feat: add symbolic link functionality (#965)

vbreuss · web-flow · commit 966b1372e2a6 · 2023-04-11T12:50:44.000Z
Implement the `CreateSymbolicLink` and `ResolveLinkTarget` methods on `Directory`, `DirectoryInfo`, `File` and `FileInfo`.
diff --git a/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockDirectory.cs b/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockDirectory.cs
@@ -530,7 +530,43 @@ public override void Move(string sourceDirName, string destDirName)
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(string linkPath, bool returnFinalTarget)
         {
-            throw CommonExceptions.NotImplemented();
+            var initialContainer = mockFileDataAccessor.GetFile(linkPath);
+            if (initialContainer.LinkTarget != null)
+            {
+                var nextLocation = initialContainer.LinkTarget;
+                var nextContainer = mockFileDataAccessor.GetFile(nextLocation);
+
+                if (returnFinalTarget)
+                {
+                    // The maximum number of symbolic links that are followed:
+                    // https://learn.microsoft.com/en-us/dotnet/api/system.io.directory.resolvelinktarget?view=net-6.0#remarks
+                    int maxResolveLinks = XFS.IsWindowsPlatform() ? 63 : 40;
+                    for (int i = 1; i < maxResolveLinks; i++)
+                    {
+                        if (nextContainer.LinkTarget == null)
+                        {
+                            break;
+                        }
+                        nextLocation = nextContainer.LinkTarget;
+                        nextContainer = mockFileDataAccessor.GetFile(nextLocation);
+                    }
+
+                    if (nextContainer.LinkTarget != null)
+                    {
+                        throw new IOException($"The name of the file cannot be resolved by the system. : '{linkPath}'");
+                    }
+                }
+
+                if (nextContainer.IsDirectory)
+                {
+                    return new MockDirectoryInfo(mockFileDataAccessor, nextLocation);
+                }
+                else
+                {
+                    return new MockFileInfo(mockFileDataAccessor, nextLocation);
+                }
+            }
+            throw new IOException($"The name of the file cannot be resolved by the system. : '{linkPath}'");
         }
     
 #endif
diff --git a/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockDirectoryInfo.cs b/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockDirectoryInfo.cs
@@ -52,7 +52,7 @@ public MockDirectoryInfo(IMockFileDataAccessor mockFileDataAccessor, string dire
         /// <inheritdoc />
         public override void CreateAsSymbolicLink(string pathToTarget)
         {
-            throw CommonExceptions.NotImplemented();
+            FileSystem.Directory.CreateSymbolicLink(FullName, pathToTarget);
         }
 #endif
 
@@ -74,7 +74,7 @@ public override void Refresh()
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)
         {
-            throw CommonExceptions.NotImplemented();
+            return FileSystem.Directory.ResolveLinkTarget(FullName, returnFinalTarget);
         }
 #endif
 
diff --git a/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFile.cs b/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFile.cs
@@ -777,7 +777,43 @@ public override void Replace(string sourceFileName, string destinationFileName,
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(string linkPath, bool returnFinalTarget)
         {
-            throw CommonExceptions.NotImplemented();
+            var initialContainer = mockFileDataAccessor.GetFile(linkPath);
+            if (initialContainer.LinkTarget != null)
+            {
+                var nextLocation = initialContainer.LinkTarget;
+                var nextContainer = mockFileDataAccessor.GetFile(nextLocation);
+
+                if (returnFinalTarget)
+                {
+                    // The maximum number of symbolic links that are followed:
+                    // https://learn.microsoft.com/en-us/dotnet/api/system.io.directory.resolvelinktarget?view=net-6.0#remarks
+                    int maxResolveLinks = XFS.IsWindowsPlatform() ? 63 : 40;
+                    for (int i = 1; i < maxResolveLinks; i++)
+                    {
+                        if (nextContainer.LinkTarget == null)
+                        {
+                            break;
+                        }
+                        nextLocation = nextContainer.LinkTarget;
+                        nextContainer = mockFileDataAccessor.GetFile(nextLocation);
+                    }
+
+                    if (nextContainer.LinkTarget != null)
+                    {
+                        throw new IOException($"The name of the file cannot be resolved by the system. : '{linkPath}'");
+                    }
+                }
+
+                if (nextContainer.IsDirectory)
+                {
+                    return new MockDirectoryInfo(mockFileDataAccessor, nextLocation);
+                }
+                else
+                {
+                    return new MockFileInfo(mockFileDataAccessor, nextLocation);
+                }
+            }
+            throw new IOException($"The name of the file cannot be resolved by the system. : '{linkPath}'");
         }
 #endif
 
