cmake: fix feature availability reporting

Some detected libraries were not reported when a feature is disabled.
This change removes unnecessary second find_package calls and sets
HAVE_xxx immediately based on xxx_FOUND.

CMakeLists.txt

@@ -57,7 +57,8 @@ else()
 endif()
 find_package(Jansson  2.5   QUIET)
 set(ENABLE_HPACK_TOOLS_DEFAULT ${JANSSON_FOUND})
-find_package(Libevent 2.0.8 QUIET COMPONENTS openssl)
+# 2.0.8 is required because we use evconnlistener_set_error_cb()
+find_package(Libevent 2.0.8 QUIET COMPONENTS libevent openssl)
 set(ENABLE_EXAMPLES_DEFAULT ${LIBEVENT_OPENSSL_FOUND})
 find_package(Cython         QUIET)
 find_package(PythonLibs     QUIET)
@@ -67,7 +68,7 @@ else()
   set(ENABLE_PYTHON_BINDINGS_DEFAULT OFF)
 endif()
 
-find_package(LibXml2        QUIET)
+find_package(LibXml2 2.7.7  QUIET)
 set(WITH_LIBXML2_DEFAULT    ${LIBXML2_FOUND})
 find_package(Jemalloc       QUIET)
 set(WITH_JEMALLOC_DEFAULT   ${JEMALLOC_FOUND})
@@ -76,6 +77,13 @@ set(WITH_SPDYLAY_DEFAULT    ${SPDYLAY_FOUND})
 
 include(CMakeOptions.txt)
 
+if(ENABLE_LIB_ONLY AND (ENABLE_APP OR ENABLE_HPACK_TOOLS OR ENABLE_EXAMPLES OR
+  ENABLE_PYTHON_BINDINGS))
+  # Remember when disabled options are disabled for later diagnostics.
+  set(ENABLE_LIB_ONLY_DISABLED_OTHERS 1)
+else()
+  set(ENABLE_LIB_ONLY_DISABLED_OTHERS 0)
+endif()
 if(ENABLE_LIB_ONLY)
   set(ENABLE_APP            OFF)
   set(ENABLE_HPACK_TOOLS    OFF)
@@ -130,10 +138,12 @@ cmake_pop_check_state()
 set(APP_LIBRARIES)
 
 if(ENABLE_PYTHON_BINDINGS)
-  find_package(Cython         REQUIRED)
-  find_package(PythonLibs     REQUIRED)
+  if(NOT (CYTHON_FOUND AND PYTHONLIBS_FOUND))
+    message(FATAL_ERROR "python bindings were requested "
+      "(ENABLE_PYTHON_BINDINGS=1) but dependencies are not met.")
+  endif()
   if(NOT PYTHON_VERSION_STRING STREQUAL PYTHONLIBS_VERSION_STRING)
-    message(SEND_ERROR
+    message(FATAL_ERROR
       "Python executable and library must have the same version!"
       " Found Python ${PYTHON_VERSION_STRING} and"
       " PythonLibs ${PYTHONLIBS_VERSION_STRING}"
@@ -158,83 +168,30 @@ endif()
 # APP_LIBRARIES if it is really specific to OpenSSL?
 
 find_package(CUnit 2.1)
-if(CUNIT_FOUND)
-  enable_testing()
-  set(HAVE_CUNIT 1)
-else()
-  set(HAVE_CUNIT 0)
-endif()
-
-if(ENABLE_APP)
-  find_package(OpenSSL 1.0.1 REQUIRED)
-  find_package(Libev 4.15 REQUIRED)
-  find_package(ZLIB 1.2.3 REQUIRED)
-endif()
+enable_testing()
+set(HAVE_CUNIT      ${CUNIT_FOUND})
 
