Added sanity check baseline made by claude.

Also changed the location to a panel in VIEW_3D instead of menu.

checks/general/nodes.py

@@ -0,0 +1,90 @@
+import bpy
+
+from ...core import Check, Issue, Severity, contexts, is_local
+
+# Node types that make a tree produce something.
+_OUTPUT_TYPES = {
+    "OUTPUT_MATERIAL", "OUTPUT_WORLD", "OUTPUT_LIGHT", "OUTPUT_AOV", "OUTPUT_LINESTYLE",
+    "COMPOSITE", "OUTPUT_FILE", "VIEWER",
+}
+# Node types never reported as unused.
+_IGNORED_TYPES = {"FRAME", "GROUP_INPUT"}
+
+
+def unused_nodes(tree):
+    """Nodes that do not contribute to any output of ``tree``.
+
+    Returns None when the tree has no output at all (nothing to compare with).
+    """
+    roots = [
+        node for node in tree.nodes
+        if node.type in _OUTPUT_TYPES
+        or (node.type == "GROUP_OUTPUT" and getattr(node, "is_active_output", True))
+    ]
+    if not roots:
+        return None
+
+    upstream = {}
+    for link in tree.links:
+        upstream.setdefault(link.to_node.name, []).append(link.from_node)
+
+    used = set()
+    stack = list(roots)
+    while stack:
+        node = stack.pop()
+        if node.name in used:
+            continue
+        used.add(node.name)
+        stack.extend(upstream.get(node.name, ()))
+
+    return [node for node in tree.nodes if node.name not in used and node.type not in _IGNORED_TYPES]
+
+
+def _node_trees():
+    """(owner datablock, node tree) of every local node tree in use."""
+    for material in bpy.data.materials:
+        if is_local(material) and material.users and material.node_tree:
+            yield material, material.node_tree
+    for world in bpy.data.worlds:
+        if is_local(world) and world.users and world.node_tree:
+            yield world, world.node_tree
+    for group in bpy.data.node_groups:
+        if is_local(group) and group.users:
+            yield group, group
+
+
+def _tree_of(owner):
+    return owner if isinstance(owner, bpy.types.NodeTree) else owner.node_tree
+
+
+class UnusedNodesCheck(Check):
+    id = "unused_nodes"
+    label = "Unused nodes"
+    description = "Material, world and node group trees contain no node disconnected from the output."
+    category = "Shading"
+    contexts = contexts.ASSET
+    severity = Severity.WARNING
+    fix_description = "Delete the unused nodes"
+
+    def run(self, ctx):
+        for owner, tree in _node_trees():
+            nodes = unused_nodes(tree)
+            if nodes:
+                names = [node.name for node in nodes]
+                shown = ", ".join(names[:5]) + (" ..." if len(names) > 5 else "")
+                yield Issue.for_id(
+                    f"{owner.name}: {len(names)} unused node(s): {shown}",
+                    owner,
+                    data={"nodes": names},
+                )
+
+    def fix(self, ctx, issues):
+        for issue in issues:
+            owner = issue.get_id()
+            if owner is None:
+                continue
+            tree = _tree_of(owner)
+            for name in issue.data["nodes"]:
+                node = tree.nodes.get(name)
+                if node is not None:
+                    tree.nodes.remove(node)