diff --git a/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFileInfo.cs b/src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFileInfo.cs
@@ -29,7 +29,7 @@ public MockFileInfo(IMockFileDataAccessor mockFileSystem, string path) : base(mo
         /// <inheritdoc />
         public override void CreateAsSymbolicLink(string pathToTarget)
         {
-            throw CommonExceptions.NotImplemented();
+            FileSystem.File.CreateSymbolicLink(FullName, pathToTarget);
         }
 #endif
 
@@ -51,7 +51,7 @@ public override void Refresh()
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)
         {
-            throw CommonExceptions.NotImplemented();
+            return FileSystem.File.ResolveLinkTarget(FullName, returnFinalTarget);
         }
 #endif
 
diff --git a/src/TestableIO.System.IO.Abstractions.Wrappers/DirectoryInfoWrapper.cs b/src/TestableIO.System.IO.Abstractions.Wrappers/DirectoryInfoWrapper.cs
@@ -22,7 +22,7 @@ public DirectoryInfoWrapper(IFileSystem fileSystem, DirectoryInfo instance) : ba
         /// <inheritdoc />
         public override void CreateAsSymbolicLink(string pathToTarget)
         {
-            throw new NotImplementedException();
+            instance.CreateAsSymbolicLink(pathToTarget);
         }
 #endif
 
@@ -42,7 +42,8 @@ public override void Refresh()
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)
         {
-            throw new NotImplementedException();
+            return instance.ResolveLinkTarget(returnFinalTarget)
+                .WrapFileSystemInfo(FileSystem);
         }
 #endif
 
diff --git a/src/TestableIO.System.IO.Abstractions.Wrappers/DirectoryWrapper.cs b/src/TestableIO.System.IO.Abstractions.Wrappers/DirectoryWrapper.cs
@@ -34,7 +34,8 @@ public override IDirectoryInfo CreateDirectory(string path, UnixFileMode unixCre
         /// <inheritdoc />
         public override IFileSystemInfo CreateSymbolicLink(string path, string pathToTarget)
         {
-            return Directory.CreateSymbolicLink(path, pathToTarget).WrapFileSystemInfo(FileSystem);
+            return Directory.CreateSymbolicLink(path, pathToTarget)
+                .WrapFileSystemInfo(FileSystem);
         }
 #endif
 
@@ -219,7 +220,8 @@ public override void Move(string sourceDirName, string destDirName)
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(string linkPath, bool returnFinalTarget)
         {
-            throw new NotSupportedException("TODO: Missing object implementing `IFileSystemInfo`");
+            return Directory.ResolveLinkTarget(linkPath, returnFinalTarget)
+                .WrapFileSystemInfo(FileSystem);
         }
 #endif
 
diff --git a/src/TestableIO.System.IO.Abstractions.Wrappers/FileInfoWrapper.cs b/src/TestableIO.System.IO.Abstractions.Wrappers/FileInfoWrapper.cs
@@ -39,7 +39,8 @@ public override void Refresh()
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)
         {
-            throw new NotImplementedException();
+            return instance.ResolveLinkTarget(returnFinalTarget)
+                .WrapFileSystemInfo(FileSystem);
         }
 #endif
 
diff --git a/src/TestableIO.System.IO.Abstractions.Wrappers/FileWrapper.cs b/src/TestableIO.System.IO.Abstractions.Wrappers/FileWrapper.cs
@@ -79,7 +79,8 @@ public override FileSystemStream Create(string path, int bufferSize, FileOptions
         /// <inheritdoc />
         public override IFileSystemInfo CreateSymbolicLink(string path, string pathToTarget)
         {
-            return File.CreateSymbolicLink(path, pathToTarget).WrapFileSystemInfo(FileSystem);
+            return File.CreateSymbolicLink(path, pathToTarget)
+                .WrapFileSystemInfo(FileSystem);
         }
 #endif
         /// <inheritdoc />
@@ -347,7 +348,8 @@ public override void Replace(string sourceFileName, string destinationFileName,
         /// <inheritdoc />
         public override IFileSystemInfo ResolveLinkTarget(string linkPath, bool returnFinalTarget)
         {
-            throw new NotImplementedException();
+            return File.ResolveLinkTarget(linkPath, returnFinalTarget)
+                .WrapFileSystemInfo(FileSystem);
         }
 #endif
 
