Fix CI: -Werror=type-limits and accumulated cpplint errors

When TASK-003..008 were merged into feature/v2.0 they were not pushed
individually, so the cumulative push surfaced regressions across the
matrix. This sweeps them up.

Build error (basic ubuntu / valgrind / windows-IWYU):
- test/unit/body_test.cpp:56-60: static_cast<int>(uint8_t-enum) >= 0
  is always-true, breaking -Werror=type-limits. Replace with
  enumerator != body_kind::empty so the compile-time reference still
  guards against a missing enumerator without the bogus comparison.

cpplint (17 errors → 0):
- Include order:
  - src/details/body.cpp, src/iovec_response.cpp,
    src/httpserver/details/body.hpp,
    test/unit/{body_test,header_hygiene_test,http_method_test,
    iovec_entry_test}.cpp: move <microhttpd.h> and <sys/uio.h> into
    the C-system-header group so the layout is primary, c, c++, other.
- Missing includes:
  - src/details/body.cpp, src/iovec_response.cpp: add <string> for
    std::string in the file_body / iovec_response signatures.
  - src/iovec_response.cpp: add <utility> for std::move.
- Header guard:
  - src/httpserver/details/body.hpp: cpplint expects #ifndef GUARD as
    the first non-comment line. Move the SRC_HTTPSERVER_DETAILS_BODY_HPP_
    guard above the HTTPSERVER_COMPILATION #error block (which now
    lives inside the guard).
- Misc:
  - body_kind.hpp: NOLINT(build/include_what_you_use) on the `string`
    enumerator (cpplint mistook it for std::string).
  - body_test.cpp:251: split single-line if-with-multiple-statements.
  - http_method_test.cpp:121: add space between [] and { in lambda.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: etr

src/details/body.cpp

@@ -21,6 +21,7 @@
 #include "httpserver/details/body.hpp"
 
 #include <fcntl.h>
+#include <microhttpd.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/uio.h>
@@ -29,11 +30,10 @@
 #include <cstddef>
 #include <cstdint>
 #include <limits>
+#include <string>
 #include <type_traits>
 #include <utility>
 
-#include <microhttpd.h>
-
 namespace httpserver {
 
 namespace detail {

src/httpserver/body_kind.hpp

@@ -45,7 +45,7 @@ namespace httpserver {
 // name the enumerators).
 enum class body_kind : std::uint8_t {
     empty,
-    string,
+    string,    // NOLINT(build/include_what_you_use) - enumerator, not std::string
     file,
     iovec,
     pipe,

src/httpserver/details/body.hpp

@@ -28,14 +28,17 @@
 //
 // Header-hygiene contract: only library .cpp files (and build-tree unit
 // tests compiled with -DHTTPSERVER_COMPILATION) may include this file.
+#ifndef SRC_HTTPSERVER_DETAILS_BODY_HPP_
+#define SRC_HTTPSERVER_DETAILS_BODY_HPP_
+
 #ifndef HTTPSERVER_COMPILATION
 #error "details/body.hpp is internal; build with -DHTTPSERVER_COMPILATION."
 #endif
 
-#ifndef SRC_HTTPSERVER_DETAILS_BODY_HPP_
-#define SRC_HTTPSERVER_DETAILS_BODY_HPP_
-
+#include <microhttpd.h>
 #include <sys/types.h>      // ssize_t
+#include <sys/uio.h>        // private header may include POSIX scatter/gather
+
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
@@ -44,9 +47,6 @@
 #include <utility>
 #include <vector>
 
-#include <microhttpd.h>
-#include <sys/uio.h>        // private header may include POSIX scatter/gather
-
 #include "httpserver/body_kind.hpp"
 #include "httpserver/iovec_entry.hpp"
 

src/iovec_response.cpp

@@ -19,15 +19,19 @@
 */
 
 #include "httpserver/iovec_response.hpp"
-#include "httpserver/iovec_entry.hpp"
 
-#include <cstddef>
-#include <limits>
 #include <microhttpd.h>
 #include <sys/uio.h>
+
+#include <cstddef>
+#include <limits>
+#include <string>
 #include <type_traits>
+#include <utility>
 #include <vector>
 
+#include "httpserver/iovec_entry.hpp"
+
 struct MHD_Response;
 
 namespace httpserver {

test/unit/body_test.cpp

@@ -24,8 +24,10 @@
 // details/body.hpp directly (for the subclasses) — header-hygiene from
 // the consumer perspective is asserted separately by header_hygiene_*.
 
