Merge remote-tracking branch 'XRPLF/develop' into ximinez/emptydirectoryinvariant

* XRPLF/develop: (30 commits)
  chore: Pin Python packages for codegen using uv (7329)
  style: Use shfmt instead of bashate (7326)
  fix: Fix edge-case where vault-depositor may get stuck (7139)
  fix: Fix `VaultInvariant` and `VaultDeposit` precision bugs at IOU scale boundaries (7272)
  ci: Add clang to nix images (7308)
  fix: Include management-fee delta in doOverpayment assertion (7039)
  fix: Fix clang-tidy pre-commit hook to locate compile_commands.json from repo root (7325)
  fix: Use consistent scale for `debtTotal` (7093)
  fix: Skip deleted book directories and non-root modifications in `ValidBookDirectory` invariant (7312)
  fix: Address review feedback on FD/handle guarding (5823 follow-up) (7310)
  fix: Fix non-canonical MPT amount (7117)
  release: Bump version to 3.2.0-b7 (7316)
  fix: Check if the MPT first loss cover can be sent to the broker before deleting the broker (7125)
  fix: Fix RPM prerelease ordering and start xrpld on DEB install (7313)
  ci: Re-enable full nproc for Linux (7315)
  fix: Add assorted MPT/DEX fixes (7040)
  refactor: Remove dead `fetchBatch` code (7309)
  release: Bump version to 3.2.0-b6 (7311)
  chore: Revert graceful peer disconnection and follow-up fix (7296)
  fix: Fix IOU precision issues in LoanBrokerCover transactions (7274)
  ...

include/xrpl/ledger/helpers/NFTokenHelpers.h

@@ -20,6 +20,10 @@ removeTokenOffersWithLimit(
     Keylet const& directory,
     std::size_t maxDeletableOffers);
 
+/** Returns tesSUCCESS if NFToken has few enough offers that it can be burned */
+TER
+notTooManyOffers(ReadView const& view, uint256 const& nftokenID);
+
 /** Finds the specified token in the owner's token directory. */
 std::optional<STObject>
 findToken(ReadView const& view, AccountID const& owner, uint256 const& nftokenID);

include/xrpl/tx/invariants/InvariantCheck.h

@@ -373,6 +373,22 @@ public:
     finalize(STTx const&, TER const, XRPAmount const, ReadView const&, beast::Journal const&);
 };
 
+/**
+ * @brief Invariants: An account's directory should never be empty
+ *
+ */
+class NoEmptyDirectory
+{
+    bool bad_ = false;
+
+public:
+    void
+    visitEntry(bool, std::shared_ptr<SLE const> const&, std::shared_ptr<SLE const> const&);
+
+    bool
+    finalize(STTx const&, TER const, XRPAmount const, ReadView const&, beast::Journal const&);
+};
+
 /** Verify that MPT/XRP STAmounts are canonical in any ledger entries left after the
  * transaction applies.
  */
@@ -418,7 +434,8 @@ using InvariantChecks = std::tuple<
     ValidVault,
     ValidMPTPayment,
     ValidAmounts,
-    ValidMPTTransfer>;
+    ValidMPTTransfer,
+    NoEmptyDirectory>;
 
 /**
  * @brief get a tuple of all invariant checks

src/libxrpl/ledger/ApplyView.cpp

@@ -255,6 +255,7 @@ ApplyView::emptyDirDelete(Keylet const& directory)
 bool
 ApplyView::dirRemove(Keylet const& directory, std::uint64_t page, uint256 const& key, bool keepRoot)
 {
+    keepRoot = false;
     auto node = peek(keylet::page(directory, page));
 
     if (!node)

src/libxrpl/ledger/helpers/NFTokenHelpers.cpp

@@ -622,6 +622,33 @@ removeTokenOffersWithLimit(ApplyView& view, Keylet const& directory, std::size_t
     return deletedOffersCount;
 }
 
+TER
+notTooManyOffers(ReadView const& view, uint256 const& nftokenID)
+{
+    std::size_t totalOffers = 0;
+
+    {
+        Dir const buys(view, keylet::nftBuys(nftokenID));
+        for (auto iter = buys.begin(); iter != buys.end(); iter.next_page())
+        {
+            totalOffers += iter.page_size();
+            if (totalOffers > kMaxDeletableTokenOfferEntries)
+                return tefTOO_BIG;
+        }
+    }
+
+    {
+        Dir const sells(view, keylet::nftSells(nftokenID));
+        for (auto iter = sells.begin(); iter != sells.end(); iter.next_page())
+        {
+            totalOffers += iter.page_size();
+            if (totalOffers > kMaxDeletableTokenOfferEntries)
+                return tefTOO_BIG;
+        }
+    }
+    return tesSUCCESS;
+}
+
 bool
 deleteTokenOffer(ApplyView& view, std::shared_ptr<SLE> const& offer)
 {

src/libxrpl/tx/invariants/InvariantCheck.cpp

@@ -1080,6 +1080,46 @@ NoModifiedUnmodifiableFields::finalize(
     return true;
 }
 
+//------------------------------------------------------------------------------
+
+void
+NoEmptyDirectory::visitEntry(
+    bool isDelete,
+    std::shared_ptr<SLE const> const& before,
+    std::shared_ptr<SLE const> const& after)
+{
+    if (isDelete)
+        return;
+    if (before && before->getType() != ltDIR_NODE)
+        return;
+    if (after && after->getType() != ltDIR_NODE)
+        return;
+    if (!after->isFieldPresent(sfOwner))
+        // Not an account dir
+        return;
+
+    bad_ = after->at(sfIndexes).empty();
+}
+
+bool
+NoEmptyDirectory::finalize(
+    STTx const& tx,
+    TER const result,
+    XRPAmount const,
+    ReadView const& view,
+    beast::Journal const& j)
+{
+    if (bad_)
+    {
+        JLOG(j.fatal()) << "Invariant failed: empty owner directory.";
+        return false;
+    }
+
+    return true;
+}
+
+//------------------------------------------------------------------------------
+
 void
 ValidAmounts::visitEntry(
     bool isDelete,