Merge bitcoin/bitcoin#32596: wallet, rpc, doc: various legacy wallet removal cleanups in RPCs

e5cbea4 rpc: doc: remove redundant "descriptors" parameter in `createwallet` examples (Sebastian Falbesoner)
7a05f94 rpc: doc: drop descriptor wallet mentions in fast wallet rescan related RPCs (Sebastian Falbesoner)
db465a5 wallet, rpc: remove obsolete "keypoololdest" result field/code (Sebastian Falbesoner)

Pull request description:

  This PR contains a few smaller wallet RPC cleanups based on that we only ever operate on descriptor wallets now:
  * remove the now obsolete "keypoololdest" field from the `getwalletinfo` RPC and the corresponding CWallet/ScriptPubKeyMan methods
  * in RPCs where potential fast wallet rescan is documented, remove the "descriptor wallet" mentions (back then introduced in commit ca48a46, PR #25957)
  * for the `createwallet` RPC examples, remove the "descriptors" parameters that always have to be true now (proposed in bitcoin/bitcoin#31250 (comment); corresponds to 86de8c1, PR #32544 which did the same for functional tests)

ACKs for top commit:
  achow101:
    ACK e5cbea4
  1440000bytes:
    ACK bitcoin/bitcoin@e5cbea4
  rkrux:
    ACK e5cbea4

Tree-SHA512: d785f621af3f3987b258e5d7fb8309344fb13c2cf41855f8adf99ff89f581142db36e3ba59919d6abf82662caa3f7e4a2bd38eba1be9e23665e6a4a23ee52acd

Author: achow101

src/wallet/rpc/backup.cpp

@@ -611,8 +611,8 @@ RPCHelpMan restorewallet()
     return RPCHelpMan{
         "restorewallet",
         "Restores and loads a wallet from backup.\n"
-        "\nThe rescan is significantly faster if a descriptor wallet is restored"
-        "\nand block filters are available (using startup option \"-blockfilterindex=1\").\n",
+        "\nThe rescan is significantly faster if block filters are available"
+        "\n(using startup option \"-blockfilterindex=1\").\n",
         {
             {"wallet_name", RPCArg::Type::STR, RPCArg::Optional::NO, "The name that will be applied to the restored wallet"},
             {"backup_file", RPCArg::Type::STR, RPCArg::Optional::NO, "The backup file that will be used to restore the wallet."},

src/wallet/rpc/transactions.cpp

@@ -857,8 +857,8 @@ RPCHelpMan rescanblockchain()
         "rescanblockchain",
         "Rescan the local blockchain for wallet related transactions.\n"
                 "Note: Use \"getwalletinfo\" to query the scanning progress.\n"
-                "The rescan is significantly faster when used on a descriptor wallet\n"
-                "and block filters are available (using startup option \"-blockfilterindex=1\").\n",
+                "The rescan is significantly faster if block filters are available\n"
+                "(using startup option \"-blockfilterindex=1\").\n",
                 {
                     {"start_height", RPCArg::Type::NUM, RPCArg::Default{0}, "block height where the rescan should start"},
                     {"stop_height", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "the last block height that should be scanned. If none is provided it will rescan up to the tip at return time of this call."},

src/wallet/rpc/wallet.cpp

@@ -46,7 +46,6 @@ static RPCHelpMan getwalletinfo()
                         {RPCResult::Type::STR_AMOUNT, "unconfirmed_balance", "DEPRECATED. Identical to getbalances().mine.untrusted_pending"},
                         {RPCResult::Type::STR_AMOUNT, "immature_balance", "DEPRECATED. Identical to getbalances().mine.immature"},
                         {RPCResult::Type::NUM, "txcount", "the total number of transactions in the wallet"},
-                        {RPCResult::Type::NUM_TIME, "keypoololdest", /*optional=*/true, "the " + UNIX_EPOCH_TIME + " of the oldest pre-generated key in the key pool. Legacy wallets only."},
                         {RPCResult::Type::NUM, "keypoolsize", "how many new keys are pre-generated (only counts external keys)"},
                         {RPCResult::Type::NUM, "keypoolsize_hd_internal", /*optional=*/true, "how many new keys are pre-generated for internal use (used for change outputs, only appears if the wallet is using this feature, otherwise external keys are used)"},
                         {RPCResult::Type::NUM_TIME, "unlocked_until", /*optional=*/true, "the " + UNIX_EPOCH_TIME + " until which the wallet is unlocked for transfers, or 0 if the wallet is locked (only present for passphrase-encrypted wallets)"},
@@ -91,10 +90,6 @@ static RPCHelpMan getwalletinfo()
     obj.pushKV("unconfirmed_balance", ValueFromAmount(bal.m_mine_untrusted_pending));
     obj.pushKV("immature_balance", ValueFromAmount(bal.m_mine_immature));
     obj.pushKV("txcount",       (int)pwallet->mapWallet.size());
-    const auto kp_oldest = pwallet->GetOldestKeyPoolTime();
-    if (kp_oldest.has_value()) {
-        obj.pushKV("keypoololdest", kp_oldest.value());
-    }
     obj.pushKV("keypoolsize", (int64_t)kpExternalSize);
 
