Refactor pkg-config generation to use target properties

This change uses target properties to fill in the slots in the
generated pkg-config files. Previously this was unstructured strings
and flag juggling.

Author: vector-of-bool

build/cmake/ResSearch.cmake

@@ -1,10 +1,12 @@
 include(CheckSymbolExists)
 
-set(resolve_libs)
+# The name of the library that performs name resolution, suitable for giving to the "-l" link flag
+set(RESOLVE_LIB_NAME)
+# If TRUE, then the C runtime provides the name resolution that we need
 set(resolve_is_libc FALSE)
 
 if(WIN32)
-    set(resolve_libs Dnsapi)
+    set(RESOLVE_LIB_NAME Dnsapi)
     set(_MONGOC_HAVE_DNSAPI 1)
 else()
     # Thread-safe DNS query function for _mongoc_client_get_srv.
@@ -14,7 +16,7 @@ else()
     check_symbol_exists(res_nclose resolv.h _MONGOC_HAVE_RES_NCLOSE)
     if(MONGOC_HAVE_RES_NSEARCH)
         # We have res_nsearch. Call res_ndestroy (BSD/Mac) or res_nclose (Linux)?
-        set(resolve_libs resolv)
+        set(RESOLVE_LIB_NAME resolv)
     elseif(CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
         # On FreeBSD, the following line does not properly detect res_search,
         # which is included in libc on FreeBSD:
@@ -32,7 +34,7 @@ else()
         # Thread-unsafe function.
         check_symbol_exists(res_search resolv.h _MONGOC_HAVE_RES_SEARCH)
         if(_MONGOC_HAVE_RES_SEARCH)
-            set(resolve_libs resolv)
+            set(RESOLVE_LIB_NAME resolv)
         endif()
     endif()
 endif()
@@ -43,11 +45,12 @@ _mongo_pick(MONGOC_HAVE_RES_NDESTROY 1 0 _MONGOC_HAVE_RES_NDESTROY)
 _mongo_pick(MONGOC_HAVE_RES_NCLOSE 1 0 _MONGOC_HAVE_RES_NCLOSE)
 _mongo_pick(MONGOC_HAVE_RES_SEARCH 1 0 _MONGOC_HAVE_RES_SEARCH)
 
-if(resolve_libs OR resolve_is_libc)
+if(RESOLVE_LIB_NAME OR resolve_is_libc)
     # Define the resolver interface:
     add_library(_mongoc-resolve INTERFACE)
-    target_link_libraries(_mongoc-resolve INTERFACE ${resolve_libs})
-    add_library(mongo::c::detail::resolve ALIAS _mongoc-resolve)
-    set_property(TARGET _mongoc-resolve PROPERTY EXPORT_NAME c::detail::resolve)
+    add_library(mongo::detail::c_resolve ALIAS _mongoc-resolve)
+    set_target_properties(_mongoc-resolve PROPERTIES
+        INTERFACE_LINK_LIBRARIES "${RESOLVE_LIB_NAME}"
+        EXPORT_NAME detail::c_resolve)
     install(TARGETS _mongoc-resolve EXPORT mongoc-targets)
 endif()

src/libmongoc/CMakeLists.txt

@@ -720,10 +720,10 @@ set_property(TARGET _mongoc-dependencies PROPERTY EXPORT_NAME dependencies)
 
 if(ENABLE_SRV)
    # Interface target defined by ResSearch.cmake:
-   if(NOT TARGET mongo::c::detail::resolve)
+   if(NOT TARGET mongo::detail::c_resolve)
       message(SEND_ERROR "ENABLE_SRV is “${ENABLE_SRV}”, but we were unable to find a name resolution library")
    endif()
-   target_link_libraries(_mongoc-dependencies INTERFACE mongo::c::detail::resolve)
+   target_link_libraries(_mongoc-dependencies INTERFACE mongo::detail::c_resolve)
 endif()
 
 if (WIN32)
@@ -786,8 +786,12 @@ target_include_directories (
       $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/../../src/common>
 )
 
