[wallet] Deprecate the generate RPC method

Author: jnewbery

doc/release-notes-14468.md

@@ -0,0 +1,15 @@
+Wallet `generate` RPC method deprecated
+---------------------------------------
+
+The wallet's `generate` RPC method has been deprecated and will be fully
+removed in v0.19.
+
+`generate` is only used for testing. The RPC call reaches across multiple
+subsystems (wallet and mining), so is deprecated to simplify the wallet-node
+interface. Projects that are using `generate` for testing purposes should
+transition to using the `generatetoaddress` call, which does not require or use
+the wallet component. Calling `generatetoaddress` with an address returned by
+`getnewaddress` gives the same functionality as the old `generate` method.
+
+To continue using `generate` in v0.18, restart bitcoind with the
+`-deprecatedrpc=generate` configuration.

src/wallet/rpcwallet.cpp

@@ -3289,6 +3289,12 @@ UniValue generate(const JSONRPCRequest& request)
         );
     }
 
+    if (!IsDeprecatedRPCEnabled("generate")) {
+        throw JSONRPCError(RPC_METHOD_DEPRECATED, "The wallet generate rpc method is deprecated and will be fully removed in v0.19. "
+            "To use generate in v0.18, restart bitcoind with -deprecatedrpc=generate.\n"
+            "Clients should transition to using the node rpc method generatetoaddress\n");
+    }
+
     int num_generate = request.params[0].get_int();
     uint64_t max_tries = 1000000;
     if (!request.params[1].isNull()) {

test/functional/rpc_deprecated.py

@@ -4,12 +4,17 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test deprecation of RPC calls."""
 from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_raises_rpc_error
 
 class DeprecatedRpcTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
         self.setup_clean_chain = True
-        self.extra_args = [[], ["-deprecatedrpc=validateaddress"]]
+        self.extra_args = [[], ["-deprecatedrpc=generate"]]
+
+    def skip_test_if_missing_module(self):
+        # The generate RPC method requires the wallet to be compiled
+        self.skip_if_no_wallet()
 
     def run_test(self):
         # This test should be used to verify correct behaviour of deprecated
@@ -18,7 +23,10 @@ def run_test(self):
         # self.log.info("Make sure that -deprecatedrpc=createmultisig allows it to take addresses")
         # assert_raises_rpc_error(-5, "Invalid public key", self.nodes[0].createmultisig, 1, [self.nodes[0].getnewaddress()])
         # self.nodes[1].createmultisig(1, [self.nodes[1].getnewaddress()])
-        pass
+
+        self.log.info("Test generate RPC")
+        assert_raises_rpc_error(-32, 'The wallet generate rpc method is deprecated', self.nodes[0].rpc.generate, 1)
+        self.nodes[1].generate(1)
 
 if __name__ == '__main__':
     DeprecatedRpcTest().main()