Fix bug #58400 - incorrect implementation of LocalPath for file URLs (#5779)

4 files changed, 85 insertions, 20 deletions

diff --git a/mcs/class/System/Test/System/UriTest.cs b/mcs/class/System/Test/System/UriTest.cs
index 2db2fb21283..2cabd42af7b 100644
--- a/mcs/class/System/Test/System/UriTest.cs
+++ b/mcs/class/System/Test/System/UriTest.cs
@@ -502,20 +502,14 @@ namespace MonoTests.System
 
 			uri = new Uri ("file:////////cygwin/tmp/hello.txt");
 			Assert.AreEqual ("file://cygwin/tmp/hello.txt", uri.ToString (), "#3a");
-			if (isWin32)
-				Assert.AreEqual ("\\\\cygwin\\tmp\\hello.txt", uri.LocalPath, "#3b win32");
-			else
-				Assert.AreEqual ("/tmp/hello.txt", uri.LocalPath, "#3b *nix");
+			Assert.AreEqual ("\\\\cygwin\\tmp\\hello.txt", uri.LocalPath, "#3b win32");
 			Assert.AreEqual ("file", uri.Scheme, "#3c");
 			Assert.AreEqual ("cygwin", uri.Host, "#3d");
 			Assert.AreEqual ("/tmp/hello.txt", uri.AbsolutePath, "#3e");
 
 			uri = new Uri ("file://mymachine/cygwin/tmp/hello.txt");
 			Assert.AreEqual ("file://mymachine/cygwin/tmp/hello.txt", uri.ToString (), "#4a");
-			if (isWin32)
-				Assert.AreEqual ("\\\\mymachine\\cygwin\\tmp\\hello.txt", uri.LocalPath, "#4b win32");
-			else
-				Assert.AreEqual ("/cygwin/tmp/hello.txt", uri.LocalPath, "#4b *nix");
+			Assert.AreEqual ("\\\\mymachine\\cygwin\\tmp\\hello.txt", uri.LocalPath, "#4b win32");
 			Assert.AreEqual ("file", uri.Scheme, "#4c");
 			Assert.AreEqual ("mymachine", uri.Host, "#4d");
 			Assert.AreEqual ("/cygwin/tmp/hello.txt", uri.AbsolutePath, "#4e");
@@ -537,10 +531,7 @@ namespace MonoTests.System
 			Assert.AreEqual ("/", uri.AbsolutePath, "#6e");
 			Assert.AreEqual ("/", uri.PathAndQuery, "#6f");
 			Assert.AreEqual ("file://one_file.txt/", uri.GetLeftPart (UriPartial.Path), "#6g");
-			if (isWin32)
-				Assert.AreEqual ("\\\\one_file.txt", uri.LocalPath, "#6b");
-			else
-				Assert.AreEqual ("/", uri.LocalPath, "#6b");
+			Assert.AreEqual ("\\\\one_file.txt", uri.LocalPath, "#6b");
 			Assert.AreEqual ("file", uri.Scheme, "#6c");
 			Assert.AreEqual ("one_file.txt", uri.Host, "#6d");
 
@@ -551,10 +542,7 @@ namespace MonoTests.System
 			Assert.AreEqual ("/", uri.AbsolutePath, "#7e");
 			Assert.AreEqual ("/", uri.PathAndQuery, "#7f");
 			Assert.AreEqual ("file://one_file.txt/", uri.GetLeftPart (UriPartial.Path), "#7g");
-			if (isWin32)
-				Assert.AreEqual ("\\\\one_file.txt\\", uri.LocalPath, "#7b");
-			else
-				Assert.AreEqual ("/", uri.LocalPath, "#7b");
+			Assert.AreEqual ("\\\\one_file.txt\\", uri.LocalPath, "#7b");
 			Assert.AreEqual ("file", uri.Scheme, "#7c");
 			Assert.AreEqual ("one_file.txt", uri.Host, "#7d");
 		}
diff --git a/mcs/class/System/Test/System/UriTest2.cs b/mcs/class/System/Test/System/UriTest2.cs
index cbec7b2fc52..85eb8c712cf 100644
--- a/mcs/class/System/Test/System/UriTest2.cs
+++ b/mcs/class/System/Test/System/UriTest2.cs
@@ -875,7 +875,7 @@ TextWriter sw = Console.Out;
 			if (IriParsing)	{
 				Assert.AreEqual ("/dir/subdir/file", uri.AbsolutePath, "AbsolutePath");
 				Assert.AreEqual ("file://host/dir/subdir/file?this-is-not-a-query#but-this-is-a-fragment", uri.AbsoluteUri, "AbsoluteUri");
-				Assert.AreEqual (isWin32 ? "\\\\host\\dir\\subdir\\file" : "/dir/subdir/file", uri.LocalPath, "LocalPath");
+				Assert.AreEqual ("\\\\host\\dir\\subdir\\file", uri.LocalPath, "LocalPath");
 				Assert.AreEqual ("/dir/subdir/file?this-is-not-a-query", uri.PathAndQuery, "PathAndQuery");
 				Assert.AreEqual ("?this-is-not-a-query", uri.Query, "Query");
 				Assert.AreEqual ("file", uri.Segments [3], "Segments [3]");
diff --git a/mcs/class/System/Test/System/UriTest3.cs b/mcs/class/System/Test/System/UriTest3.cs
index a39ac73d0af..f83ec1c62d1 100644
--- a/mcs/class/System/Test/System/UriTest3.cs
+++ b/mcs/class/System/Test/System/UriTest3.cs
@@ -696,6 +696,38 @@ namespace MonoTests.System
 			type = Uri.CheckHostName ("3.141592653589793238462643383279502884197169399375105820974944592._om");
 			Assert.AreEqual (UriHostNameType.Unknown, type, "DomainLabelLength#3");
 		}
+
+        // https://bugzilla.xamarin.com/show_bug.cgi?id=58400
+        [Test]
+        public static void Test_LocalPath_Bug58400()
+        {
+            var uriAndExpected = new [] 
+            {
+                ("file://host/directory/filename", @"\\host\directory\filename"),
+                ("file://host/directory/", @"\\host\directory\"),
+                ("file://host/filename", @"\\host\filename"),
+                ("file://host/", @"\\host\"),
+                ("file://host", @"\\host"),
+                ("file:///directory/filename", "/directory/filename"),
+                ("file:///directory/", "/directory/"),
+                ("file:///filename", "/filename"),
+                ("file:///", "/"),
+                // This is an invalid URI, technically
+                ("file://", "/"),
+	            ("file://////hello/world", @"\\hello\world"),
+            	("file://hello/////world", @"\\hello\\\\\world"),
+            };
+
+            foreach (var tup in uriAndExpected) 
+            {
+                var originalUri = tup.Item1;
+                var expectedLocalPath = tup.Item2;
+                var uri = new Uri (originalUri);
+                var localPath = uri.LocalPath;
+
+                Assert.AreEqual (expectedLocalPath, localPath, originalUri);
+            }
+        }
 	}
 }
 
