feat: default fromPath for problem matchers (#3802)

src/Test/L0/Worker/OutputManagerL0.cs

@@ -937,6 +937,62 @@ namespace GitHub.Runner.Common.Tests.Worker
             }
         }
 
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async void MatcherDefaultFromPath()
+        {
+            var matchers = new IssueMatchersConfig
+            {
+                Matchers =
+                {
+                    new IssueMatcherConfig
+                    {
+                        Owner = "my-matcher-1",
+                        FromPath = "workflow-repo/some-project/some-project.proj",
+                        Patterns = new[]
+                        {
+                            new IssuePatternConfig
+                            {
+                                Pattern = @"(.+): (.+)",
+                                File = 1,
+                                Message = 2,
+                            },
+                        },
+                    },
+                },
+            };
+            using (var hostContext = Setup(matchers: matchers))
+            using (_outputManager)
+            {
+                // Setup github.workspace, github.repository
+                var workDirectory = hostContext.GetDirectory(WellKnownDirectory.Work);
+                ArgUtil.NotNullOrEmpty(workDirectory, nameof(workDirectory));
+                Directory.CreateDirectory(workDirectory);
+                var workspaceDirectory = Path.Combine(workDirectory, "workspace");
+                Directory.CreateDirectory(workspaceDirectory);
+                _executionContext.Setup(x => x.GetGitHubContext("workspace")).Returns(workspaceDirectory);
+                _executionContext.Setup(x => x.GetGitHubContext("repository")).Returns("my-org/workflow-repo");
+
+                // Setup a git repository
+                var repositoryPath = Path.Combine(workspaceDirectory, "workflow-repo");
+                await CreateRepository(hostContext, repositoryPath, "https://github.com/my-org/workflow-repo");
+
+                // Create a test file
+                var filePath = Path.Combine(repositoryPath, "some-project", "some-directory", "some-file.txt");
+                Directory.CreateDirectory(Path.GetDirectoryName(filePath));
+                File.WriteAllText(filePath, "");
+
+                // Process
+                Process("some-directory/some-file.txt: some error");
+                Assert.Equal(1, _issues.Count);
+                Assert.Equal("some error", _issues[0].Item1.Message);
+                Assert.Equal("some-project/some-directory/some-file.txt", _issues[0].Item1.Data["file"]);
+                Assert.Equal(0, _commands.Count);
+                Assert.Equal(0, _messages.Count);
+            }
+        }
+
         [Fact]
         [Trait("Level", "L0")]
         [Trait("Category", "Worker")]