 # openssl (for src)
+set(HAVE_OPENSSL    ${OPENSSL_FOUND})
 if(OPENSSL_FOUND)
-  set(HAVE_OPENSSL 1)
   set(OPENSSL_INCLUDE_DIRS ${OPENSSL_INCLUDE_DIR})
-else()
-  set(HAVE_OPENSSL 0)
 endif()
 # libev (for src)
-if(LIBEV_FOUND)
-  set(HAVE_LIBEV 1)
-else()
-  set(HAVE_LIBEV 0)
-endif()
-if(ZLIB_FOUND)
-  set(HAVE_ZLIB 1)
-else()
-  set(HAVE_ZLIB 0)
-endif()
-
-if(ENABLE_EXAMPLES)
-  # libevent_openssl (for examples)
-  # 2.0.8 is required because we use evconnlistener_set_error_cb()
-  find_package(Libevent 2.0.8 REQUIRED COMPONENTS libevent openssl)
+set(HAVE_LIBEV      ${LIBEV_FOUND})
+set(HAVE_ZLIB       ${ZLIB_FOUND})
+set(HAVE_LIBEVENT_OPENSSL ${LIBEVENT_FOUND})
+if(LIBEVENT_FOUND)
+  # Must both link the core and openssl libraries.
   set(LIBEVENT_OPENSSL_LIBRARIES ${LIBEVENT_LIBRARIES})
-  set(HAVE_LIBEVENT_OPENSSL 1)
-else()
-  set(HAVE_LIBEVENT_OPENSSL 0)
-endif()
-
-if(ENABLE_HPACK_TOOLS)
-  # jansson (for src/nghttp, src/deflatehd and src/inflatehd)
-  find_package(Jansson 2.5 REQUIRED)
-  set(HAVE_JANSSON 1)
-else()
-  set(HAVE_JANSSON 0)
 endif()
-
+# jansson (for src/nghttp, src/deflatehd and src/inflatehd)
+set(HAVE_JANSSON    ${JANSSON_FOUND})
 # libxml2 (for src/nghttp)
-if(WITH_LIBXML2)
-  find_package(LibXml2 2.7.7 REQUIRED)
-  set(HAVE_LIBXML2 1)
-else()
-  set(HAVE_LIBXML2 0)
-endif()
-
+set(HAVE_LIBXML2    ${LIBXML2_FOUND})
 # jemalloc
-if(WITH_JEMALLOC)
-  find_package(Jemalloc REQUIRED)
-  if(JEMALLOC_FOUND)
-    set(HAVE_JEMALLOC 1)
-  else()
-    set(HAVE_JEMALLOC 0)
-  endif()
-else()
-  set(HAVE_JEMALLOC 0)
-endif()
-
+set(HAVE_JEMALLOC   ${JEMALLOC_FOUND})
 # spdylay (for src/nghttpx and src/h2load)
-if(WITH_SPDYLAY)
-  find_package(Spdylay 1.3.2 REQUIRED)
-  set(HAVE_SPDYLAY 1)
-else()
-  set(HAVE_SPDYLAY 0)
-endif()
+set(HAVE_SPDYLAY    ${SPDYLAY_FOUND})
 
 if(ENABLE_ASIO_LIB)
   find_package(Boost 1.54.0 REQUIRED system thread)
@@ -259,19 +216,8 @@ endif()
 if(ENABLE_EXAMPLES OR ENABLE_APP OR ENABLE_HPACK_TOOLS OR ENABLE_ASIO_LIB)
   set(ENABLE_THIRD_PARTY 1)
   # mruby (for src/nghttpx)
-  if(WITH_MRUBY)
-    set(HAVE_MRUBY 1)
-    set(MRUBY_LIBRARY
-      "${CMAKE_BINARY_DIR}/third-party/mruby/build/lib/${CMAKE_STATIC_LIBRARY_PREFIX}mruby${CMAKE_STATIC_LIBRARY_SUFFIX}"
-    )
-  else()
-    set(HAVE_MRUBY 0)
-  endif()
-  if(WITH_NEVERBLEED)
-    set(HAVE_NEVERBLEED 1)
-  else()
-    set(HAVE_NEVERBLEED 0)
-  endif()
+  set(HAVE_MRUBY      ${WITH_MRUBY})
+  set(HAVE_NEVERBLEED ${WITH_NEVERBLEED})
 else()
   set(HAVE_MRUBY 0)
   set(HAVE_NEVERBLEED 0)
@@ -533,3 +479,7 @@ message(STATUS "summary of build options:
       Python bindings:${ENABLE_PYTHON_BINDINGS}
       Threading:      ${ENABLE_THREADS}
 ")
+if(ENABLE_LIB_ONLY_DISABLED_OTHERS)
+  message("Only the library will be built. To build other components "
+    "(such as applications and examples), set ENABLE_LIB_ONLY=OFF.")
+endif()