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Improve MCP validation efficiency and annotate public APIs with nodiscard #3024

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24 changes: 12 additions & 12 deletions src/core/mcp/include/sourcemeta/core/mcp_capabilities.h
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Original file line number Diff line number Diff line change
Expand Up @@ -168,9 +168,9 @@ struct MCPServerCapabilities {
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/schema#clientcapabilities
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_parse_client_capabilities(const MCPProtocolVersion version,
const sourcemeta::core::JSON &capabilities)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_parse_client_capabilities(const MCPProtocolVersion version,
const sourcemeta::core::JSON &capabilities)
-> MCPClientCapabilities;

/// @ingroup mcp
Expand Down Expand Up @@ -199,9 +199,9 @@ auto mcp_parse_client_capabilities(const MCPProtocolVersion version,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/schema#clientcapabilities
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_serialize_client_capabilities(
const MCPProtocolVersion version, const MCPClientCapabilities &capabilities)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_serialize_client_capabilities(const MCPProtocolVersion version,
const MCPClientCapabilities &capabilities)
-> sourcemeta::core::JSON;

/// @ingroup mcp
Expand All @@ -226,9 +226,9 @@ auto mcp_serialize_client_capabilities(
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/schema#servercapabilities
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_parse_server_capabilities(MCPProtocolVersion version,
const JSON &capabilities)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_parse_server_capabilities(MCPProtocolVersion version,
const JSON &capabilities)
-> MCPServerCapabilities;

/// @ingroup mcp
Expand All @@ -252,9 +252,9 @@ auto mcp_parse_server_capabilities(MCPProtocolVersion version,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/schema#servercapabilities
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_serialize_server_capabilities(
MCPProtocolVersion version, const MCPServerCapabilities &capabilities)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_serialize_server_capabilities(MCPProtocolVersion version,
const MCPServerCapabilities &capabilities)
-> JSON;

} // namespace sourcemeta::core
Expand Down
56 changes: 25 additions & 31 deletions src/core/mcp/include/sourcemeta/core/mcp_error.h
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Expand Up @@ -109,11 +109,11 @@ enum class MCPErrorContext : std::uint8_t {
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#responses
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error(MCPProtocolVersion version, const JSON *identifier,
std::int64_t code, JSON::StringView message,
std::optional<JSON> data = std::nullopt,
MCPErrorContext context = MCPErrorContext::Request) -> JSON;
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
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mcp_make_error(MCPProtocolVersion version, const JSON *identifier,
std::int64_t code, JSON::StringView message,
std::optional<JSON> data = std::nullopt,
MCPErrorContext context = MCPErrorContext::Request) -> JSON;

/// @ingroup mcp
/// The legacy MCP error code returned when a requested resource cannot be
Expand Down Expand Up @@ -196,8 +196,9 @@ constexpr std::int64_t MCP_CODE_UNSUPPORTED_PROTOCOL_VERSION{-32022};
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#server-validation
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#_meta
constexpr auto mcp_error_code_to_http_status(const MCPProtocolVersion version,
const std::int64_t code) noexcept
[[nodiscard]] constexpr auto
mcp_error_code_to_http_status(const MCPProtocolVersion version,
const std::int64_t code) noexcept
-> std::optional<HTTPStatus> {
if (version != MCPProtocolVersion::V_2026_07_28) {
return std::nullopt;
Expand Down Expand Up @@ -247,8 +248,8 @@ constexpr auto mcp_error_code_to_http_status(const MCPProtocolVersion version,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#error-codes
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_unsupported_protocol_version(
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_make_error_unsupported_protocol_version(
const MCPProtocolVersion version, const sourcemeta::core::JSON *identifier,
const JSON::StringView requested,
const std::span<const JSON::StringView> supported)
Expand Down Expand Up @@ -282,8 +283,8 @@ auto mcp_make_error_unsupported_protocol_version(
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#error-codes
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_missing_required_capability(
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_make_error_missing_required_capability(
const MCPProtocolVersion version, const sourcemeta::core::JSON *identifier,
sourcemeta::core::JSON required_capabilities,
const JSON::StringView message) -> sourcemeta::core::JSON;
Expand All @@ -310,11 +311,9 @@ auto mcp_make_error_missing_required_capability(
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#schema-extension
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_header_mismatch(const MCPProtocolVersion version,
const sourcemeta::core::JSON *identifier,
const JSON::StringView message)
-> sourcemeta::core::JSON;
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_make_error_header_mismatch(
const MCPProtocolVersion version, const sourcemeta::core::JSON *identifier,
const JSON::StringView message) -> sourcemeta::core::JSON;

