fix(ue58): use versioned material sampler API

CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Fixed
+
+- **Material sampler discovery now uses the supported API on each engine version.** The material and generic-asset index paths share one compatibility boundary that calls `UMaterialExpressionTextureBase` on UE 5.7 and `MaterialExpressionUtils` on UE 5.8+, removing both sampler deprecation warnings without duplicating version branches.
+
 ## [0.22.0] - 2026-08-01
 
 ### Internal

Docs/specs/SPEC_MonolithCore.md

@@ -34,6 +34,7 @@
 
 | Symbol | Header | Responsibility |
 |--------|--------|---------------|
+| `MonolithMaterialSamplerCompat::GetSamplerTypeForTexture` | `MonolithMaterialSamplerCompat.h` (header-only inline) | Single UE 5.7/5.8 compatibility boundary for recommended material sampler selection. UE 5.7 routes to `UMaterialExpressionTextureBase`; UE 5.8+ routes to `MaterialExpressionUtils`, so consumers never call a deprecated engine API directly. |
 | `MonolithPinTypeGrammar::{TryParsePinType, ParsePinTypeFromString, PinTypeToString, ContainerPrefix, ResolveEnumByNameOrPath}` | `MonolithPinTypeGrammar.h` (header-only inline) | The single implementation of the MCP-friendly pin-type token grammar and its inverse — `bool` / `int` / `struct:Vector` / `enum:ESlateVisibility` / `array:object:StaticMesh` / `map:string:int` and so on. It previously existed twice (MonolithBlueprint + MonolithUI) and the copies drifted, which is what shipped enum widget variables that compiled to `int` (issue #115). `TryParsePinType` is the preferred entry point: it fails **by token** — an `object:` / `class:` / `struct:` / `enum:` / `softobject:` / `softclass:` sub-object that does not resolve, an unknown base token, or a bad container value type is a hard `false` with a caller-facing reason, and `Out` is left untouched. `ParsePinTypeFromString` keeps the historical best-effort shape (bool fallback, null sub-object) for un-migrated call sites. **Linkage invariant:** MonolithCore does not link `BlueprintGraph`, so this header is inline-only and must NEVER be included from a MonolithCore `.cpp` (or a MonolithCore test) — the `UEdGraphSchema_K2::PC_*` constants are dllimport'd from `BlueprintGraph` and referencing them from a MonolithCore translation unit is an LNK2019. Same pattern, and same reason, as `MonolithPropertyAccessReader.h` and `MonolithAnimNodeBindingReader.h`. The modules that do link `BlueprintGraph` and may include it from a `.cpp`: MonolithAI, MonolithAnimation, MonolithBlueprint, MonolithComboGraph, MonolithGAS, MonolithIndex, MonolithLevelSequence, MonolithLogicDriver, MonolithUI. |
 | `MonolithCore::ValidatePackagePath(const FString&)` | `MonolithPackagePathValidator.h` (inline) | Wraps `FPackageName::IsValidLongPackageName` with an empty-string-on-success / error-msg-on-failure contract. Rejects empty input, double-slash (`//Game/...`), missing `/Game/` root, trailing slash, illegal chars. Added `dv.367` after a fatal `UObjectGlobals.cpp:1012` ensure from a malformed `//Game/...` JSON payload reaching `CreatePackage`. Routing is incremental and module-keyed. Current owners: MonolithUI (`HandleCreateWidgetBlueprint`, the original crash site), MonolithAI (`MonolithAIInternal::GetOrCreatePackage`), MonolithGAS (`MonolithGASInternal::GetOrCreatePackage`); MonolithBlueprint, MonolithMaterial and MonolithNiagara are being wired now. Grep the Source tree for `ValidatePackagePath` for the current owner list rather than trusting a count here. |
 

Docs/specs/SPEC_MonolithIndex.md

@@ -27,7 +27,7 @@
 | `FGameplayTagIndexer` | GameplayTag containers — tag hierarchies and references |
 | `FConfigIndexer` | Config/INI files — sections, keys, values across config hierarchy |
 | `FCppIndexer` | C++ source files — classes, functions, includes (project-level source) |
-| `FGenericAssetIndexer` | StaticMesh, SkeletalMesh, Texture2D, SoundWave, etc. — metadata nodes |
+| `FGenericAssetIndexer` | StaticMesh, SkeletalMesh, Texture2D, SoundWave, etc. — metadata nodes. Texture `recommended_sampler_type` uses the shared `MonolithMaterialSamplerCompat` UE 5.7/5.8 boundary. |
 | `FDependencyIndexer` | Hard + Soft package dependencies (runs after all other indexers) |
 | `FMonolithIndexNotification` | Slate notification bar with throbber + percentage |
 

Docs/specs/SPEC_MonolithMaterial.md

@@ -15,7 +15,7 @@
 | Class | Responsibility |
 |-------|---------------|
 | `FMonolithMaterialModule` | Registers 63 material actions |
-| `FMonolithMaterialActions` | Static handlers + helpers for loading materials and serializing expressions |
+| `FMonolithMaterialActions` | Static handlers + helpers for loading materials and serializing expressions. Texture metadata routes sampler recommendation through the shared `MonolithMaterialSamplerCompat` UE 5.7/5.8 boundary. |
 
