Fix horizontal rule can() check always returning true (#6492)

* fixed the horizontal rule command always returning true, even if it's not insertable

* added changeset

* move canInsertNode util to core

* added changeset

* simplify matchType call

* fix import

* adjust import and export paths

Author: bdbch

.changeset/modern-kangaroos-teach.md

@@ -0,0 +1,5 @@
+---
+'@tiptap/extension-horizontal-rule': patch
+---
+
+Fixed a bug that caused the horizontal rule's `setHorizontalRule` command to always return true when checked via `can()`

.changeset/silver-roses-joke.md

@@ -0,0 +1,5 @@
+---
+'@tiptap/core': patch
+---
+
+Added new `canInsertNode` utility that checks if a node can be inserted into a specific position

packages/core/src/utilities/canInsertNode.ts

@@ -0,0 +1,30 @@
+import type { NodeType } from '@tiptap/pm/model'
+import { type EditorState, NodeSelection } from '@tiptap/pm/state'
+
+export function canInsertNode(state: EditorState, nodeType: NodeType): boolean {
+  const { selection } = state
+  const { $from } = selection
+
+  // Special handling for NodeSelection
+  if (selection instanceof NodeSelection) {
+    const index = $from.index()
+    const parent = $from.parent
+
+    // Can we replace the selected node with the horizontal rule?
+    return parent.canReplaceWith(index, index + 1, nodeType)
+  }
+
+  // Default: check if we can insert at the current position
+  let depth = $from.depth
+
+  while (depth >= 0) {
+    const index = $from.index(depth)
+    const parent = $from.node(depth)
+    const match = parent.contentMatchAt(index)
+    if (match.matchType(nodeType)) {
+      return true
+    }
+    depth -= 1
+  }
+  return false
+}

packages/core/src/utilities/index.ts

@@ -1,4 +1,5 @@
 export * from './callOrReturn.js'
+export * from './canInsertNode.js'
 export * from './createStyleTag.js'
 export * from './deleteProps.js'
 export * from './elementFromString.js'

packages/extension-horizontal-rule/src/horizontal-rule.ts

@@ -1,4 +1,4 @@
-import { isNodeSelection, mergeAttributes, Node, nodeInputRule } from '@tiptap/core'
+import { canInsertNode, isNodeSelection, mergeAttributes, Node, nodeInputRule } from '@tiptap/core'
 import { NodeSelection, TextSelection } from '@tiptap/pm/state'
 
 export interface HorizontalRuleOptions {
@@ -50,6 +50,11 @@ export const HorizontalRule = Node.create<HorizontalRuleOptions>({
       setHorizontalRule:
         () =>
         ({ chain, state }) => {
+          // Check if we can insert the node at the current selection
+          if (!canInsertNode(state, state.schema.nodes[this.name])) {
+            return false
+          }
+
           const { selection } = state
           const { $to: $originTo } = selection