/// @ingroup mcp
/// Build a JSON-RPC error response for header mismatch (-32020) with detailed
Expand Down Expand Up @@ -346,13 +345,10 @@ auto mcp_make_error_header_mismatch(const MCPProtocolVersion version,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#schema-extension
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_header_mismatch(const MCPProtocolVersion version,
const sourcemeta::core::JSON *identifier,
const JSON::StringView header_name,
const JSON::StringView header_value,
const JSON::StringView body_value)
-> sourcemeta::core::JSON;
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_make_error_header_mismatch(
const MCPProtocolVersion version, const sourcemeta::core::JSON *identifier,
const JSON::StringView header_name, const JSON::StringView header_value,
const JSON::StringView body_value) -> sourcemeta::core::JSON;

/// @ingroup mcp
/// Build a JSON-RPC error response for header mismatch (-32020) reporting an
Expand All @@ -379,11 +375,9 @@ auto mcp_make_error_header_mismatch(const MCPProtocolVersion version,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#schema-extension
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_header_mismatch(const MCPProtocolVersion version,
const sourcemeta::core::JSON *identifier,
const JSON::StringView header_name,
const JSON::StringView header_value)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_make_error_header_mismatch(
const MCPProtocolVersion version, const sourcemeta::core::JSON *identifier,
const JSON::StringView header_name, const JSON::StringView header_value)
-> sourcemeta::core::JSON;

/// @ingroup mcp
Expand Down Expand Up @@ -414,9 +408,9 @@ auto mcp_make_error_header_mismatch(const MCPProtocolVersion version,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/server/resources#error-handling
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_resource_not_found(const MCPProtocolVersion version,
const sourcemeta::core::JSON *identifier)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_make_error_resource_not_found(const MCPProtocolVersion version,
const sourcemeta::core::JSON *identifier)
-> sourcemeta::core::JSON;

} // namespace sourcemeta::core
Expand Down
34 changes: 15 additions & 19 deletions src/core/mcp/include/sourcemeta/core/mcp_headers.h
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Original file line number Diff line number Diff line change
Expand Up @@ -141,8 +141,8 @@ struct MCPRequestMeta {
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#_meta
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_validate_request_meta(const sourcemeta::core::JSON &envelope)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_validate_request_meta(const sourcemeta::core::JSON &envelope)
-> std::pair<MCPRequestMetaStatus, std::optional<MCPRequestMeta>>;

/// @ingroup mcp
Expand All @@ -166,8 +166,8 @@ auto mcp_validate_request_meta(const sourcemeta::core::JSON &envelope)
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#_meta
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_validate_request_parameters(const JSON &parameters)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_validate_request_parameters(const JSON &parameters)
-> std::pair<MCPRequestMetaStatus, std::optional<MCPRequestMeta>>;

/// @ingroup mcp
Expand Down Expand Up @@ -216,8 +216,7 @@ auto mcp_validate_request_parameters(const JSON &parameters)
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/index#error-codes
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_error_request_meta(
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_make_error_request_meta(
const MCPProtocolVersion version, const sourcemeta::core::JSON *identifier,
const MCPRequestMetaStatus status, const JSON::StringView requested,
const std::span<const JSON::StringView> supported)
Expand All @@ -242,8 +241,8 @@ auto mcp_make_error_request_meta(
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#standard-request-headers
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_request_name_from_body(const sourcemeta::core::JSON &envelope)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_request_name_from_body(const sourcemeta::core::JSON &envelope)
-> std::optional<JSON::StringView>;