     if (pwallet->CanSupportFeature(FEATURE_HD_SPLIT)) {
@@ -356,8 +351,8 @@ static RPCHelpMan createwallet()
         RPCExamples{
             HelpExampleCli("createwallet", "\"testwallet\"")
             + HelpExampleRpc("createwallet", "\"testwallet\"")
-            + HelpExampleCliNamed("createwallet", {{"wallet_name", "descriptors"}, {"avoid_reuse", true}, {"descriptors", true}, {"load_on_startup", true}})
-            + HelpExampleRpcNamed("createwallet", {{"wallet_name", "descriptors"}, {"avoid_reuse", true}, {"descriptors", true}, {"load_on_startup", true}})
+            + HelpExampleCliNamed("createwallet", {{"wallet_name", "descriptors"}, {"avoid_reuse", true}, {"load_on_startup", true}})
+            + HelpExampleRpcNamed("createwallet", {{"wallet_name", "descriptors"}, {"avoid_reuse", true}, {"load_on_startup", true}})
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {

src/wallet/scriptpubkeyman.cpp

@@ -1189,13 +1189,6 @@ bool DescriptorScriptPubKeyMan::HaveCryptedKeys() const
     return !m_map_crypted_keys.empty();
 }
 
-std::optional<int64_t> DescriptorScriptPubKeyMan::GetOldestKeyPoolTime() const
-{
-    // This is only used for getwalletinfo output and isn't relevant to descriptor wallets.
-    return std::nullopt;
-}
-
-
 unsigned int DescriptorScriptPubKeyMan::GetKeyPoolSize() const
 {
     LOCK(cs_desc_man);

src/wallet/scriptpubkeyman.h

@@ -133,8 +133,6 @@ class ScriptPubKeyMan
     //! The action to do when the DB needs rewrite
     virtual void RewriteDB() {}
 
-    virtual std::optional<int64_t> GetOldestKeyPoolTime() const { return GetTime(); }
-
     virtual unsigned int GetKeyPoolSize() const { return 0; }
 
     virtual int64_t GetTimeFirstKey() const { return 0; }
@@ -364,7 +362,6 @@ class DescriptorScriptPubKeyMan : public ScriptPubKeyMan
     std::optional<CKey> GetKey(const CKeyID& keyid) const EXCLUSIVE_LOCKS_REQUIRED(cs_desc_man);
     bool HaveCryptedKeys() const override;
 
-    std::optional<int64_t> GetOldestKeyPoolTime() const override;
     unsigned int GetKeyPoolSize() const override;
 
     int64_t GetTimeFirstKey() const override;

src/wallet/wallet.cpp

@@ -2506,20 +2506,6 @@ util::Result<CTxDestination> CWallet::GetNewChangeDestination(const OutputType t
     return op_dest;
 }
 
-std::optional<int64_t> CWallet::GetOldestKeyPoolTime() const
-{
-    LOCK(cs_wallet);
-    if (m_spk_managers.empty()) {
-        return std::nullopt;
-    }
-
-    std::optional<int64_t> oldest_key{std::numeric_limits<int64_t>::max()};
-    for (const auto& spk_man_pair : m_spk_managers) {
-        oldest_key = std::min(oldest_key, spk_man_pair.second->GetOldestKeyPoolTime());
-    }
-    return oldest_key;
-}
-
 void CWallet::MarkDestinationsDirty(const std::set<CTxDestination>& destinations) {
     for (auto& entry : mapWallet) {
         CWalletTx& wtx = entry.second;

src/wallet/wallet.h

@@ -733,8 +733,6 @@ class CWallet final : public WalletStorage, public interfaces::Chain::Notificati
     size_t KeypoolCountExternalKeys() const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     bool TopUpKeyPool(unsigned int kpSize = 0);
 
-    std::optional<int64_t> GetOldestKeyPoolTime() const;
-
     // Filter struct for 'ListAddrBookAddresses'
     struct AddrBookFilter {
         // Fetch addresses with the provided label