-set_target_properties (mongoc_shared PROPERTIES VERSION 0.0.0 SOVERSION 0)
-set_target_properties (mongoc_shared PROPERTIES OUTPUT_NAME "${MONGOC_OUTPUT_BASENAME}-${MONGOC_API_VERSION}")
+set_target_properties (mongoc_shared PROPERTIES
+   OUTPUT_NAME "${MONGOC_OUTPUT_BASENAME}-${MONGOC_API_VERSION}"
+   VERSION 0.0.0
+   SOVERSION 0
+   pc_REQUIRES "libbson-1.0"
+   )
 
 if (MONGOC_ENABLE_STATIC_BUILD)
    add_library (mongoc_static STATIC ${SOURCES} ${HEADERS} ${HEADERS_FORWARDING})
@@ -800,6 +804,10 @@ if (MONGOC_ENABLE_STATIC_BUILD)
       target_compile_options (mongoc_static PUBLIC -fPIC)
       message (STATUS "Adding -fPIC to compilation of mongoc_static components")
    endif ()
+   if(ENABLE_SRV AND RESOLVE_LIB_NAME)
+      # The static library needs to link to the resolver in pkg-config:
+      set_property(TARGET mongoc_static APPEND PROPERTY pc_LIBS "-l${RESOLVE_LIB_NAME}")
+   endif()
    target_include_directories (mongoc_static PRIVATE ${ZLIB_INCLUDE_DIRS})
    target_include_directories (mongoc_static PRIVATE ${LIBMONGOCRYPT_INCLUDE_DIRECTORIES})
    if (MONGOC_ENABLE_MONGODB_AWS_AUTH)
@@ -827,8 +835,11 @@ if (MONGOC_ENABLE_STATIC_BUILD)
          $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/../../src>
          $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/../../src/common>
    )
-   set_target_properties (mongoc_static PROPERTIES VERSION 0.0.0)
-   set_target_properties (mongoc_static PROPERTIES OUTPUT_NAME "${MONGOC_OUTPUT_BASENAME}-static-${MONGOC_API_VERSION}")
+   set_target_properties (mongoc_static PROPERTIES
+      VERSION 0.0.0
+      OUTPUT_NAME "${MONGOC_OUTPUT_BASENAME}-static-${MONGOC_API_VERSION}"
+      pc_REQUIRES "libbson-static-1.0"
+      )
 endif ()
 
 if (ENABLE_APPLE_FRAMEWORK)
@@ -1193,44 +1204,109 @@ set (VERSION "${MONGOC_VERSION}")
 set (prefix "${CMAKE_INSTALL_PREFIX}")
 set (libdir "\${prefix}/${CMAKE_INSTALL_LIBDIR}")
 
-foreach (
-      FLAG
-      ${SASL_LIBRARIES} ${SSL_LIBRARIES} ${SHM_LIBRARIES}
-      ${THREAD_LIB} ${ZLIB_LIBRARIES} ${SNAPPY_LIBRARIES} ${MONGOC_ZSTD_LIBRARIES} ${ICU_LIBRARIES}
+# Collect link items for the static library to be inserted into the pkg-config
+if(TARGET mongoc_static)
+   set(link_options
+      ${SASL_LIBRARIES} ${SSL_LIBRARIES} ${SHM_LIBRARIES} ${THREAD_LIB} ${ZLIB_LIBRARIES}
+      ${SNAPPY_LIBRARIES} ${MONGOC_ZSTD_LIBRARIES} ${ICU_LIBRARIES}
       ${LIBMONGOCRYPT_LIBRARY})
+   # Replace all absolute paths with search-dir link-file options:
+   list(TRANSFORM link_options
+        REPLACE "^(.+)/lib([^/]+)\\.[a-z]+$"
+                "-L\\1;-l\\2"
+        REGEX "^/")
+   # Prepend "-l" to all bare names:
+   list(TRANSFORM link_options PREPEND "-l" REGEX "^[^-]")
+   list(REMOVE_DUPLICATES link_options)
+   message(DEBUG "Computed static library link options: ${link_options}")
+   set_property(TARGET mongoc_static APPEND PROPERTY pc_LIBS ${link_options})
+endif()
 