/// @ingroup mcp
Expand Down Expand Up @@ -285,8 +284,7 @@ auto mcp_request_name_from_body(const sourcemeta::core::JSON &envelope)
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#server-validation
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_validate_request_headers(
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_validate_request_headers(
const MCPProtocolVersion version,
const std::optional<JSON::StringView> &protocol_version_header,
const std::optional<JSON::StringView> &method_header,
Expand Down Expand Up @@ -316,8 +314,8 @@ auto mcp_validate_request_headers(
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#value-encoding
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_encode_header_value(JSON::StringView value) -> std::string;
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_encode_header_value(JSON::StringView value) -> std::string;

/// @ingroup mcp
/// Validate a borrowed HTTP header collection. Names are case insensitive.
Expand Down Expand Up @@ -363,8 +361,7 @@ auto mcp_encode_header_value(JSON::StringView value) -> std::string;
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#server-validation
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_validate_request_headers(
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_validate_request_headers(
MCPProtocolVersion version,
std::span<const std::pair<JSON::StringView, JSON::StringView>> headers,
const JSON &envelope, std::span<const JSON::StringView> supported_versions)
Expand Down Expand Up @@ -442,9 +439,9 @@ struct MCPHeaderParameter {
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#schema-extension
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_make_parameter_headers(std::span<const MCPHeaderParameter> parameters,
const JSON &arguments)
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto
mcp_make_parameter_headers(std::span<const MCPHeaderParameter> parameters,
const JSON &arguments)
-> std::vector<std::pair<std::string, std::string>>;

/// @ingroup mcp
Expand Down Expand Up @@ -478,8 +475,7 @@ auto mcp_make_parameter_headers(std::span<const MCPHeaderParameter> parameters,
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http#server-validation
SOURCEMETA_CORE_MCP_EXPORT
auto mcp_validate_parameter_headers(
[[nodiscard]] SOURCEMETA_CORE_MCP_EXPORT auto mcp_validate_parameter_headers(
MCPProtocolVersion version, const JSON &identifier,
std::span<const MCPHeaderParameter> parameters, const JSON &arguments,
std::span<const std::pair<JSON::StringView, JSON::StringView>> headers)
Expand Down
13 changes: 7 additions & 6 deletions src/core/mcp/include/sourcemeta/core/mcp_logging.h
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Expand Up @@ -55,8 +55,8 @@ enum class MCPLogLevel : std::uint8_t {
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/server/utilities/logging
constexpr auto mcp_log_level_string(const MCPLogLevel level) noexcept
-> JSON::StringView {
[[nodiscard]] constexpr auto
mcp_log_level_string(const MCPLogLevel level) noexcept -> JSON::StringView {
switch (level) {
case MCPLogLevel::Debug:
return "debug";
Expand Down Expand Up @@ -99,7 +99,8 @@ constexpr auto mcp_log_level_string(const MCPLogLevel level) noexcept
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/server/utilities/logging
constexpr auto mcp_resolve_log_level(const JSON::StringView value) noexcept
[[nodiscard]] constexpr auto
mcp_resolve_log_level(const JSON::StringView value) noexcept
-> std::optional<MCPLogLevel> {
constexpr std::array<MCPLogLevel, 8> LEVELS{
{MCPLogLevel::Debug, MCPLogLevel::Info, MCPLogLevel::Notice,
Expand Down Expand Up @@ -135,9 +136,9 @@ constexpr auto mcp_resolve_log_level(const JSON::StringView value) noexcept
///
/// @see
/// https://modelcontextprotocol.io/specification/2026-07-28/server/utilities/logging
constexpr auto mcp_log_level_enabled(const MCPLogLevel level,
const MCPLogLevel threshold) noexcept
-> bool {
[[nodiscard]] constexpr auto
mcp_log_level_enabled(const MCPLogLevel level,
const MCPLogLevel threshold) noexcept -> bool {
return level >= threshold;
}

Expand Down
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