diff --git a/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockDirectoryInfoSymlinkTests.cs b/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockDirectoryInfoSymlinkTests.cs
@@ -0,0 +1,69 @@
+﻿using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Versioning;
+using System.Security.AccessControl;
+using NUnit.Framework;
+
+namespace System.IO.Abstractions.TestingHelpers.Tests
+{
+    using XFS = MockUnixSupport;
+
+    [TestFixture]
+    public class MockDirectoryInfoSymlinkTests
+    {
+
+#if FEATURE_CREATE_SYMBOLIC_LINK
+
+        [Test]
+        public void MockDirectoryInfo_ResolveLinkTarget_ShouldReturnPathOfTargetLink()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+
+            var result = fileSystem.DirectoryInfo.New("foo").ResolveLinkTarget(false);
+
+            Assert.AreEqual("bar", result.Name);
+        }
+
+        [Test]
+        public void MockDirectoryInfo_ResolveLinkTarget_WithFinalTarget_ShouldReturnPathOfTargetLink()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+            fileSystem.Directory.CreateSymbolicLink("foo1", "foo");
+
+            var result = fileSystem.DirectoryInfo.New("foo1").ResolveLinkTarget(true);
+
+            Assert.AreEqual("bar", result.Name);
+        }
+
+        [Test]
+        public void MockDirectoryInfo_ResolveLinkTarget_WithoutFinalTarget_ShouldReturnFirstLink()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+            fileSystem.Directory.CreateSymbolicLink("foo1", "foo");
+
+            var result = fileSystem.DirectoryInfo.New("foo1").ResolveLinkTarget(false);
+
+            Assert.AreEqual("foo", result.Name);
+        }
+
+        [Test]
+        public void MockDirectoryInfo_ResolveLinkTarget_WithoutTargetLink_ShouldThrowIOException()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+
+            Assert.Throws<IOException>(() =>
+            {
+                fileSystem.DirectoryInfo.New("bar").ResolveLinkTarget(false);
+            });
+        }
+#endif
+    }
+}
diff --git a/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockDirectorySymlinkTests.cs b/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockDirectorySymlinkTests.cs
@@ -1,8 +1,4 @@
-﻿using System.Collections.Generic;
-using System.Linq;
-using System.Runtime.Versioning;
-using System.Security.AccessControl;
-using NUnit.Framework;
+﻿using NUnit.Framework;
 
