Stop Malformed Network Responses from Crashing the App

Duet, MKS and UltiMaker parsed print host replies with boost read_json
inside the HTTP completion callback with no try, so an HTML or truncated
reply threw out of the Physical Printer Test button and terminated the app,
or killed the upload queue thread. The five identical copies of the parser
(ESP3D's and Flashforge's were unused) are replaced by one shared
PrintHost::get_err_code_from_body that reports a non-JSON reply as an error.
The upload queue now catches a failing job per job, so one bad upload no
longer leaves later jobs queued forever.

Flashforge read material station slots with nlohmann value(), which throws
on off-type fields or non-object entries. The parsing moves into
Flashforge::parse_material_slots, which reads fields leniently with the
existing try_parse_json_int and skips bad entries.

UserManager::parse_json parsed the payload before its try block; the parse
now happens inside it.

src/libslic3r/GCode.cpp

@@ -2504,7 +2504,8 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessorResult* resu
 
     {
         LifecycleEventContext ctx;
-        ctx.name = std::to_string(print->model().id().id);
+        ctx.id = std::to_string(print->model().id().id);
+        ctx.name = print->get_model_name();
         ctx.code = LifecycleEvtCode::Ok;
         ctx.msg  = path;
         ctx.cancellation_check = [print]() { return print->canceled(); };
@@ -2556,7 +2557,8 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessorResult* resu
         }
         {
             LifecycleEventContext ctx;
-            ctx.name = std::to_string(print->model().id().id);
+            ctx.id = std::to_string(print->model().id().id);
+            ctx.name = print->get_model_name();
             ctx.code = LifecycleEvtCode::Error;
             ctx.msg  = std::string(path) + "\n" + err_msg;
             ctx.cancellation_check = [print]() { return print->canceled(); };
@@ -2580,7 +2582,8 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessorResult* resu
         boost::nowide::remove(path_tmp.c_str());
         {
             LifecycleEventContext ctx;
-            ctx.name = std::to_string(print->model().id().id);
+            ctx.id = std::to_string(print->model().id().id);
+            ctx.name = print->get_model_name();
             ctx.code = LifecycleEvtCode::Error;
             ctx.msg  = std::string(path) + "\n" + ex.what();
             ctx.cancellation_check = [print]() { return print->canceled(); };
@@ -2693,7 +2696,8 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessorResult* resu
     if (ret) {
         {
             LifecycleEventContext ctx;
-            ctx.name = std::to_string(print->model().id().id);
+            ctx.id = std::to_string(print->model().id().id);
+            ctx.name = print->get_model_name();
             ctx.code = LifecycleEvtCode::Error;
             ctx.msg  = std::string(path) + "\nFailed to rename the output G-code file: " + ret.message();
             ctx.cancellation_check = [print]() { return print->canceled(); };
@@ -2712,7 +2716,8 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessorResult* resu
 
     {
         LifecycleEventContext ctx;
-        ctx.name = std::to_string(print->model().id().id);
+        ctx.id = std::to_string(print->model().id().id);
+        ctx.name = print->get_model_name();
         ctx.code = LifecycleEvtCode::Ok;
         ctx.msg  = path;
         ctx.cancellation_check = [print]() { return print->canceled(); };

src/libslic3r/Print.cpp

@@ -2717,7 +2717,8 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
 
     {
         LifecycleEventContext ctx;
-        ctx.name = std::to_string(m_model.id().id);
+        ctx.id = std::to_string(m_model.id().id);
+        ctx.name = get_model_name();
         ctx.code = LifecycleEvtCode::Ok;
         ctx.cancellation_check = [this]() { return canceled(); };
         fire_lifecycle_event(LifecycleEvent::SliceStarted, ctx);
@@ -3344,7 +3345,8 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
 
