core: report plugin command exceptions instead of crashing the game

docs/changelog.txt

@@ -63,6 +63,7 @@ Template for new versions:
 - `stocks`: the overlay's ``collapse all`` hotkey now toggles, expanding all categories again when everything is collapsed
 
 ## Fixes
+- Plugin commands that throw uncaught C++ exceptions now report an error instead of crashing the game
 - Fix broken weather lookup in ``World::ReadCurrentWeather``
 - Fixed a possible hang or assertion failure when pressing a hotkey while a DFHack GUI window was open but unfocused
 - In ``Screen`` module, Fix out-of-bounds color table access when Lua pens use ``COLOR_RESET``

library/PluginManager.cpp

@@ -494,6 +494,19 @@ command_result Plugin::invoke(color_ostream &out, const std::string & command, s
         if (auto cmdIt = std::ranges::find_if(commands, [&](const PluginCommand &cmd) { return cmd.name == command; });
             commands.end() != cmdIt)
         {
+            // an uncaught exception from a plugin command would propagate
+            // through runCommand and terminate the game; report it instead
+            auto call = [&]() -> command_result {
+                try {
+                    return cmdIt->function(out, parameters);
+                } catch (const std::exception &e) {
+                    out.printerr("Exception in {} command '{}': {}\n", name, command, e.what());
+                    return CR_FAILURE;
+                } catch (...) {
+                    out.printerr("Exception in {} command '{}'\n", name, command);
+                    return CR_FAILURE;
+                }
+            };
             // running interactive things from some other source than the console would break it
             if (!out.is_console() && cmdIt->interactive)
                 cr = CR_NEEDS_CONSOLE;
@@ -504,15 +517,15 @@ command_result Plugin::invoke(color_ostream &out, const std::string & command, s
                     cr = CR_WRONG_USAGE;
                 }
                 else {
-                    cr = cmdIt->function(out, parameters);
+                    cr = call();
                 }
             }
             else if (cmdIt->unlocked) {
-                cr = cmdIt->function(out, parameters);
+                cr = call();
             }
             else {
                 CoreSuspender suspend;
-                cr = cmdIt->function(out, parameters);
+                cr = call();
             }
         }
     }

plugins/devel/kittens.cpp

@@ -53,6 +53,7 @@ uint64_t timeLast = 0;
 
 command_result kittens (color_ostream &out, vector <string> & parameters);
 command_result ktimer (color_ostream &out, vector <string> & parameters);
+command_result throwtest (color_ostream &out, vector <string> & parameters);
 command_result trackmenu (color_ostream &out, vector <string> & parameters);
 command_result trackpos (color_ostream &out, vector <string> & parameters);
 command_result trackstate (color_ostream &out, vector <string> & parameters);
@@ -68,6 +69,7 @@ DFhackCExport command_result plugin_init ( color_ostream &out, std::vector <Plug
     commands.push_back(PluginCommand("trackstate","Track world and map state (toggle).",trackstate));
     commands.push_back(PluginCommand("colormods","Dump colormod vectors.",colormods));
     commands.push_back(PluginCommand("sharedsignal","Test Signal with signal_shared_tag",sharedsignal));
+    commands.push_back(PluginCommand("throwtest","Throw an exception to test command error handling.",throwtest));
     return CR_OK;
 }
 
@@ -377,6 +379,13 @@ command_result sharedsignal (color_ostream &out, vector <string> & parameters)
     return CR_OK;
 }
 
+command_result throwtest (color_ostream &out, vector <string> & parameters)
+{
+    if (!parameters.empty() && parameters[0] == "nonstd")
+        throw 42;
+    throw std::runtime_error("throwtest: test exception");
+}
+
 command_result kittens (color_ostream &out, vector <string> & parameters)
 {
     if (parameters.size() >= 1)

test/plugins/kittens.lua

@@ -0,0 +1,31 @@
+config.mode = 'fortress'
+config.target = 'kittens'
+
+-- kittens is a developer plugin and is not built unless BUILD_DEV_PLUGINS is
+-- on, so these tests are skipped on builds where throwtest is unavailable
+local function has_throwtest()
+    for _, plugin in ipairs(dfhack.internal.listPlugins()) do
+        if plugin == 'kittens' then
+            for _, command in ipairs(dfhack.internal.listCommands(plugin)) do
+                if command == 'throwtest' then
+                    return true
+                end
+            end
+        end
+    end
+    return false
+end
+
+function test.exception_returns_failure()
+    if not has_throwtest() then return end
+    local output, status = dfhack.run_command_silent('throwtest')
+    expect.eq(CR_FAILURE, status)
+    expect.str_find('test exception', output)
+end
+
+function test.nonstd_exception_returns_failure()
+    if not has_throwtest() then return end
+    local output, status = dfhack.run_command_silent('throwtest nonstd')
+    expect.eq(CR_FAILURE, status)
+    expect.str_find("Exception in kittens command", output)
+end