diff --git a/mcs/class/referencesource/System/net/System/URI.cs b/mcs/class/referencesource/System/net/System/URI.cs
index 24ddbc66e15..8a740ce08b8 100644
--- a/mcs/class/referencesource/System/net/System/URI.cs
+++ b/mcs/class/referencesource/System/net/System/URI.cs
@@ -1070,11 +1070,50 @@ namespace System {
             EnsureParseRemaining();
 
 #if MONO
+            // https://bugzilla.xamarin.com/show_bug.cgi?id=58400
+            bool isFileUrlWithHost =
+                (m_Info.Offset.Host != m_Info.Offset.Path) && 
+                // only file URLs
+                IsFile && 
+                // Paths that got reinterpreted as files would be treated
+                //  as if they have a host, like "/a/b" which maps to "file:///a/b/",
+                //  or "C:\a\b\" which maps to "file:///c:/a/b"
+                OriginalString.StartsWith("file://", StringComparison.Ordinal) &&
+                // file://localhost/x/y needs to produce /x/y
+                !IsLoopback;
+
+            // Manually check for "hosts" that are just forward slashes.
+            if (isFileUrlWithHost) {
+                isFileUrlWithHost = false;
+
+                for (int i = m_Info.Offset.Host; i < m_Info.Offset.Path; i++) {
+                    if (OriginalString[i] != '/') {
+                        isFileUrlWithHost = true;
+                        break;
+                    }
+                }
+            }
+
+            // We need to force generation of a UNC-style path instead of a unix one,
+            // despite the path not being UNC originally
+            bool treatAsUncPath = IsUncPath || isFileUrlWithHost;
+
             //
             // I think this is wrong but it keeps LocalPath fully backward compatible
             //
-            if (IsUncOrDosPath && (IsWindowsFileSystem || !IsUncPath))
+            if (
+                (IsUncOrDosPath && 
+                    (
+                        IsWindowsFileSystem || 
+                        !IsUncPath
+                    )
+                ) ||
+                // If a path has a host name force it into this branch so the UNC code runs
+                isFileUrlWithHost
+            )
 #else
+            bool treatAsUncPath = IsUncPath;
+
             //Other cases will get a Unix-style path
             if (IsUncOrDosPath)
 #endif
@@ -1083,7 +1122,13 @@ namespace System {
                 int start;
 
                 // Do we have a valid local path right in m_string?
-                if (NotAny(Flags.HostNotCanonical|Flags.PathNotCanonical|Flags.ShouldBeCompressed)) {
+                if (
+                    NotAny(Flags.HostNotCanonical|Flags.PathNotCanonical|Flags.ShouldBeCompressed)
+#if MONO
+                    // This branch drops the host name so we can't use it
+                    && !isFileUrlWithHost
+#endif
+                ) {
 
                     start = IsUncPath? m_Info.Offset.Host-2 :m_Info.Offset.Path;
 
@@ -1121,7 +1166,7 @@ namespace System {
                 string host = m_Info.Host;
                 result = new char [host.Length + 3 + m_Info.Offset.Fragment - m_Info.Offset.Path ];
 
-                if (IsUncPath)
+                if (treatAsUncPath)
                 {
                     result[0] = '\\';
                     result[1] = '\\';