Publish 3MF: import-side hardening and test coverage

Validate mixed-filament definitions during the published material pass: definitions whose components reference slots that do not exist or hold other mixed filaments, or that carry fewer than two components, are reported through the shared skipped_keys channel instead of shipping a mix the GUI integrity check would only flag later.

Fix the slot-limit exhaustion report being silently dropped: it wrote to published_config->skipped_keys, which the pass's final move-assignment from the local vector clobbers. All rejections now go through the local.

Remove the unreachable persist branch from add_detached_preset: no caller passes save_to_project=false, so the parameter is gone and the copy is always project-embedded.

Tests: cover the exhaustion path, the new definition validation, the identity-tier matching matrix (including substitute reporting), the structural-key denylist, whole-vector size-mismatch skips, relocation payload degradation, the "(Published 2)" uniquify chain, mixed blend colours staying out of shared preset configs, and duplicate-slot last-wins. Also fix the legacy-3mf scenario passing vacuously behind an if-guarded assertion. All existing published/3mf tests pass unchanged.

src/libslic3r/Preset.cpp

@@ -3064,14 +3064,14 @@ void PresetCollection::save_current_preset(const std::string &new_name, bool det
 // diff against a parent; the caller decides whether to select it.
 // The published entry's filament_id is forwarded so user bases keep their stable
 // material grouping (get_filament_presets() groups user bases by filament_id).
-// save_to_project=true (the Full Publish default) creates a project-embedded preset:
-// it lives inside the loaded project only (serialized into the saved .3mf, restored by
-// load_project_embedded_presets) and never touches the user's library directory;
-// Preset::save() early-returns for embedded presets, so persistence is skipped here too.
+// The copy is a project-embedded preset: it lives inside the loaded project only
+// (serialized into the saved .3mf, restored by load_project_embedded_presets) and
+// never touches the user's library directory; Preset::save() early-returns for
+// embedded presets, so persistence is skipped here too.
 // Returns the final (uniquified) name; on collision "<base>" -> "<base> (Published)" ->
 // "<base> (Published 2)" ...
 std::string PresetCollection::add_detached_preset(const std::string &name_base, DynamicPrintConfig config,
-                                                  const std::string &filament_id, bool save_to_project)
+                                                  const std::string &filament_id)
 {
     if (name_base.empty())
         return std::string();
@@ -3111,7 +3111,7 @@ std::string PresetCollection::add_detached_preset(const std::string &name_base,
     preset.bundle_id.clear();
     preset.file                = this->path_for_preset(preset);
     preset.is_visible          = true;
-    preset.is_project_embedded = save_to_project;
+    preset.is_project_embedded = true;
     if (m_type == Preset::TYPE_PRINT)
         preset.config.option<ConfigOptionString>("print_settings_id", true)->value = final_name;
     else if (m_type == Preset::TYPE_FILAMENT)
@@ -3120,14 +3120,6 @@ std::string PresetCollection::add_detached_preset(const std::string &name_base,
         preset.config.option<ConfigOptionString>("printer_settings_id", true)->value = final_name;
     unlock();
 
-    if (!save_to_project) {
-        // Persist the full resolved config (no parent). Project-embedded presets are
-        // serialized into the .3mf instead; Preset::save() would early-return anyway.
-        // find by final_name — m_presets may have reallocated, so don't keep a raw ref.
-        auto persist_it = this->find_preset_internal(final_name);
-        if (persist_it != m_presets.end() && persist_it->name == final_name)
-            persist_it->save(nullptr);
-    }
     return final_name;
 }
 

src/libslic3r/Preset.hpp

@@ -639,16 +639,14 @@ public:
     // preset's stable material grouping (get_filament_presets groups user bases by
     // filament_id); the published entry's filament_id is forwarded so the copy keeps
     // the author's grouping.
-    // With save_to_project=true (default) the copy is a project-embedded preset
-    // ("Preset Inside Project"): it lives inside the loaded project only, is serialized
-    // into the saved .3mf via get_current_project_embedded_presets(), and is never
-    // written to the user's library directory. With false it persists as a normal
-    // user preset file.
+    // The copy is a project-embedded preset ("Preset Inside Project"): it lives inside
+    // the loaded project only, is serialized into the saved .3mf via
+    // get_current_project_embedded_presets(), and is never written to the user's
+    // library directory.
     // Returns the final (uniquified) name; on collision the suffix rule is:
     // "<base>" -> "<base> (Published)" -> "<base> (Published 2)" ...
     std::string     add_detached_preset(const std::string &name_base, DynamicPrintConfig config,
-                                        const std::string &filament_id = std::string(),
-                                        bool save_to_project = true);
+                                        const std::string &filament_id = std::string());
 