 namespace System.IO.Abstractions.TestingHelpers.Tests
 {
@@ -201,6 +197,85 @@ public void MockDirectory_CreateSymbolicLink_ShouldFailIfTargetDoesNotExist()
             // Assert
             Assert.That(ex.Message.Contains(pathToTarget));
         }
+
+        [Test]
+        public void MockDirectory_ResolveLinkTarget_ShouldReturnPathOfTargetLink()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+
+            var result = fileSystem.Directory.ResolveLinkTarget("foo", false);
+
+            Assert.AreEqual("bar", result.Name);
+        }
+
+        [Test]
+        public void MockDirectory_ResolveLinkTarget_WithFinalTarget_ShouldReturnPathOfTargetLink()
+        {
+            // The maximum number of symbolic links that are followed:
+            // https://learn.microsoft.com/en-us/dotnet/api/system.io.directory.resolvelinktarget?view=net-6.0#remarks
+            var maxResolveLinks = XFS.IsWindowsPlatform() ? 63 : 40;
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            var previousPath = "bar";
+            for (int i = 0; i < maxResolveLinks; i++)
+            {
+                string newPath = $"foo-{i}";
+                fileSystem.Directory.CreateSymbolicLink(newPath, previousPath);
+                previousPath = newPath;
+            }
+
+            var result = fileSystem.Directory.ResolveLinkTarget(previousPath, true);
+
+            Assert.AreEqual("bar", result.Name);
+        }
+
+        [Test]
+        public void MockDirectory_ResolveLinkTarget_WithFinalTargetWithTooManyLinks_ShouldThrowIOException()
+        {
+            // The maximum number of symbolic links that are followed:
+            // https://learn.microsoft.com/en-us/dotnet/api/system.io.directory.resolvelinktarget?view=net-6.0#remarks
+            var maxResolveLinks = XFS.IsWindowsPlatform() ? 63 : 40;
+            maxResolveLinks++;
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            var previousPath = "bar";
+            for (int i = 0; i < maxResolveLinks; i++)
+            {
+                string newPath = $"foo-{i}";
+                fileSystem.Directory.CreateSymbolicLink(newPath, previousPath);
+                previousPath = newPath;
+            }
+
+            Assert.Throws<IOException>(() => fileSystem.Directory.ResolveLinkTarget(previousPath, true));
+        }
+
+        [Test]
+        public void MockDirectory_ResolveLinkTarget_WithoutFinalTarget_ShouldReturnFirstLink()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+            fileSystem.Directory.CreateSymbolicLink("foo1", "foo");
+
+            var result = fileSystem.Directory.ResolveLinkTarget("foo1", false);
+
+            Assert.AreEqual("foo", result.Name);
+        }
+
+        [Test]
+        public void MockDirectory_ResolveLinkTarget_WithoutTargetLink_ShouldThrowIOException()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.Directory.CreateDirectory("bar");
+            fileSystem.Directory.CreateSymbolicLink("foo", "bar");
+
+            Assert.Throws<IOException>(() =>
+            {
+                fileSystem.Directory.ResolveLinkTarget("bar", false);
+            });
+        }
 #endif
     }
 }
diff --git a/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockFileInfoSymlinkTests.cs b/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockFileInfoSymlinkTests.cs
diff --git a/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockFileSymlinkTests.cs b/tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockFileSymlinkTests.cs

