Throw esplugin errors as system_error exceptions

Instead of FileAccessError, so that callers can use the exception's code to distinguish between different causes.

include/loot/exception/error_categories.h

@@ -30,6 +30,14 @@
 #include "loot/api_decorator.h"
 
 namespace loot {
+/**
+ * @brief Get the error category that can be used to identify system_error
+ *        exceptions that are due to esplugin errors.
+ * @returns A reference to the static object of unspecified runtime type,
+ *          derived from std::error_category.
+ */
+LOOT_API const std::error_category& esplugin_category();
+
 /**
  * @brief Get the error category that can be used to identify system_error
  *        exceptions that are due to libloadorder errors.

src/api/error_categories.cpp

@@ -28,6 +28,16 @@
 
 namespace loot {
 namespace detail {
+class esplugin_category : public std::error_category {
+  const char* name() const noexcept override { return "esplugin"; }
+
+  std::string message(int) const override { return "esplugin error"; }
+
+  bool equivalent(const std::error_code& code, int) const noexcept override {
+    return code.category().name() == name();
+  }
+};
+
 class libloadorder_category : public std::error_category {
   const char* name() const noexcept override { return "libloadorder"; }
 
@@ -39,6 +49,11 @@ class libloadorder_category : public std::error_category {
 };
 }
 
+LOOT_API const std::error_category& esplugin_category() {
+  static detail::esplugin_category instance;
+  return instance;
+}
+
 LOOT_API const std::error_category& libloadorder_category() {
   static detail::libloadorder_category instance;
   return instance;

src/api/plugin.cpp

@@ -33,6 +33,7 @@
 #include "api/helpers/crc.h"
 #include "api/helpers/logging.h"
 #include "api/helpers/text.h"
+#include "loot/exception/error_categories.h"
 #include "loot/exception/file_access_error.h"
 
 namespace loot {
@@ -201,7 +202,7 @@ void HandleEspluginError(const std::string& operation,
     logger->error(err);
   }
 
-  throw FileAccessError(err);
+  throw std::system_error(returnCode, esplugin_category(), err);
 }
 
 Plugin::Plugin(const GameType gameType,
@@ -239,6 +240,18 @@ Plugin::Plugin(const GameType gameType,
     }
 
     tags_ = ExtractBashTags(GetDescription());
+  } catch (const std::system_error& e) {
+    if (e.code().category() == esplugin_category()) {
+      throw;
+    }
+
+    if (logger) {
+      logger->error("Cannot read plugin file \"{}\". Details: {}",
+                    pluginPath.u8string(),
+                    e.what());
+    }
+    throw FileAccessError("Cannot read \"" + pluginPath.u8string() +
+                          "\". Details: " + e.what());
   } catch (const std::exception& e) {
     if (logger) {
       logger->error("Cannot read plugin file \"{}\". Details: {}",

src/tests/api/internals/game/game_test.h

@@ -26,6 +26,7 @@ along with LOOT.  If not, see
 #define LOOT_TESTS_API_INTERNALS_GAME_GAME_TEST
 
 #include "api/game/game.h"
+#include "loot/exception/error_categories.h"
 #include "tests/common_game_test_fixture.h"
 
 namespace loot {
@@ -363,6 +364,31 @@ TEST_P(GameTest, loadPluginsShouldUseAbsolutePathsAsGiven) {
   EXPECT_NE(nullptr, game.GetPlugin(blankEsm));
 }
 
+TEST_P(
+    GameTest,
+    loadPluginsShouldThrowIfFullyLoadingAPluginWithAMissingMasterIfGameIsMorrowindOrStarfield) {
+  Game game = Game(GetParam(), dataPath.parent_path(), localPath);
+
+  const auto pluginName =
+      GetParam() == GameType::starfield ? blankFullEsm : blankEsm;
+
+  std::filesystem::remove(dataPath / pluginName);
+
+  if (GetParam() == GameType::tes3 || GetParam() == GameType::starfield) {
+    try {
+      game.LoadPlugins({blankMasterDependentEsm}, false);
+      FAIL(); 
+    } catch (const std::system_error& e) {
+      EXPECT_EQ(ESP_ERROR_PLUGIN_METADATA_NOT_FOUND, e.code().value());
+      EXPECT_EQ(esplugin_category(), e.code().category());
+    }
+  } else {
+    game.LoadPlugins({blankMasterDependentEsm}, false);
+
+    EXPECT_NE(nullptr, game.GetPlugin(blankMasterDependentEsm));
+  }
+}
+
 TEST_P(GameTest, sortPluginsShouldHandlePluginPathsThatAreNotJustFilenames) {
   Game game = Game(GetParam(), dataPath.parent_path(), localPath);
 

src/tests/api/internals/plugin_test.h

@@ -27,6 +27,7 @@ along with LOOT.  If not, see
 
 #include "api/game/game.h"
 #include "api/plugin.h"
+#include "loot/exception/error_categories.h"
 #include "tests/common_game_test_fixture.h"
 
 namespace loot {
@@ -337,8 +338,7 @@ TEST_P(
             plugin3.IsLightPlugin());
 }
 
