From 436f155963bbf8f1b44bb7ad51119b6d44914a21 Mon Sep 17 00:00:00 2001
From: Miha Zupan <mihazupan.zupan1@gmail.com>
Date: Wed, 26 Aug 2020 15:08:29 +0200
Subject: [PATCH] Reset all Uri fields when reusing an instance (#41324)

* Reset all Uri fields when reusing an instance

* Test combined Uri's AbsoluteUri
---
 .../System.Private.Uri/src/System/Uri.cs      |  2 ++
 .../System.Private.Uri/src/System/UriExt.cs   |  2 ++
 .../tests/FunctionalTests/UriTests.cs         | 19 +++++++++++++++++++
 3 files changed, 23 insertions(+)

diff --git a/src/libraries/System.Private.Uri/src/System/Uri.cs b/src/libraries/System.Private.Uri/src/System/Uri.cs
index 1ed13695b645d..754ac60bf5b87 100644
--- a/src/libraries/System.Private.Uri/src/System/Uri.cs
+++ b/src/libraries/System.Private.Uri/src/System/Uri.cs
@@ -504,6 +504,7 @@ private void CreateUri(Uri baseUri, string? relativeUri, bool dontEscape)
             _flags = Flags.Zero;
             _info = null!;
             _syntax = null!;
+            _originalUnicodeString = null!;
             // If not resolved, we reparse modified Uri string and populate Uri internal data.
             CreateThis(relativeUri, dontEscape, UriKind.Absolute);
         }
@@ -550,6 +551,7 @@ public Uri(Uri baseUri, Uri relativeUri)
             _flags = Flags.Zero;
             _info = null!;
             _syntax = null!;
+            _originalUnicodeString = null!;
             CreateThis(newUriString, dontEscape, UriKind.Absolute);
             DebugSetLeftCtor();
         }
diff --git a/src/libraries/System.Private.Uri/src/System/UriExt.cs b/src/libraries/System.Private.Uri/src/System/UriExt.cs
index 3b4504ac72b26..ff74af22a9bd9 100644
--- a/src/libraries/System.Private.Uri/src/System/UriExt.cs
+++ b/src/libraries/System.Private.Uri/src/System/UriExt.cs
@@ -26,6 +26,8 @@ private void CreateThis(string? uri, bool dontEscape, UriKind uriKind)
 
             _string = uri ?? string.Empty;
 
+            Debug.Assert(_originalUnicodeString is null && _info is null && _syntax is null && _flags == Flags.Zero);
+
             if (dontEscape)
                 _flags |= Flags.UserEscaped;
 
diff --git a/src/libraries/System.Private.Uri/tests/FunctionalTests/UriTests.cs b/src/libraries/System.Private.Uri/tests/FunctionalTests/UriTests.cs
index 5dea3b30e95e9..2b2222f315d82 100644
--- a/src/libraries/System.Private.Uri/tests/FunctionalTests/UriTests.cs
+++ b/src/libraries/System.Private.Uri/tests/FunctionalTests/UriTests.cs
@@ -709,6 +709,25 @@ public static void Uri_EmptyPort_UsesDefaultPort()
             Assert.Equal(80, u.Port);
         }
 
+        [Fact]
+        public static void Uri_CombineUsesNewUriString()
+        {
+            // Tests that internal Uri fields were properly reset during a Combine operation
+            // Otherwise, the wrong Uri string would be used if the relative Uri contains non-ascii characters
+            // This will only affect parsers without the IriParsing flag - only custom parsers
+            UriParser.Register(new GenericUriParser(GenericUriParserOptions.GenericAuthority), "combine-scheme", -1);
+
+            const string BaseUriString = "combine-scheme://foo";
+            const string RelativeUriString = "/relative/uri/with/non/ascii/\u00FC";
+            const string Combined = BaseUriString + "/relative/uri/with/non/ascii/%C3%BC";
+
+            var baseUri = new Uri(BaseUriString, UriKind.Absolute);
+            var relativeUri = new Uri(RelativeUriString, UriKind.Relative);
+
+            Assert.Equal(Combined, new Uri(baseUri, relativeUri).AbsoluteUri);
+            Assert.Equal(Combined, new Uri(baseUri, RelativeUriString).AbsoluteUri);
+        }
+
         [Fact]
         public static void Uri_CachesIdnHost()
         {