     {
         LifecycleEventContext ctx;
-        ctx.name = std::to_string(m_model.id().id);
+        ctx.id = std::to_string(m_model.id().id);
+        ctx.name = get_model_name();
         ctx.code = LifecycleEvtCode::Ok;
         ctx.cancellation_check = [this]() { return canceled(); };
         fire_lifecycle_event(LifecycleEvent::SliceGeometryFinished, ctx);
@@ -4950,7 +4952,8 @@ void Print::export_gcode_from_previous_file(const std::string& file, GCodeProces
 {
     {
         LifecycleEventContext ctx;
-        ctx.name = std::to_string(m_model.id().id);
+        ctx.id = std::to_string(m_model.id().id);
+        ctx.name = get_model_name();
         ctx.code = LifecycleEvtCode::Ok;
         ctx.msg  = file;
         ctx.cancellation_check = [this]() { return canceled(); };
@@ -4980,7 +4983,8 @@ void Print::export_gcode_from_previous_file(const std::string& file, GCodeProces
         BOOST_LOG_TRIVIAL(error) << __FUNCTION__ <<  boost::format(": found errors when process gcode file %1%") %file.c_str();
         {
             LifecycleEventContext ctx;
-            ctx.name = std::to_string(m_model.id().id);
+            ctx.id = std::to_string(m_model.id().id);
+            ctx.name = get_model_name();
             ctx.code = LifecycleEvtCode::Error;
             ctx.msg  = file + "\n" + ex.what();
             ctx.cancellation_check = [this]() { return canceled(); };
@@ -4994,7 +4998,8 @@ void Print::export_gcode_from_previous_file(const std::string& file, GCodeProces
 
     {
         LifecycleEventContext ctx;
-        ctx.name = std::to_string(m_model.id().id);
+        ctx.id = std::to_string(m_model.id().id);
+        ctx.name = get_model_name();
         ctx.code = LifecycleEvtCode::Ok;
         ctx.msg  = file;
         ctx.cancellation_check = [this]() { return canceled(); };

src/slic3r/GUI/Plater.cpp

@@ -12800,8 +12800,6 @@ void Plater::priv::on_process_completed(SlicingProcessCompletedEvent &evt)
     notification_manager->set_slicing_progress_export_possible();
 
     // Reset the "export G-code path" name, so that the automatic background processing will be enabled again.
-    const std::string lifecycle_job_name = this->background_process.fff_print() ?
-        this->background_process.fff_print()->output_filename() : std::string();
     this->background_process.reset_export();
     // This bool stops showing export finished notification even when process_completed_with_error is false
     bool has_error = false;
@@ -12848,8 +12846,18 @@ void Plater::priv::on_process_completed(SlicingProcessCompletedEvent &evt)
 
     {
         Slic3r::LifecycleEventContext ctx;
-        ctx.name = lifecycle_job_name;
+        if (const PrintBase* print = this->background_process.current_print()) {
-        ctx.code = evt.cancelled() ? Slic3r::LifecycleEvtCode::Warn : (has_error ? Slic3r::LifecycleEvtCode::Error : Slic3r::LifecycleEvtCode::Ok);
+            const Model& model = print->model();
+            ctx.id             = std::to_string(model.id().id);
+            if (model.model_info)
+                ctx.name = model.model_info->model_name;
+        } else {
+            // Realistically Printbase* print will never be null because select_technology already asserts an active print
+            // and the worker thread asserts it before processing.
+            BOOST_LOG_TRIVIAL(warning) << __FUNCTION__ << ": slicing completed without an active print; lifecycle event has no model ID";
+        }
+        ctx.code = evt.cancelled() ? Slic3r::LifecycleEvtCode::Warn :
+                                     (has_error ? Slic3r::LifecycleEvtCode::Error : Slic3r::LifecycleEvtCode::Ok);
         ctx.msg  = evt.cancelled() ? "cancelled" : (has_error ? lifecycle_error_msg : std::string());
         Slic3r::fire_lifecycle_event(Slic3r::LifecycleEvent::SlicingJobComplete, ctx);
     }

src/slic3r/GUI/UserManager.cpp

@@ -31,14 +31,15 @@ int UserManager::parse_json(std::string payload)
 {
     bool restored_json = false;
     json j;
-    json j_pre = json::parse(payload);
-    if (j_pre.empty()) {
-        return -1;
-    }
 
     //bind/unbind
 
     try {
+        json j_pre = json::parse(payload);
+        if (j_pre.empty()) {
+            return -1;
+        }
+
         if (j_pre.contains("bind")) {
             if (j_pre["bind"].contains("command")) {
 

src/slic3r/Utils/Duet.cpp

@@ -274,13 +274,4 @@ bool Duet::start_print(wxString &msg, const std::string &filename, ConnectionTyp
 	return res;
 }
 
