Update runtimeconfig.json and deps.json paths when these break past the MAX_PATH threshold

src/installer/tests/HostActivation.Tests/PortableAppActivation.cs

@@ -332,6 +332,37 @@ public void AppHost_FrameworkDependent_GlobalLocation_Succeeds(bool useRegistere
             }
         }
 
+        [Fact]
+        public void RuntimeConfig_FilePath_Breaks_MAX_PATH_Threshold()
+        {
+            var project = sharedTestState.PortableAppFixture_Published
+                .Copy();
+
+            var appExeName = Path.GetFileName(project.TestProject.AppExe);
+            var outputDir = project.TestProject.OutputDirectory;
+
+            // Move the portable app to a path such that the length of the executable's fullpath
+            // is just 1 char behind MAX_PATH (260) so that the runtimeconfig(.dev).json files
+            // break this threshold. This will cause hostfxr to normalize these paths -- here we
+            // are checking that the updated paths are used.
+            var tmp = Path.GetTempPath();
+            var dirName = new string('a', 259 - tmp.Length - appExeName.Length - 1);
+            var newDir = Path.Combine(tmp, dirName);
+            var appExe = Path.Combine(newDir, appExeName);
+            Debug.Assert(appExe.Length == 259);
+            Directory.CreateDirectory(newDir);
+            foreach (var file in Directory.GetFiles(outputDir, "*.*", SearchOption.TopDirectoryOnly))
+                File.Copy(file, Path.Combine(newDir, Path.GetFileName(file)), true);
+
+            Command.Create(appExe)
+                .DotNetRoot(project.BuiltDotnet.BinPath)
+                .EnableTracingAndCaptureOutputs()
+                .MultilevelLookup(false)
+                .Execute()
+                .Should().Pass()
+                .And.HaveStdOutContaining("Hello World");
+        }
+
         [Fact]
         public void ComputedTPADoesntEndWithPathSeparator()
         {
@@ -699,7 +730,7 @@ public SharedTestState()
 
                 PortableAppFixture_Published = new TestProjectFixture("PortableApp", RepoDirectories)
                     .EnsureRestored()
-                    .PublishProject();
+                    .PublishProject(extraArgs: "/p:UseAppHost=true");
 
                 MockApp = new TestApp(SharedFramework.CalculateUniqueTestDirectory(Path.Combine(TestArtifact.TestArtifactsPath, "portableAppActivation")), "App");
                 Directory.CreateDirectory(MockApp.Location);

src/native/corehost/deps_format.cpp

@@ -439,7 +439,7 @@ bool deps_json_t::has_package(const pal::string_t& name, const pal::string_t& ve
 bool deps_json_t::load(bool is_framework_dependent, const pal::string_t& deps_path, const rid_fallback_graph_t& rid_fallback_graph)
 {
     m_deps_file = deps_path;
-    m_file_exists = bundle::info_t::config_t::probe(deps_path) || pal::file_exists(deps_path);
+    m_file_exists = bundle::info_t::config_t::probe(deps_path) || pal::realpath(&m_deps_file, true);
 
     json_parser_t json;
     if (!m_file_exists)
@@ -449,7 +449,7 @@ bool deps_json_t::load(bool is_framework_dependent, const pal::string_t& deps_pa
         return true;
     }
 
-    if (!json.parse_file(deps_path))
+    if (!json.parse_file(m_deps_file))
     {
         return false;
     }

src/native/corehost/hostmisc/pal.windows.cpp

@@ -645,11 +645,15 @@ bool pal::clr_palstring(const char* cstr, pal::string_t* out)
 // Return if path is valid and file exists, return true and adjust path as appropriate.
 bool pal::realpath(string_t* path, bool skip_error_logging)
 {
+    if (path->empty())
+    {
+        return false;
+    }
+
     if (LongFile::IsNormalized(*path))
     {
         WIN32_FILE_ATTRIBUTE_DATA data;
-        if (path->empty() // An empty path doesn't exist
-            || GetFileAttributesExW(path->c_str(), GetFileExInfoStandard, &data) != 0)
+        if (GetFileAttributesExW(path->c_str(), GetFileExInfoStandard, &data) != 0)
         {
             return true;
         }
@@ -713,11 +717,6 @@ bool pal::realpath(string_t* path, bool skip_error_logging)
 
 bool pal::file_exists(const string_t& path)
 {
-    if (path.empty())
-    {
-        return false;
-    }
-
     string_t tmp(path);
     return pal::realpath(&tmp, true);
 }

src/native/corehost/runtime_config.cpp

@@ -334,9 +334,9 @@ bool runtime_config_t::ensure_dev_config_parsed()
     trace::verbose(_X("Attempting to read dev runtime config: %s"), m_dev_path.c_str());
 
     pal::string_t retval;
-    if (!pal::file_exists(m_dev_path))
+    if (!pal::realpath(&m_dev_path, true))
     {
-        // Not existing is valid.
+        // It is valid for the runtimeconfig.dev.json to not exist.
         return true;
     }
 
@@ -402,7 +402,7 @@ bool runtime_config_t::ensure_parsed()
         trace::verbose(_X("Did not successfully parse the runtimeconfig.dev.json"));
     }
 
-    if (!bundle::info_t::config_t::probe(m_path) && !pal::file_exists(m_path))
+    if (!bundle::info_t::config_t::probe(m_path) && !pal::realpath(&m_path, true))
     {
         // Not existing is not an error.
         return true;