fix(windows): unhandled exception thrown in std::_Xlen_string() (#288)

Current working directory when running tests (with `VSTest.Console.exe`)
changed between Visual Studio 16.8 and 16.9 and broke our pipelines. To
prevent future build failures, we'll use the absolute path to the test
source file to build the path to the test fixtures.

.github/workflows/build.yml

@@ -368,7 +368,7 @@ jobs:
     steps:
       - name: Set up MSBuild
         uses: microsoft/setup-msbuild@v1.0.2
-      - name: Setup VSTest.console.exe
+      - name: Set up VSTest.console.exe
         uses: darenm/Setup-VSTest@v1
       - name: Set up Node.js
         uses: actions/setup-node@v1

example/windows/ReactTestAppTests/ManifestTests.cpp

@@ -8,6 +8,7 @@
 #include "pch.h"
 
 #include <CppUnitTest.h>
+#include <filesystem>
 #include <string>
 
 #include "Manifest.h"
@@ -17,6 +18,19 @@ using namespace Microsoft::VisualStudio::CppUnitTestFramework;
 using ReactTestApp::Component;
 using ReactTestApp::Manifest;
 
+std::string fixturePath(std::filesystem::path file)
+{
+    // Current working directory when running tests (with VSTest.Console.exe)
+    // changed between Visual Studio 16.8 and 16.9 and broke our pipelines. To
+    // prevent future build failures, we'll use the absolute path to this
+    // source file to build the path to the test fixtures.
+    //
+    // To ensure that `__FILE__` is a full path, we must also enable `/FC` in
+    // Properties > C/C++ > Advanced.
+    const auto p = std::filesystem::path(__FILE__).replace_filename("manifestTestFiles") / file;
+    return p.string();
+}
+
 // disable clang-format because it doesn't handle macros very well
 // clang-format off
 namespace ReactTestAppTests
@@ -26,7 +40,7 @@ namespace ReactTestAppTests
     public:
         TEST_METHOD(ParseManifestWithOneComponent)
         {
-            auto result = ReactTestApp::GetManifest("manifestTestFiles/simpleManifest.json");
+            auto result = ReactTestApp::GetManifest(fixturePath("simpleManifest.json"));
             if (!result.has_value()) {
                 Assert::Fail(L"Couldn't read manifest file");
             }
@@ -42,7 +56,7 @@ namespace ReactTestAppTests
 
         TEST_METHOD(ParseManifestWithMultipleComponents)
         {
-            auto result = ReactTestApp::GetManifest("manifestTestFiles/withMultipleComponents.json");
+            auto result = ReactTestApp::GetManifest(fixturePath("withMultipleComponents.json"));
             if (!result.has_value()) {
                 Assert::Fail(L"Couldn't read manifest file");
             }
@@ -67,7 +81,7 @@ namespace ReactTestAppTests
 
         TEST_METHOD(ParseManifestWithComplexInitialProperties)
         {
-            auto result = ReactTestApp::GetManifest("manifestTestFiles/withComplexInitialProperties.json");
+            auto result = ReactTestApp::GetManifest(fixturePath("withComplexInitialProperties.json"));
             if (!result.has_value()) {
                 Assert::Fail(L"Couldn't read manifest file");
             }

windows/ReactTestApp/Manifest.cpp

@@ -9,8 +9,7 @@
 
 #include "Manifest.h"
 
-#include <fstream>
-#include <iostream>
+#include <cstdio>
 
 #include <nlohmann/json.hpp>
 #include <winrt/Windows.Security.Cryptography.Core.h>
@@ -116,17 +115,19 @@ namespace ReactTestApp
 
     std::optional<std::pair<Manifest, std::string>> GetManifest(std::string const &filename)
     {
-        std::string json;
-        {
-            std::ifstream stream(filename);
-
-            stream.seekg(0, std::ios::end);
-            json.reserve(static_cast<size_t>(stream.tellg()));
-
-            stream.seekg(0, std::ios::beg);
-            json.assign(std::istreambuf_iterator<char>(stream), {});
+        std::FILE *stream = nullptr;
+        if (fopen_s(&stream, filename.c_str(), "rb") != 0) {
+            return std::nullopt;
         }
 
+        std::string json;
+        std::fseek(stream, 0, SEEK_END);
+        json.resize(std::ftell(stream));
+
+        std::rewind(stream);
+        std::fread(json.data(), 1, json.size(), stream);
+        std::fclose(stream);
+
         auto j = nlohmann::json::parse(json, nullptr, false);
         if (j.is_discarded()) {
             return std::nullopt;