-int Duet::get_err_code_from_body(const std::string &body) const
-{
-	pt::ptree root;
-	std::istringstream iss (body); // wrap returned json to istringstream
-	pt::read_json(iss, root);
-
-	return root.get<int>("err", 0);
-}
-
 }

src/slic3r/Utils/Duet.hpp

@@ -40,7 +40,6 @@ private:
 	ConnectionType connect(wxString &msg) const;
 	void disconnect(ConnectionType connectionType) const;
 	bool start_print(wxString &msg, const std::string &filename, ConnectionType connectionType, bool simulationMode) const;
-	int get_err_code_from_body(const std::string &body) const;
 };
 
 }

src/slic3r/Utils/ESP3D.cpp

@@ -146,15 +146,6 @@ bool ESP3D::start_print(wxString& msg, const std::string& filename) const
     return ret;
 }
 
-int ESP3D::get_err_code_from_body(const std::string& body) const
-{
-    pt::ptree          root;
-    std::istringstream iss(body); // wrap returned json to istringstream
-    pt::read_json(iss, root);
-
-    return root.get<int>("err", 0);
-}
-
 // ESP3D only accepts 8.3 filenames else it crashes marlin and other undefined behaviour
 std::string ESP3D::get_short_name(const std::string& filename) const
 {

src/slic3r/Utils/ESP3D.hpp

@@ -33,7 +33,6 @@ private:
     std::string m_console_port;
 
     bool        start_print(wxString& msg, const std::string& filename) const;
-    int         get_err_code_from_body(const std::string& body) const;
     std::string get_short_name(const std::string& filename) const;
     std::string format_command(const std::string& path, const std::string& arg, const std::string& val) const;
 };

src/slic3r/Utils/Flashforge.cpp

@@ -510,12 +510,22 @@ bool Flashforge::fetch_material_slots(std::vector<FlashforgeMaterialSlot>& slots
     if (!request_local_api_json("detail", json{{"serialNumber", m_serial_number}, {"checkCode", m_check_code}}.dump(), body, msg))
         return false;
 
-    const auto parsed = json::parse(body, nullptr, false, true);
+    if (!parse_material_slots(body, slots, supports_material_station)) {
-    if (parsed.is_discarded()) {
         msg = _(L("Flashforge returned an invalid JSON response."));
         return false;
     }
 
+    return true;
+}
+
+bool Flashforge::parse_material_slots(const std::string& body, std::vector<FlashforgeMaterialSlot>& slots, bool* supports_material_station)
+{
+    slots.clear();
+
+    const auto parsed = json::parse(body, nullptr, false, true);
+    if (parsed.is_discarded())
+        return false;
+
     const auto& detail = parsed.contains("detail") ? parsed["detail"] : parsed;
     const auto& station = detail.contains("matlStationInfo") ? detail["matlStationInfo"] :
                           detail.contains("MatlStationInfo") ? detail["MatlStationInfo"] : json();
@@ -542,12 +552,21 @@ bool Flashforge::fetch_material_slots(std::vector<FlashforgeMaterialSlot>& slots
     if (supports_material_station != nullptr)
         *supports_material_station = reports_material_station;
 
+    // Fields are read leniently: firmware may send numbers as strings or flags as numbers.
     for (const auto& slot : slot_infos) {
+        if (!slot.is_object())
+            continue;
         FlashforgeMaterialSlot info;
-        info.slot_id        = slot.value("slotId", static_cast<int>(slots.size()) + 1);
+        info.slot_id = static_cast<int>(slots.size()) + 1;
-        info.has_filament   = slot.value("hasFilament", false);
+        if (const auto it = slot.find("slotId"); it != slot.end())
-        info.material_name  = slot.value("materialName", std::string());
+            try_parse_json_int(*it, info.slot_id);
-        info.material_color = slot.value("materialColor", std::string());
+        int has_filament = 0;
+        if (const auto it = slot.find("hasFilament"); it != slot.end() && try_parse_json_int(*it, has_filament))
+            info.has_filament = has_filament != 0;
+        if (const auto it = slot.find("materialName"); it != slot.end() && it->is_string())
+            info.material_name = it->get<std::string>();
+        if (const auto it = slot.find("materialColor"); it != slot.end() && it->is_string())
+            info.material_color = it->get<std::string>();
         slots.emplace_back(std::move(info));
     }
 
@@ -670,13 +689,4 @@ std::string Flashforge::extract_host_name() const
     return out;
 }
 