-TEST_P(
-  PluginTest,
+TEST_P(PluginTest,
        isMediumPluginShouldBeTrueForAMediumFlaggedPluginForStarfield) {
   if (GetParam() != GameType::starfield) {
     auto bytes = ReadFile(dataPath / blankEsm);
@@ -348,14 +348,13 @@ TEST_P(
 
   const auto pluginName =
       GetParam() == GameType::starfield ? blankMediumEsm : blankEsm;
-  Plugin plugin(game_.GetType(), game_.GetCache(), game_.DataPath() / pluginName,
-                true);
+  Plugin plugin(
+      game_.GetType(), game_.GetCache(), game_.DataPath() / pluginName, true);
 
   EXPECT_EQ(GetParam() == GameType::starfield, plugin.IsMediumPlugin());
 }
 
-TEST_P(PluginTest,
-       isUpdatePluginShouldOnlyBeTrueForAStarfieldUpdatePlugin) {
+TEST_P(PluginTest, isUpdatePluginShouldOnlyBeTrueForAStarfieldUpdatePlugin) {
   auto bytes = ReadFile(dataPath / blankMasterDependentEsp);
   bytes[9] = 0x2;
   WriteFile(dataPath / blankMasterDependentEsp, bytes);
@@ -385,11 +384,16 @@ TEST_P(PluginTest, loadingAPluginWithMastersShouldReadThemCorrectly) {
 }
 
 TEST_P(PluginTest, loadingAPluginThatDoesNotExistShouldThrow) {
-  EXPECT_THROW(Plugin(game_.GetType(),
-                      game_.GetCache(),
-                      game_.DataPath() / "Blank\\.esp",
-                      true),
-               FileAccessError);
+  try {
+    Plugin(game_.GetType(),
+           game_.GetCache(),
+           game_.DataPath() / "Blank\\.esp",
+           true);
+    FAIL();
+  } catch (const std::system_error& e) {
+    EXPECT_EQ(ESP_ERROR_FILE_NOT_FOUND, e.code().value());
+    EXPECT_EQ(esplugin_category(), e.code().category());
+  }
 }
 
 TEST_P(
@@ -545,8 +549,7 @@ TEST_P(
     PluginTest,
     isValidAsMediumPluginShouldReturnTrueOnlyForAStarfieldPluginWithNewFormIdsBetween0And0xFFFFInclusive) {
   bool valid =
-      Plugin(
-          game_.GetType(), game_.GetCache(), dataPath / blankEsm, true)
+      Plugin(game_.GetType(), game_.GetCache(), dataPath / blankEsm, true)
           .IsValidAsMediumPlugin();
   if (GetParam() == GameType::starfield) {
     EXPECT_TRUE(valid);
@@ -558,12 +561,11 @@ TEST_P(
 TEST_P(
     PluginTest,
     IsValidAsUpdatePluginShouldOnlyReturnTrueForAStarfieldPluginWithNoNewRecords) {
-  const auto sourcePluginName = GetParam() == GameType::starfield
-                                  ? blankFullEsm
-                                  : blankEsp;
+  const auto sourcePluginName =
+      GetParam() == GameType::starfield ? blankFullEsm : blankEsp;
   const auto updatePluginName = GetParam() == GameType::starfield
-                                  ? blankMasterDependentEsp
-                                  : blankDifferentPluginDependentEsp;
+                                    ? blankMasterDependentEsp
+                                    : blankDifferentPluginDependentEsp;
 
   Plugin plugin1(game_.GetType(),
                  game_.GetCache(),
@@ -583,8 +585,7 @@ TEST_P(
   }
 
   EXPECT_FALSE(plugin1.IsValidAsUpdatePlugin());
-  EXPECT_EQ(GetParam() == GameType::starfield,
-            plugin2.IsValidAsUpdatePlugin());
+  EXPECT_EQ(GetParam() == GameType::starfield, plugin2.IsValidAsUpdatePlugin());
 }
 
 TEST_P(PluginTest,