Merge bitcoin#24155: doc: Fix rpc docs

fac8caa doc: Fix rpc docs (MarcoFalke)

Pull request description:

  Broken in commit 39d9bbe.

  The fix removes the "type" `OBJ_EMPTY` added in commit 8d1a3e6, which isn't really a separate type and instead runs a check on `OBJ` whether it is empty or not.

ACKs for top commit:
  Sjors:
    tACK fac8caa

Tree-SHA512: dd978fe526a45095800249204afd26a239078e83b15124a5756ac078c473a677a3084b8f54e34d6dd5580abef7275c875a14bc9eb20d8feab066dfb0f0932967

Author: fanquake

src/rpc/blockchain.cpp

@@ -473,15 +473,15 @@ static RPCHelpMan getblockfrompeer()
 {
     return RPCHelpMan{
         "getblockfrompeer",
-        "\nAttempt to fetch block from a given peer.\n"
+        "Attempt to fetch block from a given peer.\n"
         "\nWe must have the header for this block, e.g. using submitheader.\n"
         "Subsequent calls for the same block and a new peer will cause the response from the previous peer to be ignored.\n"
         "\nReturns an empty JSON object if the request was successfully scheduled.",
         {
             {"block_hash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The block hash to try to fetch"},
             {"peer_id", RPCArg::Type::NUM, RPCArg::Optional::NO, "The peer to fetch it from (see getpeerinfo for peer IDs)"},
         },
-        RPCResult{RPCResult::Type::OBJ_EMPTY, "", /*optional=*/ false, "", {}},
+        RPCResult{RPCResult::Type::OBJ, "", /*optional=*/false, "", {}},
         RPCExamples{
             HelpExampleCli("getblockfrompeer", "\"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09\" 0")
             + HelpExampleRpc("getblockfrompeer", "\"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09\" 0")

src/rpc/util.cpp

@@ -791,16 +791,15 @@ void RPCResult::ToSections(Sections& sections, const OuterType outer_type, const
         return;
     }
     case Type::OBJ_DYN:
-    case Type::OBJ_EMPTY: {
-        sections.PushSection({indent + maybe_key + "{}", Description("empty JSON object")});
-        return;
-    }
     case Type::OBJ: {
+        if (m_inner.empty()) {
+            sections.PushSection({indent + maybe_key + "{}", Description("empty JSON object")});
+            return;
+        }
         sections.PushSection({indent + maybe_key + "{", Description("json object")});
         for (const auto& i : m_inner) {
             i.ToSections(sections, OuterType::OBJ, current_indent + 2);
         }
-        CHECK_NONFATAL(!m_inner.empty());
         if (m_type == Type::OBJ_DYN && m_inner.back().m_type != Type::ELISION) {
             // If the dictionary keys are dynamic, use three dots for continuation
             sections.PushSection({indent_next + "...", ""});
@@ -844,14 +843,24 @@ bool RPCResult::MatchesType(const UniValue& result) const
         return UniValue::VARR == result.getType();
     }
     case Type::OBJ_DYN:
-    case Type::OBJ_EMPTY:
     case Type::OBJ: {
         return UniValue::VOBJ == result.getType();
     }
     } // no default case, so the compiler can warn about missing cases
     NONFATAL_UNREACHABLE();
 }
 
+void RPCResult::CheckInnerDoc() const
+{
+    if (m_type == Type::OBJ) {
+        // May or may not be empty
+        return;
+    }
+    // Everything else must either be empty or not
+    const bool inner_needed{m_type == Type::ARR || m_type == Type::ARR_FIXED || m_type == Type::OBJ_DYN};
+    CHECK_NONFATAL(inner_needed != m_inner.empty());
+}
+
 std::string RPCArg::ToStringObj(const bool oneline) const
 {
     std::string res;

src/rpc/util.h

@@ -250,7 +250,6 @@ struct RPCResult {
         STR_AMOUNT, //!< Special string to represent a floating point amount
         STR_HEX,    //!< Special string with only hex chars
         OBJ_DYN,    //!< Special dictionary with keys that are not literals
-        OBJ_EMPTY,  //!< Special type to allow empty OBJ
         ARR_FIXED,  //!< Special array that has a fixed number of entries
         NUM_TIME,   //!< Special numeric to denote unix epoch time
         ELISION,    //!< Special type to denote elision (...)
@@ -278,8 +277,7 @@ struct RPCResult {
           m_cond{std::move(cond)}
     {
         CHECK_NONFATAL(!m_cond.empty());
-        const bool inner_needed{type == Type::ARR || type == Type::ARR_FIXED || type == Type::OBJ || type == Type::OBJ_DYN};
-        CHECK_NONFATAL(inner_needed != inner.empty());
+        CheckInnerDoc();
     }
 
     RPCResult(
@@ -303,8 +301,7 @@ struct RPCResult {
           m_description{std::move(description)},
           m_cond{}
     {
-        const bool inner_needed{type == Type::ARR || type == Type::ARR_FIXED || type == Type::OBJ || type == Type::OBJ_DYN};
-        CHECK_NONFATAL(inner_needed != inner.empty());
+        CheckInnerDoc();
     }
 
     RPCResult(
@@ -322,6 +319,9 @@ struct RPCResult {
     std::string ToDescriptionString() const;
     /** Check whether the result JSON type matches. */
     bool MatchesType(const UniValue& result) const;
+
+private:
+    void CheckInnerDoc() const;
 };
 
 struct RPCResults {