-int Flashforge::get_err_code_from_body(const std::string& body) const
-{
-    pt::ptree          root;
-    std::istringstream iss(body); // wrap returned json to istringstream
-    pt::read_json(iss, root);
-
-    return root.get<int>("err", 0);
-}
-
 } // namespace Slic3r

src/slic3r/Utils/Flashforge.hpp

@@ -45,6 +45,8 @@ public:
     PrintHostPostUploadActions get_post_upload_actions() const override { return PrintHostPostUploadAction::StartPrint; }
     std::string                get_host() const override { return m_host; }
     bool                       fetch_material_slots(std::vector<FlashforgeMaterialSlot>& slots, bool* supports_material_station, wxString& msg) const;
+    // Parses a local API "detail" reply. Returns false when the body is not valid JSON.
+    static bool                parse_material_slots(const std::string& body, std::vector<FlashforgeMaterialSlot>& slots, bool* supports_material_station);
     static bool                discover_printers(std::vector<FlashforgeDiscoveredPrinter>& printers, wxString& msg, int timeout_ms = 10000, int idle_timeout_ms = 1500, int max_retries = 3);
 
 private:
@@ -68,7 +70,6 @@ private:
     bool request_local_api_json(const std::string& path, const std::string& body, std::string& response_body, wxString& error_msg) const;
     std::string make_http_url(const std::string& path) const;
     std::string extract_host_name() const;
-    int  get_err_code_from_body(const std::string &body) const;
     bool connect(wxString& msg) const;
     bool start_print(wxString& msg, const std::string& filename) const;
 };

src/slic3r/Utils/MKS.cpp

@@ -141,13 +141,4 @@ bool MKS::start_print(wxString& msg, const std::string& filename) const
 	return ret;
 }
 
-int MKS::get_err_code_from_body(const std::string& body) const
-{
-	pt::ptree root;
-	std::istringstream iss(body); // wrap returned json to istringstream
-	pt::read_json(iss, root);
-
-	return root.get<int>("err", 0);
-}
-
 } // Slic3r

src/slic3r/Utils/MKS.hpp

@@ -34,7 +34,6 @@ private:
 
 	std::string get_upload_url(const std::string& filename) const;
 	bool start_print(wxString& msg, const std::string& filename) const;
-	int get_err_code_from_body(const std::string& body) const;
 };
 
 }

src/slic3r/Utils/PrintHost.cpp

@@ -3,10 +3,13 @@
 #include <vector>
 #include <thread>
 #include <exception>
+#include <sstream>
 #include <boost/optional.hpp>
 #include <boost/log/trivial.hpp>
 #include <boost/filesystem.hpp>
 #include <nlohmann/json.hpp>
+#include <boost/property_tree/ptree.hpp>
+#include <boost/property_tree/json_parser.hpp>
 
 #include <wx/string.h>
 #include <wx/app.h>
@@ -172,6 +175,20 @@ std::string moonraker_error_reason(const std::string &body)
 
 } // namespace
 
+int PrintHost::get_err_code_from_body(const std::string &body)
+{
+    boost::property_tree::ptree root;
+    std::istringstream iss(body);
+    try {
+        boost::property_tree::read_json(iss, root);
+    } catch (const std::exception &ex) {
+        BOOST_LOG_TRIVIAL(error) << "PrintHost: response is not valid JSON: " << ex.what();
+        return -1;
+    }
+
+    return root.get<int>("err", 0);
+}
+
 wxString PrintHost::format_error(const std::string &body, const std::string &error, unsigned status) const
 {
     if (status != 0) {
@@ -303,7 +320,12 @@ void PrintHostJobQueue::priv::bg_thread_main()
                 % job.cancelled;
 
             if (! job.cancelled) {
-                perform_job(std::move(job));
+                // A failing job must not stop the worker, or later jobs would stay queued forever.
+                try {
+                    perform_job(std::move(job));
+                } catch (const std::exception &e) {
+                    emit_error(e.what());
+                }
             }
 
             remove_source();

src/slic3r/Utils/PrintHost.hpp

@@ -87,6 +87,8 @@ public:
 
     static PrintHost* get_print_host(DynamicPrintConfig *config);
     static std::string get_print_host_webui(DynamicPrintConfig *config);
+    // Reads the "err" field of a JSON reply, 0 when absent. Returns -1 when the body is not valid JSON.
+    static int get_err_code_from_body(const std::string &body);
 