     // Delete the current preset, activate the first visible preset.
     // returns true if the preset was deleted successfully.

src/libslic3r/PresetBundle.cpp

@@ -5466,8 +5466,10 @@ void PresetBundle::load_config_file_config(const std::string& name_or_path,
                     const std::string material_label = !entry.filament_id.empty()           ? entry.filament_id :
                                                        !entry.publish_type_value.empty()    ? entry.publish_type_value :
                                                                                                entry.filament_type;
-                    published_config->skipped_keys.emplace_back("material:" + material_label +
-                                                                " (mixed filament definition: filament slot limit reached)");
+                    // The local skipped_keys is published wholesale at the end of the pass;
+                    // writing published_config->skipped_keys here would be clobbered by it.
+                    skipped_keys.emplace_back("material:" + material_label +
+                                              " (mixed filament definition: filament slot limit reached)");
                     BOOST_LOG_TRIVIAL(warning) << __FUNCTION__ << ": published 3MF mixed filament from slot " << entry.slot
                                                << " could not be placed: all " << next_free_slot << " slots exhausted";
                     entry_it = published_config->material_keys.erase(entry_it);
@@ -5880,6 +5882,19 @@ void PresetBundle::load_config_file_config(const std::string& name_or_path,
                 // slots wrote to it; that compound case is not chased.)
                 const bool edited_survives_load = this->filament_presets.empty() ||
                                                   this->filament_presets.front() == this->filaments.get_edited_preset().name;
+                // Final layout for mix-definition validation: every slot that will hold a
+                // mixed definition once this load completes - the receiver's own virtual
+                // slots plus each published mixed entry's final (possibly relocated) slot.
+                // Mix components are 1-based slot numbers, so a component is valid only
+                // when the slot it names exists and does not itself hold a mixed filament.
+                std::set<int> mixed_final_slots;
+                for (const PublishedMaterialEntry& mix_entry : published_config->material_keys)
+                    if (mix_entry.slot >= 0 && is_mixed_definition(mix_entry))
+                        mixed_final_slots.insert(mix_entry.slot);
+                for (size_t i = 0; i < this->filament_presets.size(); ++i)
+                    if (this->is_mixed_filament(i))
+                        mixed_final_slots.insert(int(i));
+                const size_t mixed_final_slot_count = this->filament_presets.size();
                 // Full Publish within-load dedup: identical Full materials (same setting_id
                 // + preset_name identity) share one created instance, so an author who
                 // pointed two slots at one preset yields one standalone copy here.
@@ -5900,6 +5915,40 @@ void PresetBundle::load_config_file_config(const std::string& name_or_path,
                                                                                                entry.publish_type_value) :
                                                            entry.filament_id;
 
+                    // Import-side validation of a mixed-filament definition: the publish
+                    // dialog cannot produce a definition whose components reference slots
+                    // that do not exist or hold other mixed filaments, so a broken one here
+                    // means the payload itself is broken (hand-crafted or corrupt file).
+                    // Report it through the same channel as every other rejected input and
+                    // skip the entry, instead of shipping a mix the GUI integrity check
+                    // (check_mixed_filament_integrity) would only flag later. A payload
+                    // that omits the mixed arrays entirely is not an error here: the key
+                    // routing below reports those per key as usual.
+                    if (is_mixed_definition(entry)) {
+                        std::string mix_error;
+                        if (const ConfigOptionStrings* comp_opt = config.opt<ConfigOptionStrings>("filament_mixed_components");
+                            comp_opt != nullptr && entry.slot < static_cast<int>(comp_opt->values.size())) {
+                            const std::vector<unsigned int> comps = parse_mixed_components(comp_opt->values[entry.slot]);
+                            if (comps.size() < 2)
+                                // An empty definition cell counts as broken too: applying it
+                                // would ship a mix the sidebar would only flag later.
+                                mix_error = "needs at least two components";
+                            else
+                                for (unsigned int comp : comps)
+                                    if (comp < 1 || size_t(comp) > mixed_final_slot_count ||
+                                        mixed_final_slots.count(int(comp) - 1) != 0) {
+                                        mix_error = "components reference missing slots";
+                                        break;
+                                    }
+                        }
+                        if (!mix_error.empty()) {
+                            skipped_keys.emplace_back("material:" + material_label + " (mixed filament definition: " + mix_error + ")");
+                            BOOST_LOG_TRIVIAL(warning) << __FUNCTION__ << ": published 3MF mixed filament from slot " << entry.slot
+                                                       << " rejected: " << mix_error;
+                            continue;
+                        }
+                    }
+
                     // Full Publish: always create a standalone detached copy (even on exact
                     // identity match) as a "Preset Inside Project" (project-embedded: lives
                     // in this project only, never written to the library), universally