wallet: Make -wallet setting not create wallets

This changes -wallet setting to only load existing wallets, not create new ones.

- Fixes settings.json corner cases reported by sjors & promag:
  https://github.com/bitcoin-core/gui/issues/95,
  https://github.com/bitcoin/bitcoin/pull/19754#issuecomment-685858578,
  https://github.com/bitcoin/bitcoin/pull/19754#issuecomment-685858578

- Prevents accidental creation of wallets reported most recently by jb55
  http://www.erisian.com.au/bitcoin-core-dev/log-2020-09-14.html#l-355

- Simplifies behavior after #15454. #15454 took the big step of disabling
  creation of the default wallet. This PR extends it to avoid creating other
  wallets as well. With this change, new wallets just aren't created on
  startup, instead of sometimes being created, sometimes not. #15454 release
  notes are updated here and are simpler.

This change should be targeted for 0.21.0. It's a bug fix and simplifies
behavior of the #15937 / #19754 / #15454 features added in 0.21.0.

2 files changed, 12 insertions, 3 deletions

diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 5d8c4fba29..8b2ef191fb 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -60,7 +60,7 @@ void WalletInit::AddWalletOptions(ArgsManager& argsman) const
     argsman.AddArg("-rescan", "Rescan the block chain for missing wallet transactions on startup", ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
     argsman.AddArg("-spendzeroconfchange", strprintf("Spend unconfirmed change when sending transactions (default: %u)", DEFAULT_SPEND_ZEROCONF_CHANGE), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
     argsman.AddArg("-txconfirmtarget=<n>", strprintf("If paytxfee is not set, include enough fee so transactions begin confirmation on average within n blocks (default: %u)", DEFAULT_TX_CONFIRM_TARGET), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
-    argsman.AddArg("-wallet=<path>", "Specify wallet database path. Can be specified multiple times to load multiple wallets. Path is interpreted relative to <walletdir> if it is not absolute, and will be created if it does not exist (as a directory containing a wallet.dat file and log files). For backwards compatibility this will also accept names of existing data files in <walletdir>.)", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::WALLET);
+    argsman.AddArg("-wallet=<path>", "Specify wallet path to load at startup. Can be used multiple times to load multiple wallets. Path is to a directory containing wallet data and log files. If the path is not absolute, it is interpreted relative to <walletdir>. This only loads existing wallets and does not create new ones. For backwards compatibility this also accepts names of existing top-level data files in <walletdir>.", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::WALLET);
     argsman.AddArg("-walletbroadcast",  strprintf("Make the wallet broadcast transactions (default: %u)", DEFAULT_WALLETBROADCAST), ArgsManager::ALLOW_ANY, OptionsCategory::WALLET);
     argsman.AddArg("-walletdir=<dir>", "Specify directory to hold wallets (default: <datadir>/wallets if it exists, otherwise <datadir>)", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::WALLET);
 #if HAVE_SYSTEM
diff --git a/src/wallet/load.cpp b/src/wallet/load.cpp
index 1b057000d2..1cdcb35fc7 100644
--- a/src/wallet/load.cpp
+++ b/src/wallet/load.cpp
@@ -71,11 +71,16 @@ bool VerifyWallets(interfaces::Chain& chain)
 
         DatabaseOptions options;
         DatabaseStatus status;
+        options.require_existing = true;
         options.verify = true;
         bilingual_str error_string;
         if (!MakeWalletDatabase(wallet_file, options, status, error_string)) {
-            chain.initError(error_string);
-            return false;
+            if (status == DatabaseStatus::FAILED_NOT_FOUND) {
+                chain.initWarning(Untranslated(strprintf("Skipping -wallet path that doesn't exist. %s\n", error_string.original)));
+            } else {
+                chain.initError(error_string);
+                return false;
+            }
         }
     }
 
@@ -88,10 +93,14 @@ bool LoadWallets(interfaces::Chain& chain)
         for (const std::string& name : gArgs.GetArgs("-wallet")) {
             DatabaseOptions options;
             DatabaseStatus status;
+            options.require_existing = true;
             options.verify = false; // No need to verify, assuming verified earlier in VerifyWallets()
             bilingual_str error;
             std::vector<bilingual_str> warnings;
             std::unique_ptr<WalletDatabase> database = MakeWalletDatabase(name, options, status, error);
+            if (!database && status == DatabaseStatus::FAILED_NOT_FOUND) {
+                continue;
+            }
             std::shared_ptr<CWallet> pwallet = database ? CWallet::Create(chain, name, std::move(database), options.create_flags, error, warnings) : nullptr;
             if (!warnings.empty()) chain.initWarning(Join(warnings, Untranslated("\n")));
             if (!pwallet) {