     //Support for cloud webui login
     virtual bool is_cloud() const { return false; }

src/slic3r/Utils/UltiMaker.cpp

@@ -654,13 +654,4 @@ bool UltiMaker::start_print(wxString &msg, const std::string &filename, Connecti
 	return res;
 }
 
-int UltiMaker::get_err_code_from_body(const std::string &body) const
-{
-	pt::ptree root;
-	std::istringstream iss (body); // wrap returned json to istringstream
-	pt::read_json(iss, root);
-
-	return root.get<int>("err", 0);
-}
-
 }

src/slic3r/Utils/UltiMaker.hpp

@@ -64,7 +64,6 @@ private:
 	void set_auth(Http& http) const;
 	void disconnect(ConnectionType connectionType) const;
 	bool start_print(wxString &msg, const std::string &filename, ConnectionType connectionType) const;
-	int get_err_code_from_body(const std::string &body) const;
 };
 
 }

tests/fff_print/test_print.cpp

@@ -15,6 +15,9 @@
 #include "libslic3r/Layer.hpp"
 #include "libslic3r/Model.hpp"
 #include "libslic3r/GCodeReader.hpp"
+#include "libslic3r/GCode/GCodeProcessor.hpp"
+#include "libslic3r/Exception.hpp"
+#include "libslic3r/LifecycleEvents.hpp"
 
 #include "test_helpers.hpp"
 #include "test_utils.hpp"
@@ -22,7 +25,10 @@
 #include <algorithm>
 #include <fstream>
 #include <iterator>
+#include <memory>
 #include <string_view>
+#include <utility>
+#include <vector>
 
 using namespace Slic3r;
 using namespace Slic3r::Test;
@@ -224,8 +230,88 @@ std::string resolved_output_name(Model& model, const std::string& format, const
     return print.output_filename(filename_base);
 }
 
+struct ScopedLifecycleHook
+{
+    explicit ScopedLifecycleHook(LifecycleHookFn hook) { set_lifecycle_hook_fn(std::move(hook)); }
+    ~ScopedLifecycleHook() { set_lifecycle_hook_fn(nullptr); }
+};
+
 } // namespace
 
+TEST_CASE("Slicing lifecycle events identify the model", "[Print][LifecycleEvents]")
+{
+    struct ObservedEvent {
+        LifecycleEvent event;
+        std::string id;
+        std::string name;
+    };
+    std::vector<ObservedEvent> events;
+    ScopedLifecycleHook hook([&](LifecycleEvent event, const LifecycleEventContext& ctx) {
+        events.push_back({ event, ctx.id, ctx.name });
+    });
+
+    Print print;
+    Model model;
+    ModelInfo info;
+    info.model_name = "Lifecycle test model";
+    model.model_info = std::make_shared<ModelInfo>(std::move(info));
+    init_print({cube(20)}, print, model);
+
+    print.process();
+    ScopedTemporaryFile temp(".gcode");
+    print.export_gcode(temp.string(), nullptr, nullptr);
+    GCodeProcessorResult result;
+    print.export_gcode_from_previous_file(temp.string(), &result);
+
+    const std::string expected_id = std::to_string(print.model().id().id);
+    const std::vector<LifecycleEvent> expected_events = {
+        LifecycleEvent::SliceStarted,
+        LifecycleEvent::SliceGeometryFinished,
+        LifecycleEvent::GCodeExportStarted,
+        LifecycleEvent::GCodeExportFinished,
+        LifecycleEvent::GCodeExportStarted,
+        LifecycleEvent::GCodeExportFinished,
+    };
+    REQUIRE(events.size() == expected_events.size());
+    for (size_t i = 0; i < expected_events.size(); ++i) {
+        CHECK(events[i].event == expected_events[i]);
+        CHECK(events[i].id == expected_id);
+        CHECK(events[i].name == "Lifecycle test model");
+    }
+}
+
+TEST_CASE("Slicing lifecycle event name is empty without model metadata", "[Print][LifecycleEvents]")
+{
+    std::string event_id;
+    std::string event_name = "unset";
+    ScopedLifecycleHook hook([&](LifecycleEvent event, const LifecycleEventContext& ctx) {
+        if (event == LifecycleEvent::SliceStarted) {
+            event_id = ctx.id;
+            event_name = ctx.name;
+        }
+    });
+
+    Print print;
+    Model model;
+    init_print({cube(20)}, print, model);
+    print.process();
+
+    CHECK(event_id == std::to_string(print.model().id().id));
+    CHECK(event_name.empty());
+}
+
+TEST_CASE("Output filenames with numeric statistics fail before slicing finishes", "[Print][Regression]")
+{
+    DynamicPrintConfig config = DynamicPrintConfig::full_print_config();
+    config.set_key_value("filename_format", new ConfigOptionString("{int(total_weight*10) / 10.0}"));
+
+    Print print;
+    Model model;
+    init_print({cube(20)}, print, model, config);
+
+    CHECK_THROWS_AS(print.output_filename(), PlaceholderParserError);
+}
+
 TEST_CASE("Print: {first_object_name} names the first printable object on the plate", "[Print]")
 {
     Model model;

