardingFunction = (CommonOptions.PropertiesOption as ForwardedOption<string[]>).GetForwardingFunction();
             var result = CommonOptions.PropertiesOption.Parse(tokens);