Overhaul FindBrotli to fix weird issues (#604)

Should get rid of the issue about not being able to create an ALIAS on
MinGW, as well as the "No REQUIRED_VARS" issue.

Fixes #603 (hopefully)

cmake/FindBrotli.cmake

@@ -5,117 +5,132 @@
 # The targets will have the same names, but it will use the static libs.
 #
 # Valid find_package COMPONENTS names: "decoder", "encoder", and "common"
+# Note that if you're requiring "decoder" or "encoder", then "common" will be automatically added as required.
 #
 # Defines the libraries (if found): Brotli::decoder, Brotli::encoder, Brotli::common
 # and the includes path variable: Brotli_INCLUDE_DIR
+#
+# If it's failing to find the libraries, try setting BROTLI_ROOT_DIR to the folder containing your library & include dir.
 
-function(brotli_err_msg _err_msg)
+# If they asked for a specific version, warn/fail since we don't support it.
+# TODO: if they start distributing the version somewhere, implement finding it.
+# But currently there's a version header that doesn't seem to get installed.
+if(Brotli_FIND_VERSION)
+	set(_brotli_version_error_msg "FindBrotli.cmake doesn't have version support!")
 	# If the package is required, throw a fatal error
 	# Otherwise, if not running quietly, we throw a warning
 	if(Brotli_FIND_REQUIRED)
-		message(FATAL_ERROR "${_err_msg}")
+		message(FATAL_ERROR "${_brotli_version_error_msg}")
 	elseif(NOT Brotli_FIND_QUIETLY)
-		message(WARNING "${_err_msg}")
+		message(WARNING "${_brotli_version_error_msg}")
 	endif()
-endfunction()
-
-# If they asked for a specific version, warn/fail since we don't support it.
-if(Brotli_FIND_VERSION)
-	brotli_err_msg("FindBrotli.cmake doesn't have version support!")
 endif()
 
-# Since both decoder & encoder require the common lib (I think), force its requirement..
+# Since both decoder & encoder require the common lib, force its requirement..
 # if the user is requiring either of those other libs.
 if(Brotli_FIND_REQUIRED_decoder OR Brotli_FIND_REQUIRED_encoder)
 	set(Brotli_FIND_REQUIRED_common TRUE)
 endif()
 
+# Support preference of static libs by adjusting CMAKE_FIND_LIBRARY_SUFFIXES
+# Credit to FindOpenSSL.cmake for this
+if(BROTLI_USE_STATIC_LIBS)
+  set(_brotli_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+  if(WIN32)
+    set(CMAKE_FIND_LIBRARY_SUFFIXES .lib .a ${CMAKE_FIND_LIBRARY_SUFFIXES})
+  else()
+    set(CMAKE_FIND_LIBRARY_SUFFIXES .a)
+  endif()
+endif()
+
 # Make PkgConfig optional, since some users (mainly Windows) don't have it.
 # But it's a lot more clean than manually using find_library.
 find_package(PkgConfig QUIET)
-if(PKG_CONFIG_FOUND)
-	if(BROTLI_USE_STATIC_LIBS)
-		# Have to use _STATIC to tell PkgConfig to find the static libs.
-		pkg_check_modules(Brotli_common_STATIC QUIET IMPORTED_TARGET libbrotlicommon)
-		pkg_check_modules(Brotli_decoder_STATIC QUIET IMPORTED_TARGET libbrotlidec)
-		pkg_check_modules(Brotli_encoder_STATIC QUIET IMPORTED_TARGET libbrotlienc)
-	else()
-		pkg_check_modules(Brotli_common QUIET IMPORTED_TARGET libbrotlicommon)
-		pkg_check_modules(Brotli_decoder QUIET IMPORTED_TARGET libbrotlidec)
-		pkg_check_modules(Brotli_encoder QUIET IMPORTED_TARGET libbrotlienc)
-	endif()
-endif()
 
 # Only used if the PkgConfig libraries aren't used.
 find_path(Brotli_INCLUDE_DIR
-	NAMES "brotli/decode.h" "brotli/encode.h"
-	PATH_SUFFIXES "include" "includes"
+	NAMES
+		"brotli/decode.h"
+		"brotli/encode.h"
+	HINTS
+		${BROTLI_ROOT_DIR}
+	PATH_SUFFIXES
+		"include"
+		"includes"
 	DOC "The path to Brotli's include directory."
 )
+# Hides this var from the GUI
+mark_as_advanced(Brotli_INCLUDE_DIR)
 
-# Also check if Brotli_decoder was defined, as it can be passed by the end-user
-if(NOT TARGET PkgConfig::Brotli_decoder AND NOT Brotli_decoder AND NOT TARGET PkgConfig::Brotli_decoder_STATIC)
-	if(BROTLI_USE_STATIC_LIBS)
-		list(APPEND _brotli_decoder_lib_names
-			"brotlidec-static"
-			"libbrotlidec-static"
-		)
-	else()
-		list(APPEND _brotli_decoder_lib_names
-			"brotlidec"
-			"libbrotlidec"
-		)
-	endif()
-	find_library(Brotli_decoder
-		NAMES ${_brotli_decoder_lib_names}
-		PATH_SUFFIXES
-			"lib"
-			"lib64"
-			"libs"
-			"libs64"
-			"lib/x86_64-linux-gnu"
-	)
+# Just used for PkgConfig stuff in the loop below
+set(_brotli_stat_str "")
+if(BROTLI_USE_STATIC_LIBS)
+	set(_brotli_stat_str "_STATIC")
 endif()
 
