cli: extract connection exception handler, -rpcwait logic

to ConnectAndCallRPC() to be callable for individual connections.

This is needed for RPCs that need to be called and handled sequentially, rather
than alone or in a batch.

For example, when fetching the balances for each loaded wallet, -getinfo will
call RPC listwallets, and then, depending on the result, RPC getbalances.

It may be somewhat helpful to review this commit with `git show -w`.

1 files changed, 64 insertions, 51 deletions

diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
index cdaabd6fab..fd3a007dbb 100644
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -418,6 +418,40 @@ static UniValue CallRPC(BaseRequestHandler *rh, const std::string& strMethod, co
     return reply;
 }
 
+/**
+ * ConnectAndCallRPC wraps CallRPC with -rpcwait and an exception handler.
+ *
+ * @param[in] rh         Pointer to RequestHandler.
+ * @param[in] strMethod  Reference to const string method to forward to CallRPC.
+ * @returns the RPC response as a UniValue object.
+ * @throws a CConnectionFailed std::runtime_error if connection failed or RPC server still in warmup.
+ */
+static UniValue ConnectAndCallRPC(BaseRequestHandler* rh, const std::string& strMethod, const std::vector<std::string>& args)
+{
+    UniValue response(UniValue::VOBJ);
+    // Execute and handle connection failures with -rpcwait.
+    const bool fWait = gArgs.GetBoolArg("-rpcwait", false);
+    do {
+        try {
+            response = CallRPC(rh, strMethod, args);
+            if (fWait) {
+                const UniValue& error = find_value(response, "error");
+                if (!error.isNull() && error["code"].get_int() == RPC_IN_WARMUP) {
+                    throw CConnectionFailed("server in warmup");
+                }
+            }
+            break; // Connection succeeded, no need to retry.
+        } catch (const CConnectionFailed&) {
+            if (fWait) {
+                UninterruptibleSleep(std::chrono::milliseconds{1000});
+            } else {
+                throw;
+            }
+        }
+    } while (fWait);
+    return response;
+}
+
 static int CommandLineRPC(int argc, char *argv[])
 {
     std::string strPrint;
@@ -485,62 +519,41 @@ static int CommandLineRPC(int argc, char *argv[])
             method = args[0];
             args.erase(args.begin()); // Remove trailing method name from arguments vector
         }
-
-        // Execute and handle connection failures with -rpcwait
-        const bool fWait = gArgs.GetBoolArg("-rpcwait", false);
-        do {
-            try {
-                const UniValue reply = CallRPC(rh.get(), method, args);
-
-                // Parse reply
-                const UniValue& result = find_value(reply, "result");
-                const UniValue& error  = find_value(reply, "error");
-
-                if (!error.isNull()) {
-                    // Error
-                    int code = error["code"].get_int();
-                    if (fWait && code == RPC_IN_WARMUP)
-                        throw CConnectionFailed("server in warmup");
-                    strPrint = "error: " + error.write();
-                    nRet = abs(code);
-                    if (error.isObject())
-                    {
-                        UniValue errCode = find_value(error, "code");
-                        UniValue errMsg  = find_value(error, "message");
-                        strPrint = errCode.isNull() ? "" : "error code: "+errCode.getValStr()+"\n";
-
-                        if (errMsg.isStr())
-                            strPrint += "error message:\n"+errMsg.get_str();
-
-                        if (errCode.isNum() && errCode.get_int() == RPC_WALLET_NOT_SPECIFIED) {
-                            strPrint += "\nTry adding \"-rpcwallet=<filename>\" option to bitcoin-cli command line.";
-                        }
-                    }
-                } else {
-                    // Result
-                    if (result.isNull())
-                        strPrint = "";
-                    else if (result.isStr())
-                        strPrint = result.get_str();
-                    else
-                        strPrint = result.write(2);
+        const UniValue reply = ConnectAndCallRPC(rh.get(), method, args);
+
+        // Parse reply
+        UniValue result = find_value(reply, "result");
+        const UniValue& error = find_value(reply, "error");
+        if (!error.isNull()) {
+            // Error
+            strPrint = "error: " + error.write();
+            nRet = abs(error["code"].get_int());
+            if (error.isObject()) {
+                const UniValue& errCode = find_value(error, "code");
+                const UniValue& errMsg = find_value(error, "message");
+                strPrint = errCode.isNull() ? "" : ("error code: " + errCode.getValStr() + "\n");
+
+                if (errMsg.isStr()) {
+                    strPrint += ("error message:\n" + errMsg.get_str());
+                }
+                if (errCode.isNum() && errCode.get_int() == RPC_WALLET_NOT_SPECIFIED) {
+                    strPrint += "\nTry adding \"-rpcwallet=<filename>\" option to bitcoin-cli command line.";
                 }
-                // Connection succeeded, no need to retry.
-                break;
             }
-            catch (const CConnectionFailed&) {
-                if (fWait)
-                    UninterruptibleSleep(std::chrono::milliseconds{1000});
-                else
-                    throw;
+        } else {
+            // Result
+            if (result.isNull()) {
+                strPrint = "";
+            } else if (result.isStr()) {
+                strPrint = result.get_str();
+            } else {
+                strPrint = result.write(2);
             }
-        } while (fWait);
-    }
-    catch (const std::exception& e) {
+        }
+    } catch (const std::exception& e) {
         strPrint = std::string("error: ") + e.what();
         nRet = EXIT_FAILURE;
-    }
-    catch (...) {
+    } catch (...) {
         PrintExceptionContinue(nullptr, "CommandLineRPC()");
         throw;
     }