Two minor path-related changes

- System.IO.Compression.ZipFile was unnecessarily including PathInternals.Windows/Unix.cs

- A System.Runtime test for PathTooLongException was passing but for the wrong reason: on Windows it was testing a path longer than max path, whereas on Unix it happened to be passing because of limitations on directory length in a path.  I've tweaked it to avoid assumptions about max path length.

I found these by scrubbing through all of corefx looking for additional uses of max path.  The only other one now outside of System.IO.FileSystem / System.Runtime.Extensions and the associated interop files is in Semaphore, which limits a semaphore name to be MAX_PATH.  We'll need to address that separately when we determine how best to handle named synchronization primitives on Unix (the limit is unlikely to be the MAX_PATH equivalent on Unix.)

Author: stephentoub

src/System.IO.Compression.ZipFile/src/System.IO.Compression.ZipFile.csproj

@@ -24,19 +24,10 @@
   </ItemGroup>
   <!-- Windows -->
   <ItemGroup Condition="'$(TargetsWindows)' == 'true'">
-    <Compile Include="$(CommonPath)\System\IO\PathInternal.Windows.cs">
-      <Link>Common\System\IO\PathInternal.Windows.cs</Link>
-    </Compile>
     <Compile Include="$(CommonPath)\System\IO\PathInternal.CaseInsensitive.cs">
       <Link>Common\System\IO\PathInternal.CaseInsensitive.cs</Link>
     </Compile>
   </ItemGroup>
-  <!-- Unix -->
-  <ItemGroup Condition="'$(TargetsUnix)' == 'true'">
-    <Compile Include="$(CommonPath)\System\IO\PathInternal.Unix.cs">
-      <Link>Common\System\IO\PathInternal.Unix.cs</Link>
-    </Compile>
-  </ItemGroup>
   <!-- FreeBSD -->
   <ItemGroup Condition="'$(TargetsFreeBSD)' == 'true'">
     <Compile Include="$(CommonPath)\System\IO\PathInternal.CaseSensitive.cs">

src/System.Runtime/tests/System/IO/PathTooLongException.cs

@@ -38,18 +38,20 @@ public static void PathTooLongException_From_Path()
         // This test case ensures that the PathTooLongException defined in System.IO.Primitives is the same that
         // is thrown by Path.  The S.IO.FS.P implementation forwards to the core assembly to ensure this is true.
 
-        string subPath = "subdir\\";
-        const int MAX_PATH = 260;
-
-        // Create a relative path that is longer than maxpath.
-        StringBuilder path = new StringBuilder();
-        while (path.Length <= MAX_PATH)
+        // Build up a path until GetFullPath throws, and verify that the right exception type
+        // emerges from it and related APIs.
+        var sb = new StringBuilder("directoryNameHere" + Path.DirectorySeparatorChar);
+        string path = null;
+        Assert.Throws<PathTooLongException>(new Action(() =>
         {
-            path.Append(subPath);
-        }
-
-        // Not available in N: Assert.Throws<PathTooLongException>(() => Path.GetFullPath(path.ToString()));
-        Assert.Throws<PathTooLongException>(() => Path.GetPathRoot(path.ToString()));
-        Assert.Throws<PathTooLongException>(() => Path.GetDirectoryName(path.ToString()));
+            while (true)
+            {
+                path = sb.ToString();
+                Path.GetPathRoot(path); // will eventually throw when path is too long
+                sb.Append(path); // double the number of directories for the next time
+            }
+        }));
+        Assert.Throws<PathTooLongException>(() => Path.GetFullPath(path));
+        Assert.Throws<PathTooLongException>(() => Path.GetDirectoryName(path));
     }
 }