+#include <microhttpd.h>
 #include <sys/types.h>      // ssize_t
 #include <unistd.h>         // pipe, close
+
 #include <cerrno>
 #include <cstdint>
 #include <cstring>
@@ -36,8 +38,6 @@
 #include <utility>
 #include <vector>
 
-#include <microhttpd.h>
-
 #include "./httpserver.hpp"                 // public umbrella → body_kind
 #include "httpserver/details/body.hpp"      // private hierarchy
 #include "./littletest.hpp"
@@ -53,11 +53,13 @@ static_assert(std::is_same_v<std::underlying_type_t<httpserver::body_kind>,
 static_assert(static_cast<int>(httpserver::body_kind::empty) == 0,
               "body_kind::empty must be the zero-initialised value");
 // Reference each enumerator at compile time so a missing one breaks the build.
-static_assert(static_cast<int>(httpserver::body_kind::string) >= 0);
-static_assert(static_cast<int>(httpserver::body_kind::file) >= 0);
-static_assert(static_cast<int>(httpserver::body_kind::iovec) >= 0);
-static_assert(static_cast<int>(httpserver::body_kind::pipe) >= 0);
-static_assert(static_cast<int>(httpserver::body_kind::deferred) >= 0);
+// Comparing against `empty` (=0) avoids -Wtype-limits on uint8_t-backed enums
+// while still touching every name.
+static_assert(httpserver::body_kind::string   != httpserver::body_kind::empty);
+static_assert(httpserver::body_kind::file     != httpserver::body_kind::empty);
+static_assert(httpserver::body_kind::iovec    != httpserver::body_kind::empty);
+static_assert(httpserver::body_kind::pipe     != httpserver::body_kind::empty);
+static_assert(httpserver::body_kind::deferred != httpserver::body_kind::empty);
 
 // -----------------------------------------------------------------------
 // Step 2 — abstract base contract.
@@ -248,7 +250,11 @@ LT_BEGIN_AUTO_TEST(body_suite, deferred_body_trampoline_invokes_stored_callable)
         [&](uint64_t pos, char* buf, std::size_t max) -> ssize_t {
             called = true;
             (void)pos;
-            if (max >= 2) { buf[0] = 'h'; buf[1] = 'i'; return 2; }
+            if (max >= 2) {
+                buf[0] = 'h';
+                buf[1] = 'i';
+                return 2;
+            }
             return 0;
         });
     char out[16] = {};

test/unit/header_hygiene_test.cpp

@@ -63,10 +63,10 @@
 // preprocessor-grep target `make check-hygiene` in the top-level
 // Makefile.am. Keep both lists in sync.
 
-#include <httpserver.hpp>
-
 #include <cstdio>
 
+#include <httpserver.hpp>
+
 int main() {
     int leaks = 0;
 

test/unit/http_method_test.cpp

@@ -23,8 +23,9 @@
 // layout / width pinning, bitwise composition, complement bounding,
 // to_string totality, and round-trip via set/contains.
 
-#include <cstdint>
 #include <microhttpd.h>
+
+#include <cstdint>
 #include <string_view>
 #include <type_traits>
 
@@ -118,7 +119,7 @@ static_assert((~httpserver::http_method::get)
                   .contains(httpserver::http_method::post));
 
 // Compound assignment usable in constant context.
-static_assert([]{
+static_assert([] {
     httpserver::method_set s{};
     s |= httpserver::http_method::get;
     s |= httpserver::http_method::post;

test/unit/iovec_entry_test.cpp

@@ -24,9 +24,10 @@
 // guarantee that downstream code does NOT see <sys/uio.h> via the umbrella
 // is asserted separately by `header_hygiene_iovec_test.cpp`.
 
-#include <cstddef>
 #include <microhttpd.h>
 #include <sys/uio.h>
+
+#include <cstddef>
 #include <type_traits>
 
 #include "./httpserver.hpp"