tests/slic3rutils/CMakeLists.txt

@@ -25,6 +25,7 @@ add_executable(${_TEST_NAME}_tests
     test_plugin_cloud_metadata.cpp
     test_plugin_audit.cpp
     test_shortcuts.cpp
+    test_user_manager.cpp
     ../fff_print/test_helpers.cpp
     )
 

tests/slic3rutils/test_printhost.cpp

@@ -1,8 +1,12 @@
 #include <catch2/catch_all.hpp>
 
+#include <string>
+#include <vector>
+
 #include <nlohmann/json.hpp>
 
 #include "slic3r/Utils/PrintHost.hpp"
+#include "slic3r/Utils/Flashforge.hpp"
 
 using namespace Slic3r;
 
@@ -46,6 +50,14 @@ std::string moonraker_error(int code, const std::string& message, const std::str
 constexpr const char* k_busy_file_403 =
     R"JSON({"error": {"code": 403, "message": "Forbidden", "traceback": "Traceback (most recent call last):\n\n  File \"/home/lava/moonraker/moonraker/components/file_manager/file_manager.py\", line 1017, in _finish_gcode_upload\n    can_start = self._handle_operation_check(check_path)\n                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n\nmoonraker.utils.exceptions.ServerError: File currently in use\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n\n  File \"/home/lava/moonraker/moonraker/components/application.py\", line 1069, in post\n    raise tornado.web.HTTPError(\ntornado.web.HTTPError: HTTP 403: Forbidden (File is loaded, upload not permitted)\n"}})JSON";
 
+// Replies a print host can send instead of JSON: a proxy or login page, nothing, a cut-off body.
+const std::vector<std::string> non_json_replies = {
+    "<html><body>proxy login required</body></html>",
+    "",
+    "{\"err\":",
+    "{\"detail\":{\"matlStationInfo\":{\"slotInfos\":[{\"slotId\":1,",
+};
+
 } // namespace
 
