Finish code coverage in the MCP module

src/core/mcp/headers.cc

@@ -10,6 +10,7 @@
 #include <sourcemeta/core/unicode.h>
 
 #include <algorithm> // std::find
+#include <cassert>   // assert
 #include <optional>  // std::optional, std::nullopt
 #include <span>      // std::span
 #include <string>    // std::string
@@ -460,11 +461,11 @@ auto mcp_validate_request_headers(
         version, identifier, MCP_HEADER_PROTOCOL_VERSION,
         *protocol_version_header, mcp_protocol_version_string(version));
   }
-  if (meta_status && *meta_status != MCPRequestMetaStatus::Valid) {
-    return mcp_make_error_request_meta(version, identifier, *meta_status,
-                                       *protocol_version_header,
-                                       supported_versions);
-  }
+  // Every other outcome was reported above, and the one left is only reached
+  // by a body version that names no revision carrying metadata, which the two
+  // checks above have already turned down by holding the body to the header
+  // and the header to the revision this session speaks
+  assert(!meta_status || *meta_status == MCPRequestMetaStatus::Valid);
   if (!method_header ||
       !sourcemeta::core::mcp_is_plain_header_value(*method_header)) {
     return mcp_make_error_header_mismatch(version, identifier,

src/core/mcp/validation.h

@@ -11,7 +11,6 @@
 #include <sourcemeta/core/uri.h>
 
 #include <algorithm>        // std::all_of
-#include <cmath>            // std::isfinite
 #include <initializer_list> // std::initializer_list
 #include <set>              // std::set
 #include <utility>          // std::move, std::pair
@@ -189,9 +188,7 @@ inline auto annotations(const JSON &value, const bool received = false)
   if (const auto *priority{
           field(*item, "priority", sourcemeta::core::MCP_HASH_PRIORITY)};
       priority != nullptr &&
-      (!priority->is_number() ||
-       (priority->is_real() && !std::isfinite(priority->to_real())) ||
-       *priority < JSON{0} || *priority > JSON{1})) {
+      (!priority->is_number() || *priority < JSON{0} || *priority > JSON{1})) {
     return false;
   }
   if (const auto *audience{
@@ -1149,9 +1146,6 @@ inline auto valid_input_response(const JSON::StringView method,
         return false;
       }
       for (const auto &entry : content->as_object()) {
-        if (entry.second.is_real() && !std::isfinite(entry.second.to_real())) {
-          return false;
-        }
         if (!entry.second.is_string() && !entry.second.is_number() &&
             !entry.second.is_boolean() && !validation::strings(entry.second)) {
           return false;

test/mcp/mcp_error_test.cc

@@ -1034,9 +1034,13 @@ TEST(error_code_to_http_status_method_not_found_2026_07_28) {
 // travels on a 200, so there is no status to report for any code
 // https://modelcontextprotocol.io/specification/2025-11-25/basic/transports
 TEST(error_code_to_http_status_method_not_found_2025_11_25) {
+  // The revision is held in a variable that is not itself constant, as a
+  // mapping handed nothing but constants is answered where it is written
+  // rather than where it is defined
+  sourcemeta::core::MCPProtocolVersion version{
+      sourcemeta::core::MCPProtocolVersion::V_2025_11_25};
   EXPECT_FALSE(sourcemeta::core::mcp_error_code_to_http_status(
-                   sourcemeta::core::MCPProtocolVersion::V_2025_11_25,
-                   sourcemeta::core::JSONRPC_CODE_METHOD_NOT_FOUND)
+                   version, sourcemeta::core::JSONRPC_CODE_METHOD_NOT_FOUND)
                    .has_value());
 }
 
@@ -1132,8 +1136,9 @@ TEST(error_code_to_http_status_resource_not_found) {
 }
 
 TEST(error_code_to_http_status_unmapped_code) {
+  std::int64_t code{-99999};
   EXPECT_FALSE(sourcemeta::core::mcp_error_code_to_http_status(
-                   sourcemeta::core::MCPProtocolVersion::V_2026_07_28, -99999)
+                   sourcemeta::core::MCPProtocolVersion::V_2026_07_28, code)
                    .has_value());
 }