Implement better way to test for in-memory file

src/PowerShellEditorServices/Workspace/Workspace.cs

@@ -390,22 +390,30 @@ internal static bool IsPathInMemory(string filePath)
             // view of the current file or an untitled file.
             try
             {
-                // NotSupportedException or ArgumentException gets thrown when
-                // given an invalid path.  Since any non-standard path will
-                // trigger this, assume that it means it's an in-memory file
-                // unless the path starts with file:
-                Path.GetFullPath(filePath);
+                // File system absoulute paths will have a URI scheme of file:.
+                // Other schemes like "untitled:" and "gitlens-git:" will return false for IsFile.
+                var uri = new Uri(filePath);
+                isInMemory = !uri.IsFile;
             }
-            catch (ArgumentException)
+            catch (UriFormatException)
             {
-                isInMemory = true;
-            }
-            catch (NotSupportedException)
-            {
-                isInMemory = true;
+                // Relative file paths cause a UriFormatException.
+                // In this case, fallback to using Path.GetFullPath().
+                try
+                {
+                    Path.GetFullPath(filePath);
+                }
+                catch (Exception ex) when (ex is ArgumentException || ex is NotSupportedException)
+                {
+                    isInMemory = true;
+                }
+                catch (PathTooLongException)
+                {
+                    // If we ever get here, it should be an actual file so, not in memory
+                }
             }
 
-            return !filePath.ToLower().StartsWith("file:") && isInMemory;
+            return isInMemory;
         }
 
         private string GetBaseFilePath(string filePath)

test/PowerShellEditorServices.Test/Session/WorkspaceTests.cs

@@ -3,12 +3,10 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 //
 
-using Microsoft.PowerShell.EditorServices;
 using System;
 using System.IO;
-using System.Linq;
-using Xunit;
 using Microsoft.PowerShell.EditorServices.Utility;
+using Xunit;
 
 namespace Microsoft.PowerShell.EditorServices.Test.Session
 {
@@ -35,5 +33,41 @@ public void CanResolveWorkspaceRelativePath()
             Assert.Equal(@"..\PeerPath\FilePath.ps1", workspace.GetRelativePath(testPathOutside));
             Assert.Equal(testPathAnotherDrive, workspace.GetRelativePath(testPathAnotherDrive));
         }
+
+        [Fact]
+        public void CanDetermineIsPathInMemory()
+        {
+            var tempDir = Environment.GetEnvironmentVariable("TEMP");
+            var shortDirPath = Path.Combine(tempDir, "GitHub", "PowerShellEditorServices");
+            var shortFilePath = Path.Combine(shortDirPath, "foo.ps1");
+            var shortUriForm = "git:/c%3A/Users/Keith/GitHub/dahlbyk/posh-git/src/PoshGitTypes.ps1?%7B%22path%22%3A%22c%3A%5C%5CUsers%5C%5CKeith%5C%5CGitHub%5C%5Cdahlbyk%5C%5Cposh-git%5C%5Csrc%5C%5CPoshGitTypes.ps1%22%2C%22ref%22%3A%22~%22%7D";
+            var longUriForm = "gitlens-git:c%3A%5CUsers%5CKeith%5CGitHub%5Cdahlbyk%5Cposh-git%5Csrc%5CPoshGitTypes%3Ae0022701.ps1?%7B%22fileName%22%3A%22src%2FPoshGitTypes.ps1%22%2C%22repoPath%22%3A%22c%3A%2FUsers%2FKeith%2FGitHub%2Fdahlbyk%2Fposh-git%22%2C%22sha%22%3A%22e0022701fa12e0bc22d0458673d6443c942b974a%22%7D";
+
+            var testCases = new[] {
+                // Test short file absolute paths
+                new { IsInMemory = false, Path = shortDirPath },
+                new { IsInMemory = false, Path = shortFilePath },
+                new { IsInMemory = false, Path = new Uri(shortDirPath).ToString() },
+                new { IsInMemory = false, Path = new Uri(shortFilePath).ToString() },
+
+                // Test short file relative paths - not sure we'll ever get these but just in case
+                new { IsInMemory = false, Path = "foo.ps1" },
+                new { IsInMemory = false, Path = ".." + Path.DirectorySeparatorChar + "foo.ps1" },
+
+                // Test short non-file paths
+                new { IsInMemory = true,  Path = "untitled:untitled-1" },
+                new { IsInMemory = true,  Path = shortUriForm },
+
+                // Test long non-file path - known to have crashed PSES
+                new { IsInMemory = true,  Path = longUriForm },
+            };
+
+            foreach (var testCase in testCases)
+            {
+                Assert.True(
+                    Workspace.IsPathInMemory(testCase.Path) == testCase.IsInMemory,
+                    $"Testing path {testCase.Path}");
+            }
+        }
     }
 }