Original file line number	Diff line number	Diff line change
`@@ -52,7 +52,7 @@ public MockDirectoryInfo(IMockFileDataAccessor mockFileDataAccessor, string dire`
`52`	`52`	`/// <inheritdoc />`
`53`	`53`	`public override void CreateAsSymbolicLink(string pathToTarget)`
`54`	`54`	`{`
`55`		`- throw CommonExceptions.NotImplemented();`
	`55`	`+ FileSystem.Directory.CreateSymbolicLink(FullName, pathToTarget);`
`56`	`56`	`}`
`57`	`57`	`#endif`
`58`	`58`
`@@ -74,7 +74,7 @@ public override void Refresh()`
`74`	`74`	`/// <inheritdoc />`
`75`	`75`	`public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)`
`76`	`76`	`{`
`77`		`- throw CommonExceptions.NotImplemented();`
	`77`	`+ return FileSystem.Directory.ResolveLinkTarget(FullName, returnFinalTarget);`
`78`	`78`	`}`
`79`	`79`	`#endif`
`80`	`80`
Original file line number	Diff line number	Diff line change
`@@ -29,7 +29,7 @@ public MockFileInfo(IMockFileDataAccessor mockFileSystem, string path) : base(mo`
`29`	`29`	`/// <inheritdoc />`
`30`	`30`	`public override void CreateAsSymbolicLink(string pathToTarget)`
`31`	`31`	`{`
`32`		`- throw CommonExceptions.NotImplemented();`
	`32`	`+ FileSystem.File.CreateSymbolicLink(FullName, pathToTarget);`
`33`	`33`	`}`
`34`	`34`	`#endif`
`35`	`35`
`@@ -51,7 +51,7 @@ public override void Refresh()`
`51`	`51`	`/// <inheritdoc />`
`52`	`52`	`public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)`
`53`	`53`	`{`
`54`		`- throw CommonExceptions.NotImplemented();`
	`54`	`+ return FileSystem.File.ResolveLinkTarget(FullName, returnFinalTarget);`
`55`	`55`	`}`
`56`	`56`	`#endif`
`57`	`57`
Original file line number	Diff line number	Diff line change
`@@ -22,7 +22,7 @@ public DirectoryInfoWrapper(IFileSystem fileSystem, DirectoryInfo instance) : ba`
`22`	`22`	`/// <inheritdoc />`
`23`	`23`	`public override void CreateAsSymbolicLink(string pathToTarget)`
`24`	`24`	`{`
`25`		`- throw new NotImplementedException();`
	`25`	`+ instance.CreateAsSymbolicLink(pathToTarget);`
`26`	`26`	`}`
`27`	`27`	`#endif`
`28`	`28`
`@@ -42,7 +42,8 @@ public override void Refresh()`
`42`	`42`	`/// <inheritdoc />`
`43`	`43`	`public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)`
`44`	`44`	`{`
`45`		`- throw new NotImplementedException();`
	`45`	`+ return instance.ResolveLinkTarget(returnFinalTarget)`
	`46`	`+ .WrapFileSystemInfo(FileSystem);`
`46`	`47`	`}`
`47`	`48`	`#endif`
`48`	`49`
Original file line number	Diff line number	Diff line change
`@@ -34,7 +34,8 @@ public override IDirectoryInfo CreateDirectory(string path, UnixFileMode unixCre`
`34`	`34`	`/// <inheritdoc />`
`35`	`35`	`public override IFileSystemInfo CreateSymbolicLink(string path, string pathToTarget)`
`36`	`36`	`{`
`37`		`- return Directory.CreateSymbolicLink(path, pathToTarget).WrapFileSystemInfo(FileSystem);`
	`37`	`+ return Directory.CreateSymbolicLink(path, pathToTarget)`
	`38`	`+ .WrapFileSystemInfo(FileSystem);`
`38`	`39`	`}`
`39`	`40`	`#endif`
`40`	`41`
`@@ -219,7 +220,8 @@ public override void Move(string sourceDirName, string destDirName)`
`219`	`220`	`/// <inheritdoc />`
`220`	`221`	`public override IFileSystemInfo ResolveLinkTarget(string linkPath, bool returnFinalTarget)`
`221`	`222`	`{`
`222`		- throw new NotSupportedException("TODO: Missing object implementing `IFileSystemInfo`");
	`223`	`+ return Directory.ResolveLinkTarget(linkPath, returnFinalTarget)`
	`224`	`+ .WrapFileSystemInfo(FileSystem);`
`223`	`225`	`}`
`224`	`226`	`#endif`
`225`	`227`
Original file line number	Diff line number	Diff line change
`@@ -39,7 +39,8 @@ public override void Refresh()`
`39`	`39`	`/// <inheritdoc />`
`40`	`40`	`public override IFileSystemInfo ResolveLinkTarget(bool returnFinalTarget)`
`41`	`41`	`{`
`42`		`- throw new NotImplementedException();`
	`42`	`+ return instance.ResolveLinkTarget(returnFinalTarget)`
	`43`	`+ .WrapFileSystemInfo(FileSystem);`
`43`	`44`	`}`
`44`	`45`	`#endif`
`45`	`46`
Original file line number	Diff line number	Diff line change
`@@ -79,7 +79,8 @@ public override FileSystemStream Create(string path, int bufferSize, FileOptions`
`79`	`79`	`/// <inheritdoc />`
`80`	`80`	`public override IFileSystemInfo CreateSymbolicLink(string path, string pathToTarget)`
`81`	`81`	`{`
`82`		`- return File.CreateSymbolicLink(path, pathToTarget).WrapFileSystemInfo(FileSystem);`
	`82`	`+ return File.CreateSymbolicLink(path, pathToTarget)`
	`83`	`+ .WrapFileSystemInfo(FileSystem);`
`83`	`84`	`}`
`84`	`85`	`#endif`
`85`	`86`	`/// <inheritdoc />`
`@@ -347,7 +348,8 @@ public override void Replace(string sourceFileName, string destinationFileName,`
`347`	`348`	`/// <inheritdoc />`
`348`	`349`	`public override IFileSystemInfo ResolveLinkTarget(string linkPath, bool returnFinalTarget)`
`349`	`350`	`{`
`350`		`- throw new NotImplementedException();`
	`351`	`+ return File.ResolveLinkTarget(linkPath, returnFinalTarget)`
	`352`	`+ .WrapFileSystemInfo(FileSystem);`
`351`	`353`	`}`
`352`	`354`	`#endif`
`353`	`355`