docs: update installation guide for vendored cpp-httplib fallback

Remove manual source install instructions for Humble - the vendored
fallback handles this automatically. Update troubleshooting section
and cmake error message accordingly.

Author: bburda

docs/installation.rst

@@ -36,25 +36,10 @@ for your distribution:
 
 .. note::
 
-   On Ubuntu 22.04 (Humble), the ``libcpp-httplib-dev`` system package is either not
-   available or too old (0.10.x). ros2_medkit requires cpp-httplib >= 0.14 for the
-   ``httplib::StatusCode`` enum and ``std::string`` API overloads.
-
-   If ``libcpp-httplib-dev`` is installed, **remove it first** to avoid version conflicts:
-
-   .. code-block:: bash
-
-      sudo apt remove libcpp-httplib-dev
-
-   Then install cpp-httplib >= 0.14 from source:
-
-   .. code-block:: bash
-
-      sudo apt install cmake g++ libssl-dev
-      git clone --depth 1 --branch v0.14.3 https://github.com/yhirose/cpp-httplib.git /tmp/cpp-httplib
-      cd /tmp/cpp-httplib && mkdir build && cd build
-      cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DHTTPLIB_REQUIRE_OPENSSL=ON
-      sudo make install
+   On Ubuntu 22.04 (Humble), the system ``libcpp-httplib-dev`` package provides
+   cpp-httplib 0.10.x which is too old. ros2_medkit requires >= 0.14 but ships a
+   vendored copy as a fallback - no manual installation is needed. The build system
+   automatically uses the vendored header when the system package is insufficient.
 
 Installation from Source
 ------------------------
@@ -176,19 +161,11 @@ Troubleshooting
 
       gcc --version  # Should show 13.x or higher
 
-**Build fails on Humble with** ``httplib::StatusCode has not been declared``
-
-   The system ``libcpp-httplib-dev`` package on Ubuntu 22.04 provides cpp-httplib 0.10.x,
-   which is too old. ros2_medkit requires cpp-httplib >= 0.14. Remove the system package
-   and install from source:
-
-   .. code-block:: bash
+**Build fails on Humble with** ``Could not find cpp-httplib >= 0.14``
 
-      sudo apt remove libcpp-httplib-dev
-      git clone --depth 1 --branch v0.14.3 https://github.com/yhirose/cpp-httplib.git /tmp/cpp-httplib
-      cd /tmp/cpp-httplib && mkdir build && cd build
-      cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DHTTPLIB_REQUIRE_OPENSSL=ON
-      sudo make install
+   This should not happen with current builds - a vendored copy of cpp-httplib 0.14.3
+   is included as an automatic fallback. If you see this error, ensure ``ros2_medkit_cmake``
+   is built before the gateway (``colcon build`` handles this automatically).
 
 **Cannot find ros2_medkit packages after build**
 

src/ros2_medkit_cmake/cmake/ROS2MedkitCompat.cmake

@@ -72,13 +72,13 @@ endmacro()
 # ---------------------------------------------------------------------------
 # medkit_find_cpp_httplib()
 # ---------------------------------------------------------------------------
-# On Jazzy/Noble, libcpp-httplib-dev is available via apt and provides a
-# pkg-config .pc file.  On Humble/Jammy, cpp-httplib must be built from
-# source, which installs a CMake config file (httplibConfig.cmake).
+# Finds cpp-httplib >= 0.14 through a multi-tier fallback chain:
+#   1. pkg-config (Jazzy/Noble system package)
+#   2. cmake find_package(httplib) (source builds, Pixi)
+#   3. VENDORED_DIR parameter (bundled header-only copy)
 #
-# Requires cpp-httplib >= 0.14 (StatusCode enum, std::string overloads).
-# Older system packages (e.g. 0.10.x on Jammy) are rejected by pkg-config
-# so the fallback cmake/source path is used instead.
+# On Humble/Jammy the system package is 0.10.x (too old); the vendored
+# fallback in ros2_medkit_gateway handles this automatically.
 #
 # Creates a unified alias target `cpp_httplib_target` for consumers.
 # ---------------------------------------------------------------------------
@@ -104,14 +104,9 @@ macro(medkit_find_cpp_httplib)
     else()
       message(FATAL_ERROR
         "[MedkitCompat] Could not find cpp-httplib >= 0.14.\n"
-        "  The system libcpp-httplib-dev package on Ubuntu 22.04 provides 0.10.x which is too old.\n"
-        "  ros2_medkit requires cpp-httplib >= 0.14 for httplib::StatusCode and std::string overloads.\n"
-        "  Fix: remove the old system package and install from source:\n"
-        "    sudo apt remove libcpp-httplib-dev\n"
-        "    git clone --depth 1 --branch v0.14.3 https://github.com/yhirose/cpp-httplib.git /tmp/cpp-httplib\n"
-        "    cd /tmp/cpp-httplib && mkdir build && cd build\n"
-        "    cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DHTTPLIB_REQUIRE_OPENSSL=ON\n"
-        "    sudo make install\n"
+        "  Tried: pkg-config, cmake find_package(httplib), VENDORED_DIR.\n"
+        "  ros2_medkit_gateway vendors cpp-httplib 0.14.3 - ensure ros2_medkit_gateway\n"
+        "  is built first, or pass VENDORED_DIR to medkit_find_cpp_httplib().\n"
         "  See: https://selfpatch.github.io/ros2_medkit/installation.html")
     endif()
   endif()

src/ros2_medkit_cmake/design/index.rst

@@ -38,7 +38,7 @@ The package provides four CMake modules installed to the ament index:
 4. **ROS2MedkitCompat.cmake** - Multi-distro compatibility layer
 
    - ``medkit_find_yaml_cpp()`` - Resolves yaml-cpp across Humble (no cmake target) and Jazzy (namespaced target)
-   - ``medkit_find_cpp_httplib()`` - Finds cpp-httplib via pkg-config (Jazzy/Noble) or cmake config (source build on Humble)
+   - ``medkit_find_cpp_httplib()`` - Finds cpp-httplib >= 0.14 via pkg-config, cmake config, or vendored fallback (``VENDORED_DIR`` param)
    - ``medkit_detect_compat_defs()`` - Detects rclcpp and rosbag2 versions, sets ``MEDKIT_RCLCPP_VERSION_MAJOR`` and ``MEDKIT_ROSBAG2_OLD_TIMESTAMP``
    - ``medkit_apply_compat_defs(target)`` - Applies compile definitions based on detected versions
    - ``medkit_target_dependencies(target ...)`` - Drop-in replacement for ``ament_target_dependencies`` that also works on Rolling (where ``ament_target_dependencies`` was removed)