-   if (IS_ABSOLUTE "${FLAG}")
-      get_filename_component (FLAG_DIR "${FLAG}" DIRECTORY)
-      get_filename_component (FLAG_FILE "${FLAG}" NAME_WE)
-      STRING (REGEX REPLACE "^lib" "" FLAG_FILE "${FLAG_FILE}")
-      set (MONGOC_LIBRARIES "${MONGOC_LIBRARIES} -L${FLAG_DIR} -l${FLAG_FILE}")
-   elseif (FLAG MATCHES "^-.*")
-      # Flag starts with dash, add it as-is.
-      set (MONGOC_LIBRARIES "${MONGOC_LIBRARIES} ${FLAG}")
-   else ()
-      # Flag doesn't start with dash, add it with a dash.
-      set (MONGOC_LIBRARIES "${MONGOC_LIBRARIES} -l${FLAG}")
-   endif ()
-endforeach ()
+# More pkg-config properties:
+set_target_properties(${TARGETS_TO_INSTALL} PROPERTIES
+   pc_NAME "libmongoc"
+   pc_DESCRIPTION "The libmongoc MongoDB client library."
+   pc_VERSION "${VERSION}")
+# Relative include-path will be given the install prefix:
+set_property(TARGET ${TARGETS_TO_INSTALL} APPEND PROPERTY pc_INCLUDE_DIRECTORIES "${MONGOC_HEADER_INSTALL_DIR}")
+
+#[[
+Utility for configuring a file and then evaluating generator expressions on it.
+The content of the file has a tiny templating DSL for writing generator
+expressions. Expansion takes place as follows:
+   1. Delete any content starting at hash-tilde "#~" until the next newline
+   2. Search for any lines of the form "%define foo bar". For each instance,
+      replace "foo" with "bar" in the remainder of the file. The "% foo bar"
+      line is deleted.
+   3. If a tilde "~" appears adjacent to any of "$,<:>@", delete the tilde and
+      all adjacent whitespace.
+   4. Run string(CONFIGURE ... @ONLY) on the result to replace variable
+      references. Special replacements @space@, @newline, and @empty@ are also
+      available for adjusting whitespace after ~ trimming.
+   5. Run file(GENERATE).
+]]
+function(_mongoc_configure_and_generate_file input output)
+   set(CMAKE_MESSAGE_CONTEXT _mongoc_configure_and_generate_file)
+   # If given a relative input path, make it relative to the current source dir:
+   get_filename_component(abs_in "${input}" ABSOLUTE)
+   file(READ "${input}" content)
+   # Some convenience values for @expansion@ in the file:
+   set(space " ")
+   set(newline "\n")
+   set(empty "")
+   # Delete "#~" comments:
+   string(REGEX REPLACE "#~[^\n]*" "" content "${content}")
+   # Replace our simple "%define <name> <value>" macros:
+   while(content MATCHES "(.*)\n *%define *([a-zA-Z_\\$<>:-]+) *([^\n]*)\n(.*)")
+      set(before "${CMAKE_MATCH_1}")
+      set(after "${CMAKE_MATCH_4}")
+      set(def "${CMAKE_MATCH_2}")
+      set(val "${CMAKE_MATCH_3}")
+      message(TRACE "Replace “${def}” with “${val}”")
+      # Only perform the replacment on the remainder of the file following that
+      # line:
+      string(REPLACE "${def}" "${val}" after "${after}")
+      # Splice the results:
+      set(content "${before}\n${after}")
+   endwhile()
+   # Whitespace trimming. right-trim when tilde is to the right of special chars:
+   string(REGEX REPLACE "([,><:@])~[ \n\t]*" "\\1" content "${content}")
+   # Same thing, but on the left-hand side:
+   string(REGEX REPLACE "[ \n\t]*~([^ \t\n])" "\\1" content "${content}")
+   # Replace @varables@:
+   string(CONFIGURE "${content}" content @ONLY)
+   # If given a relative output path, make it relative to the current binary dir:
+   if(NOT IS_ABSOLUTE "${output}")
+      get_filename_component(output "${CMAKE_CURRENT_BINARY_DIR}/${output}" ABSOLUTE)
+   endif()
+   message(DEBUG "Configure+generate file [${input}] -> [${output}]")
+   message(TRACE "Content:\n${content}")
+   # Generate it:
+   file(GENERATE OUTPUT "${output}" CONTENT "${content}" ${ARGN})
+endfunction()
+
+# Generate pkg-config for mongoc_shared
+if(TARGET mongoc_shared)
+   set(GENERATE_TARGET mongoc_shared)
+   _mongoc_configure_and_generate_file(
+      src/libmongoc.pc.in
+      src/libmongoc-1.0.pc)
+   install(FILES ${CMAKE_CURRENT_BINARY_DIR}/src/libmongoc-1.0.pc
+           DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
+endif()
+
+# Now one for mongoc_static:
+if(TARGET mongoc_static)
+   set(GENERATE_TARGET mongoc_static)
+   _mongoc_configure_and_generate_file(
+      src/libmongoc.pc.in
+      src/libmongoc-static-1.0.pc)
+   if(MONGOC_ENABLE_STATIC_INSTALL)
+      install(FILES ${CMAKE_CURRENT_BINARY_DIR}/src/libmongoc-static-1.0.pc
+              DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
+   endif()
+endif()
 