 ### Actions (63 — namespace: "material")
 

Docs/testing/2026-08-04-ue58-material-sampler-api.md

@@ -0,0 +1,37 @@
+# UE 5.8 Material Sampler API Verification
+
+**Date:** 2026-08-04
+**Scope:** `MonolithCore`, `MonolithIndex`, and `MonolithMaterial`
+**Related:** issue #121
+
+---
+
+## 1. Regression
+
+UE 5.8 deprecates `UMaterialExpressionTextureBase::GetSamplerTypeForTexture` in favor of `MaterialExpressionUtils::GetSamplerTypeForTexture`. UE 5.7 does not expose the replacement header, so an unconditional migration would break the supported compile floor. The deprecated call existed in both texture metadata consumers.
+
+## 2. Compatibility contract
+
+| Engine | Routed API |
+|---|---|
+| UE 5.7 | `UMaterialExpressionTextureBase::GetSamplerTypeForTexture` |
+| UE 5.8+ | `MaterialExpressionUtils::GetSamplerTypeForTexture` |
+
+Both consumers call `MonolithMaterialSamplerCompat::GetSamplerTypeForTexture`; the engine-version boundary is defined once in `Source/MonolithCore/Public/MonolithMaterialSamplerCompat.h`.
+
+## 3. Verification
+
+| Gate | Expected result | Result |
+|---|---|---|
+| Repository diff audit | One compatibility boundary and two migrated consumers | Pass — `git diff --check` returned no errors |
+| UE 5.7 plugin package build | Editor plugin compiles with the legacy API path | Pass — 434/434 actions, UAT exit 0 |
+| UE 5.8 plugin package build | Editor plugin compiles without either sampler deprecation warning | Pass — 434/434 actions, UAT exit 0, zero matching sampler C4996 warnings |
+
+Both builds compiled `GenericAssetIndexer.cpp` and `MonolithMaterialActions.cpp` as individual actions. Engine roots were resolved from validation-host `.uproject` `EngineAssociation` values through `Build/BatchFiles/Script/ResolveUnrealEngine.ps1`. UAT logs were redirected to external evidence paths:
+
+- `D:\P4\MonolithValidation20260804\02-ue58-material-sampler\Logs\UE57`
+- `D:\P4\MonolithValidation20260804\02-ue58-material-sampler\Logs\UE58`
+
+The authoritative command shape was `RunUAT BuildPlugin -NoTargetPlatforms -Rocket`. An earlier UE 5.7 run also completed all 434 compile actions, but its final UAT log flush failed because the system drive was full; the redirected-log exit-0 run above supersedes it.
+
+Issue #121 contains other engine deprecations that are intentionally outside this single-concern change.

Source/MonolithCore/Public/MonolithMaterialSamplerCompat.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "Runtime/Launch/Resources/Version.h"
+
+#if ENGINE_MAJOR_VERSION == 5 && ENGINE_MINOR_VERSION >= 8
+#include "Materials/MaterialExpressionUtils.h"
+#else
+#include "Materials/MaterialExpressionTextureBase.h"
+#endif
+
+class UTexture;
+
+namespace MonolithMaterialSamplerCompat
+{
+#if WITH_EDITOR
+/**
+ * Return Unreal's recommended sampler type without exposing engine-version API
+ * drift to each material or index consumer.
+ */
+FORCEINLINE EMaterialSamplerType GetSamplerTypeForTexture(
+	const UTexture* Texture,
+	bool bForceNoVirtualTexture = false)
+{
+#if ENGINE_MAJOR_VERSION == 5 && ENGINE_MINOR_VERSION >= 8
+	return MaterialExpressionUtils::GetSamplerTypeForTexture(Texture, bForceNoVirtualTexture);
+#else
+	return UMaterialExpressionTextureBase::GetSamplerTypeForTexture(Texture, bForceNoVirtualTexture);
+#endif
+}
+#endif
+}

Source/MonolithIndex/Private/Indexers/GenericAssetIndexer.cpp

@@ -1,8 +1,8 @@
 #include "Indexers/GenericAssetIndexer.h"
+#include "MonolithMaterialSamplerCompat.h"
 #include "Engine/StaticMesh.h"
 #include "Engine/SkeletalMesh.h"
 #include "Engine/Texture2D.h"
-#include "Materials/MaterialExpressionTextureBase.h"
 #include "Sound/SoundWave.h"
 #include "Sound/SoundCue.h"
 #include "PhysicsEngine/PhysicsAsset.h"
@@ -79,7 +79,7 @@ bool FGenericAssetIndexer::IndexAsset(const FAssetData& AssetData, UObject* Load
 		Props->SetBoolField(TEXT("compression_no_alpha"), Tex->CompressionNoAlpha != 0);
 #endif
 		// Recommended sampler type for material use
-		EMaterialSamplerType SamplerType = UMaterialExpressionTextureBase::GetSamplerTypeForTexture(Tex);
+		const EMaterialSamplerType SamplerType = MonolithMaterialSamplerCompat::GetSamplerTypeForTexture(Tex);
 		UEnum* SamplerEnum = StaticEnum<EMaterialSamplerType>();
 		if (SamplerEnum)
 		{

Source/MonolithMaterial/Private/MonolithMaterialActions.cpp

@@ -1,4 +1,5 @@
 #include "MonolithMaterialActions.h"
+#include "MonolithMaterialSamplerCompat.h"
 #include "MonolithToolRegistry.h"
 #include "MonolithParamSchema.h"
 #include "MonolithPackagePathValidator.h"
@@ -9344,7 +9345,7 @@ static void PopulateTextureMetadata(UTexture* Tex, const TSharedPtr<FJsonObject>
 #endif
 
 	// Recommended sampler type for material usage
-	EMaterialSamplerType SamplerType = UMaterialExpressionTextureBase::GetSamplerTypeForTexture(Tex);
+	const EMaterialSamplerType SamplerType = MonolithMaterialSamplerCompat::GetSamplerTypeForTexture(Tex);
 	UEnum* SamplerEnum = StaticEnum<EMaterialSamplerType>();
 	if (SamplerEnum)
 	{