 TEST_CASE("A Klipper upload error shows its reason instead of a Python traceback", "[PrintHost][Regression]")
@@ -211,3 +223,94 @@ TEST_CASE("Error bodies that are not a Moonraker envelope are left unchanged", "
         CHECK(format_error("", "curl:Could not connect", 0) == "curl:Could not connect");
     }
 }
+
+TEST_CASE("Print host error code is read from a JSON reply", "[PrintHost]")
+{
+    CHECK(PrintHost::get_err_code_from_body(R"({"err":0})") == 0);
+    CHECK(PrintHost::get_err_code_from_body(R"({"err":2})") == 2);
+    CHECK(PrintHost::get_err_code_from_body(R"({"status":"ok"})") == 0);
+}
+
+TEST_CASE("Print host error code reports a reply that is not JSON as an error", "[PrintHost]")
+{
+    const std::string body = GENERATE(from_range(non_json_replies));
+    int err = 0;
+    REQUIRE_NOTHROW(err = PrintHost::get_err_code_from_body(body));
+    CHECK(err != 0);
+}
+
+TEST_CASE("Print host error code tolerates a wrongly typed err field", "[PrintHost]")
+{
+    const std::string body = GENERATE(as<std::string>{}, R"({"err":"busy"})", R"({"err":{"code":1}})", R"([1,2])");
+    CHECK_NOTHROW(PrintHost::get_err_code_from_body(body));
+}
+
+TEST_CASE("Flashforge material slots are read from a well-formed reply", "[PrintHost][Flashforge]")
+{
+    const std::string body = R"({"code":0,"detail":{"hasMatlStation":true,"matlStationInfo":{"slotCnt":2,"slotInfos":[
+        {"slotId":1,"hasFilament":true,"materialName":"PLA","materialColor":"#FFFFFF"},
+        {"slotId":2,"hasFilament":false,"materialName":"","materialColor":""}]}}})";
+
+    std::vector<FlashforgeMaterialSlot> slots;
+    bool supports_station = false;
+    REQUIRE(Flashforge::parse_material_slots(body, slots, &supports_station));
+    CHECK(supports_station);
+    REQUIRE(slots.size() == 2);
+    CHECK(slots[0].slot_id == 1);
+    CHECK(slots[0].has_filament);
+    CHECK(slots[0].material_name == "PLA");
+    CHECK(slots[0].material_color == "#FFFFFF");
+    CHECK(slots[1].slot_id == 2);
+    CHECK_FALSE(slots[1].has_filament);
+}
+
+TEST_CASE("Flashforge material slots accept numbers as strings and flags as numbers", "[PrintHost][Flashforge]")
+{
+    const std::string body = R"({"detail":{"matlStationInfo":{"slotInfos":[
+        {"slotId":"3","hasFilament":1,"materialName":null,"materialColor":7}]}}})";
+
+    std::vector<FlashforgeMaterialSlot> slots;
+    REQUIRE_NOTHROW(Flashforge::parse_material_slots(body, slots, nullptr));
+    REQUIRE(slots.size() == 1);
+    CHECK(slots[0].slot_id == 3);
+    CHECK(slots[0].has_filament);
+    CHECK(slots[0].material_name.empty());
+    CHECK(slots[0].material_color.empty());
+}
+
+TEST_CASE("Flashforge material slots skip entries that are not objects", "[PrintHost][Flashforge]")
+{
+    const std::string body = R"({"detail":{"matlStationInfo":{"slotInfos":[5,"slot",null,[],
+        {"slotId":4,"hasFilament":true,"materialName":"PETG"}]}}})";
+
+    std::vector<FlashforgeMaterialSlot> slots;
+    REQUIRE_NOTHROW(Flashforge::parse_material_slots(body, slots, nullptr));
+    REQUIRE(slots.size() == 1);
+    CHECK(slots[0].slot_id == 4);
+    CHECK(slots[0].material_name == "PETG");
+}
+
+TEST_CASE("Flashforge material slots tolerate slot info that is not a list", "[PrintHost][Flashforge]")
+{
+    const std::string body = GENERATE(as<std::string>{},
+                                      R"({"detail":{"matlStationInfo":{"slotInfos":5}}})",
+                                      R"({"detail":{"matlStationInfo":{"slotInfos":"none"}}})",
+                                      R"({"detail":{"matlStationInfo":7}})",
+                                      R"({"detail":"offline"})");
+
+    std::vector<FlashforgeMaterialSlot> slots;
+    bool ok = false;
+    REQUIRE_NOTHROW(ok = Flashforge::parse_material_slots(body, slots, nullptr));
+    CHECK(ok);
+    CHECK(slots.empty());
+}
+
+TEST_CASE("Flashforge material slots reject a reply that is not JSON", "[PrintHost][Flashforge]")
+{
+    const std::string body = GENERATE(from_range(non_json_replies));
+    std::vector<FlashforgeMaterialSlot> slots;
+    bool ok = true;
+    REQUIRE_NOTHROW(ok = Flashforge::parse_material_slots(body, slots, nullptr));
+    CHECK_FALSE(ok);
+    CHECK(slots.empty());
+}

tests/slic3rutils/test_user_manager.cpp

@@ -0,0 +1,23 @@
+#include <catch2/catch_all.hpp>
+
+#include <string>
+
+#include "slic3r/GUI/UserManager.hpp"
+
+using namespace Slic3r;
+
+TEST_CASE("User message that is not JSON is rejected without throwing", "[UserManager]")
+{
+    const std::string payload = GENERATE(as<std::string>{}, "not json", "", "<html></html>", "{\"bind\":");
+    UserManager manager;
+    int result = 0;
+    REQUIRE_NOTHROW(result = manager.parse_json(payload));
+    CHECK(result == -1);
+}
+
+TEST_CASE("User message without a successful bind is ignored", "[UserManager]")
+{
+    const std::string payload = GENERATE(as<std::string>{}, "{}", R"({"bind":{"command":"unbind"}})", R"({"bind":"bind"})", "[1]");
+    UserManager manager;
+    CHECK(manager.parse_json(payload) == -1);
+}