-configure_file (
-   ${CMAKE_CURRENT_SOURCE_DIR}/src/libmongoc-1.0.pc.in
-   ${CMAKE_CURRENT_BINARY_DIR}/src/libmongoc-1.0.pc
-@ONLY)
-install (
-   FILES ${CMAKE_CURRENT_BINARY_DIR}/src/libmongoc-1.0.pc
-   DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig
-)
-if (MONGOC_ENABLE_STATIC_INSTALL)
-   configure_file (
-      ${CMAKE_CURRENT_SOURCE_DIR}/src/libmongoc-static-1.0.pc.in
-      ${CMAKE_CURRENT_BINARY_DIR}/src/libmongoc-static-1.0.pc
-   @ONLY)
-   install (
-      FILES ${CMAKE_CURRENT_BINARY_DIR}/src/libmongoc-static-1.0.pc
-      DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig
-   )
-endif ()
 # Deprecated alias for libmongoc-1.0.pc, see CDRIVER-2086.
 if (MONGOC_ENABLE_SSL)
    configure_file (

src/libmongoc/src/CMakeLists.txt

@@ -2,9 +2,8 @@ add_subdirectory (mongoc)
 
 set_local_dist (src_libmongoc_src_DIST_local
    CMakeLists.txt
-   libmongoc-1.0.pc.in
+   libmongoc.pc.in
    libmongoc-ssl-1.0.pc.in
-   libmongoc-static-1.0.pc.in
    mongoc-config.cmake
 )
 

src/libmongoc/src/libmongoc-1.0.pc.in

@@ -0,0 +1,63 @@
+prefix=@prefix@
+exec_prefix=${prefix}
+libdir=@libdir@
+includedir=${exec_prefix}/include
+
+Name: $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_NAME>
+Description: $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_DESCRIPTION>
+Version: $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_VERSION>
+
+%define $<is-empty: $<STREQUAL:@empty@,
+%define $<<not-empty: $<NOT:$<is-empty:
+
+#~ "Requires" dependencies:
+%define requires_joiner @newline@~ Requires: ~@space@
+%define requires_prop $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_REQUIRES>
+#~ Conditional: Only expand a first "\nRequires: " if Requires is non-empty:
+%define has_requires $<<not-empty:requires_prop>>
+~$<has_requires:requires_joiner>
+#~ The rest:
+~$<JOIN:requires_prop,requires_joiner>
+
+~@newline@~
+
+#~ Link options:
+Libs: -L${libdir} -l$<TARGET_PROPERTY:@GENERATE_TARGET@,OUTPUT_NAME> ~@space@~
+    #~ Join each "Libs" item with spaces. This could be more robust, but it suites our purposes:
+    %define libs_prop $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_LIBS>
+    #~ Remove duplicate items, which will usually be redundant link paths:
+    %define libs $<REMOVE_DUPLICATES:libs_prop>
+    $<JOIN:libs,@space@>~
+
+    #~ Add link options. Don't remove duplicates, because they may be important
+    %define link_opts $<TARGET_PROPERTY:@GENERATE_TARGET@,INTERFACE_LINK_OPTIONS>
+    $<$<<not-empty:link_opts>>:@space@$<JOIN:link_opts,@space@>>
+
+~@newline@~
+
+#~ Compile-flags:
+%define cflags_prop $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_CFLAGS>
+Cflags: $<JOIN:cflags_prop,@space@> ~@space@~
+
+    #~ Options:
+    %define opts_prop $<TARGET_PROPERTY:@GENERATE_TARGET@,INTERFACE_COMPILE_OPTIONS>
+    %define opts $<REMOVE_DUPLICATES:opts_prop>
+    $<JOIN:opts,@space@>~
+
+    #~ Preprocessor definitions:
+    %define defs_prop $<TARGET_PROPERTY:@GENERATE_TARGET@,INTERFACE_COMPILE_DEFINITIONS>
+    %define defs $<REMOVE_DUPLICATES:defs_prop>
+    $<$<<not-empty:defs>>: -D>~
+              $<JOIN:defs, -D>~
+
+    #~ Inclusions:
+    %define inc_prop $<TARGET_PROPERTY:@GENERATE_TARGET@,pc_INCLUDE_DIRECTORIES>
+    %define incs $<REMOVE_DUPLICATES:inc_prop>
+    #~ Absolute path includes are kept absolute:
+    %define abs_includes $<FILTER:incs,INCLUDE,^/>
+    $<$<<not-empty:abs_includes>>: -I>~
+              $<JOIN:abs_includes, -I>~
+    #~ Relative includes are made relative to ${prefix}
+    %define relative_includes $<FILTER:incs,EXCLUDE,^/>
+    $<$<<not-empty:relative_includes>>: -I${prefix}/>~
+              $<JOIN:relative_includes, -I${prefix}/>