Deprecate old hash fields of `getblocktemplate`

doc/book/src/user/deprecation.md

@@ -37,6 +37,7 @@ the node, or if an `allowdeprecated=none` line is added to `zcash.conf`.
 
 | `feature`             | Deprecated | Feature details
 |-----------------------|------------|----------------
+| `gbt_oldhashes`       | 5.4.0      | The `finalsaplingroothash`, `lightclientroothash`, and `blockcommitmentshash` fields in the output of `getblocktemplate`, which are replaced by the `defaultroots` field.
 
 Stage 2
 -------

doc/release-notes.md

@@ -17,6 +17,15 @@ RPC Changes
 [Deprecations](https://zcash.github.io/zcash/user/deprecation.html)
 --------------
 
+The following features have been deprecated, but remain available by default.
+These features may be disabled by setting `-allowdeprecated=none`. 18 weeks
+after this release, these features will be disabled by default and the following
+flags to `-allowdeprecated` will be required to permit their continued use:
+
+- `gbt_oldhashes`: the `finalsaplingroothash`, `lightclientroothash`, and
+  `blockcommitmentshash` fields in the output of `getblocktemplate` have been
+  replaced by the `defaultroots` field.
+
 The following previously-deprecated features have been disabled by default, and
 will be removed in 18 weeks:
 

qa/rpc-tests/show_help.py

@@ -35,10 +35,10 @@ Options:
   -allowdeprecated=<feature>
        Explicitly allow the use of the specified deprecated feature. Multiple
        instances of this parameter are permitted; values for <feature> must be
-       selected from among {"none", "addrtype", "getnewaddress",
-       "getrawchangeaddress", "legacy_privacy", "wallettxvjoinsplit",
-       "z_getbalance", "z_getnewaddress", "z_gettotalbalance",
-       "z_listaddresses"}
+       selected from among {"none", "gbt_oldhashes", "addrtype",
+       "getnewaddress", "getrawchangeaddress", "legacy_privacy",
+       "wallettxvjoinsplit", "z_getbalance", "z_getnewaddress",
+       "z_gettotalbalance", "z_listaddresses"}
 
   -blocknotify=<cmd>
        Execute command when the best block changes (%s in cmd is replaced by

src/deprecation.cpp

@@ -12,6 +12,7 @@
 #include "chainparams.h"
 
 // Flags that enable deprecated functionality.
+bool fEnableGbtOldHashes = true;
 #ifdef ENABLE_WALLET
 bool fEnableGetNewAddress = true;
 bool fEnableGetRawChangeAddress = true;
@@ -91,6 +92,7 @@ std::optional<std::string> SetAllowedDeprecatedFeaturesFromCLIArgs() {
                 unrecMsg, GetAllowableDeprecatedFeatures());
     }
 
+    fEnableGbtOldHashes = allowdeprecated.count("gbt_oldhashes") > 0;
 #ifdef ENABLE_WALLET
     fEnableLegacyPrivacyStrategy = allowdeprecated.count("legacy_privacy") > 0;
     fEnableGetNewAddress = allowdeprecated.count("getnewaddress") > 0;

src/deprecation.h

@@ -23,6 +23,7 @@ static const int DEPRECATION_WARN_LIMIT = 14 * 24 * EXPECTED_BLOCKS_PER_HOUR;
 //! Defaults for -allowdeprecated
 static const std::set<std::string> DEFAULT_ALLOW_DEPRECATED{{
     // Node-level features
+    "gbt_oldhashes"
 
     // Wallet-level features
 #ifdef ENABLE_WALLET
@@ -46,6 +47,7 @@ static const std::set<std::string> DEFAULT_DENY_DEPRECATED{{
 }};
 
 // Flags that enable deprecated functionality.
+extern bool fEnableGbtOldHashes;
 #ifdef ENABLE_WALLET
 extern bool fEnableGetNewAddress;
 extern bool fEnableGetRawChangeAddress;

src/rpc/mining.cpp

@@ -14,6 +14,7 @@
 #ifdef ENABLE_MINING
 #include "crypto/equihash.h"
 #endif
+#include "deprecation.h"
 #include "init.h"
 #include "key_io.h"
 #include "main.h"
@@ -782,9 +783,11 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
     result.pushKV("version", pblock->nVersion);
     result.pushKV("previousblockhash", pblock->hashPrevBlock.GetHex());
     // The following 3 are deprecated; remove in a future release.
-    result.pushKV("blockcommitmentshash", pblock->hashBlockCommitments.GetHex());
-    result.pushKV("lightclientroothash", pblock->hashBlockCommitments.GetHex());
-    result.pushKV("finalsaplingroothash", pblock->hashBlockCommitments.GetHex());
+    if (fEnableGbtOldHashes) {
+        result.pushKV("blockcommitmentshash", pblock->hashBlockCommitments.GetHex());
+        result.pushKV("lightclientroothash", pblock->hashBlockCommitments.GetHex());
+        result.pushKV("finalsaplingroothash", pblock->hashBlockCommitments.GetHex());
+    }
     {
         // These are items in the result object that are valid only if the
         // block template returned by this RPC is used unmodified. Otherwise,