Checking PATH environment variable (#2107)

* Checking PATH environment variable

* creating file searcher helper, adding tests

* code review & update in changelog

* updating error comment

* fixing tests

src/ReleaseHistory.md

@@ -5,6 +5,7 @@
 * DEPENDENCY BREAKING: SARIF now requires Newtonsoft.JSON 11.0.2 (rather than 10.0.3)
 * DEPENDENCY: SARIF TypeScript package now requires minimist 1.2.3 or later (rather than >=1.2.0)
 * FEATURE: Add a setter to `GitHelper.GitExePath`. [#2110](https://github.com/microsoft/sarif-sdk/pull/2110)
+* FEATURE: `GitHelper` will search in %PATH% variable if `git.exe` isn't located in ProgramFiles folder
 
 ## **v2.3.6** [Sdk](https://www.nuget.org/packages/Sarif.Sdk/2.3.6) | [Driver](https://www.nuget.org/packages/Sarif.Driver/2.3.6) | [Converters](https://www.nuget.org/packages/Sarif.Converters/2.3.6) | [Multitool](https://www.nuget.org/packages/Sarif.Multitool/2.3.6) | [Multitool Library](https://www.nuget.org/packages/Sarif.Multitool.Library/2.3.6)
 * BUGFIX: Restore multitool client app package build.

src/Sarif/FileSearcherHelper.cs

@@ -0,0 +1,51 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+
+namespace Microsoft.CodeAnalysis.Sarif
+{
+    internal static class FileSearcherHelper
+    {
+        /// <summary>
+        /// This method will search in the environment variable for a specific file name.
+        /// It will return the first file found.
+        /// </summary>
+        /// <param name="environmentVariable">Environment variable that we will look for</param>
+        /// <param name="fileName">Name of the file that we will look for in the environment variable</param>
+        /// <returns>Path to the file name or empty string.</returns>
+        public static string SearchForFileInEnvironmentVariable(string environmentVariable, string fileName)
+        {
+            string variable = Environment.GetEnvironmentVariable(environmentVariable);
+            if (string.IsNullOrEmpty(variable))
+            {
+                return null;
+            }
+
+            string[] paths = variable.Split(';');
+            foreach (string path in paths)
+            {
+                string returnedPath = SearchForFileNameInPath(path, fileName);
+                if (!string.IsNullOrEmpty(returnedPath))
+                {
+                    return returnedPath;
+                }
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// This method will search for a file name in a specific path.
+        /// </summary>
+        /// <param name="path">Path where it will search.</param>
+        /// <param name="fileName">Name of the file that it will search</param>
+        /// <returns>Path to the file name or empty string.</returns>
+        public static string SearchForFileNameInPath(string path, string fileName)
+        {
+            string filePath = $@"{path}\{fileName}";
+            return File.Exists(filePath) ? filePath : null;
+        }
+    }
+}

src/Sarif/GitHelper.cs

@@ -73,8 +73,15 @@ public void Checkout(string repoPath, string commitSha)
                 args: $"checkout {commitSha}");
         }
 
-        private string GetGitExePath()
-            => this.fileSystem.FileExists(s_expectedGitExePath) ? s_expectedGitExePath : null;
+        internal string GetGitExePath()
+        {
+            if (this.fileSystem.FileExists(s_expectedGitExePath))
+            {
+                return s_expectedGitExePath;
+            }
+
+            return FileSearcherHelper.SearchForFileInEnvironmentVariable("PATH", "git.exe");
+        }
 
         public string GetCurrentBranch(string repoPath)
         {

src/Test.UnitTests.Sarif/GitHelperTests.cs

@@ -118,6 +118,49 @@ public void GetRepositoryRoot_WhenCalledOnTheDefaultInstanceWithCachingDisabled_
             action.Should().NotThrow();
         }
 
+        [Fact]
+        public void GetGitExePath_WhenPathExistsInProgramFiles()
+        {
+            var mockFileSystem = new Mock<IFileSystem>();
+
+            mockFileSystem.Setup(x => x.FileExists(It.IsAny<string>())).Returns(true);
+
+            var gitHelper = new GitHelper(mockFileSystem.Object);
+
+            gitHelper.GetGitExePath().Should().NotBeNullOrEmpty();
+        }
+
+        [Fact]
+        public void GetGitExePath_WhenPathDoesNotExistInProgramFiles()
+        {
+            var mockFileSystem = new Mock<IFileSystem>();
+
+            mockFileSystem.Setup(x => x.FileExists(It.IsAny<string>())).Returns(false);
+
+            var gitHelper = new GitHelper(mockFileSystem.Object);
+
+            gitHelper.GetGitExePath().Should().NotBeNull();
+        }
+
+        [Fact]
+        public void SearchForFileInEnvironmentVariable_WhenVariableDoesNotExist()
+        {
+            FileSearcherHelper.SearchForFileInEnvironmentVariable("PATH_THAT_DOES_NOT_EXIST", "filename.exe").Should().BeNull();
+        }
+
+        [Fact]
+        public void SearchForFileInEnvironmentVariable_WhenVariableExistsButFileDoesnt()
+        {
+            // The error in the ntdll name here is intentional.
+            FileSearcherHelper.SearchForFileInEnvironmentVariable("PATH", "ntdll.dlll").Should().BeNull();
+        }
+
+        [Fact]
+        public void SearchForFileInEnvironmentVariable_WhenVariableAndFileExists()
+        {
+            FileSearcherHelper.SearchForFileInEnvironmentVariable("PATH", "ntdll.dll").Should().NotBeNull();
+        }
+
         [Fact]
         public void GitExePath_WhenPathDoesntExist_SettingManuallyShouldWork()
         {