-# Also check if Brotli_encoder was defined, as it can be passed by the end-user
-if(NOT TARGET PkgConfig::Brotli_encoder AND NOT Brotli_encoder AND NOT TARGET PkgConfig::Brotli_encoder_STATIC)
-	if(BROTLI_USE_STATIC_LIBS)
-		list(APPEND _brotli_encoder_lib_names
-			"brotlienc-static"
-			"libbrotlienc-static"
-		)
-	else()
-		list(APPEND _brotli_encoder_lib_names
-			"brotlienc"
-			"libbrotlienc"
-		)
+# Lets us know we are using the PkgConfig libraries
+# Will be set false if any non-pkgconf vars are used
+set(_brotli_using_pkgconf TRUE)
+
+# Each string here is "ComponentName;LiteralName" (the semi-colon is a delimiter)
+foreach(_listvar "common;common" "decoder;dec" "encoder;enc")
+	# Split the component name and literal library name from the listvar
+	list(GET _listvar 0 _component_name)
+	list(GET _listvar 1 _libname)
+
+	if(PKG_CONFIG_FOUND)
+		# These need to be GLOBAL for MinGW when making ALIAS libraries against them.
+		if(BROTLI_USE_STATIC_LIBS)
+			# Have to use _STATIC to tell PkgConfig to find the static libs.
+			pkg_check_modules(Brotli_${_component_name}_STATIC QUIET GLOBAL IMPORTED_TARGET libbrotli${_libname})
+		else()
+			pkg_check_modules(Brotli_${_component_name} QUIET GLOBAL IMPORTED_TARGET libbrotli${_libname})
+		endif()
+	endif()
+
+	# Check if the target was already found by Pkgconf 
+	if(TARGET PkgConfig::Brotli_${_component_name} OR TARGET PkgConfig::Brotli_${_component_name}_STATIC)
+		# Can't use generators for ALIAS targets, so you get this jank
+		add_library(Brotli::${_component_name} ALIAS PkgConfig::Brotli_${_component_name}${_brotli_stat_str})
+
+		# Tells HANDLE_COMPONENTS we found the component
+		set(Brotli_${_component_name}_FOUND TRUE)
+		if(Brotli_FIND_REQUIRED_${_component_name})
+			# If the lib is required, we can add its literal path as a required var for FindPackageHandleStandardArgs
+			# Since it won't accept the PkgConfig targets
+			if(BROTLI_USE_STATIC_LIBS)
+				list(APPEND _brotli_req_vars "Brotli_${_component_name}_STATIC_LIBRARIES")
+			else()
+				list(APPEND _brotli_req_vars "Brotli_${_component_name}_LINK_LIBRARIES")
+			endif()
+		endif()
+
+		# Skip searching for the libs with find_library since it was already found by Pkgconf
+		continue()
+	endif()
+
+	# Lets us know we aren't using the PkgConfig libraries
+	set(_brotli_using_pkgconf FALSE)
+	if(Brotli_FIND_REQUIRED_${_component_name})
+		# If it's required, we can set the name used in find_library as a required var for FindPackageHandleStandardArgs
+		list(APPEND _brotli_req_vars "Brotli_${_component_name}")
 	endif()
-	find_library(Brotli_encoder
-		NAMES ${_brotli_encoder_lib_names}
-		PATH_SUFFIXES
-			"lib"
-			"lib64"
-			"libs"
-			"libs64"
-			"lib/x86_64-linux-gnu"
-	)
-endif()
 
-# Also check if Brotli_common was defined, as it can be passed by the end-user
-if(NOT TARGET PkgConfig::Brotli_common AND NOT Brotli_common AND NOT TARGET PkgConfig::Brotli_common_STATIC)
 	if(BROTLI_USE_STATIC_LIBS)
-		list(APPEND _brotli_common_lib_names
-			"brotlicommon-static"
-			"libbrotlicommon-static"
+		list(APPEND _brotli_lib_names
+			"brotli${_libname}-static"
+			"libbrotli${_libname}-static"
 		)
 	else()
-		list(APPEND _brotli_common_lib_names
-			"brotlicommon"
-			"libbrotlicommon"
+		list(APPEND _brotli_lib_names
+			"brotli${_libname}"
+			"libbrotli${_libname}"
 		)
 	endif()
-	find_library(Brotli_common
-		NAMES ${_brotli_common_lib_names}
+
+	find_library(Brotli_${_component_name}
+		NAMES ${_brotli_lib_names}
+		HINTS ${BROTLI_ROOT_DIR}
 		PATH_SUFFIXES
 			"lib"
 			"lib64"
@@ -123,73 +138,41 @@ if(NOT TARGET PkgConfig::Brotli_common AND NOT Brotli_common AND NOT TARGET PkgC
 			"libs64"
 			"lib/x86_64-linux-gnu"
 	)
-endif()
+	# Hide the library variable from the Cmake GUI
+	mark_as_advanced(Brotli_${_component_name})
 
-set(_brotli_req_vars "")
-# Generic loop to either create all the aliases for the end-user, or throw errors/warnings.
-# Note that the case here needs to match the case we used elsewhere in this file.
-foreach(_target_name "common" "decoder" "encoder")
-	# The PkgConfig IMPORTED_TARGET has PkgConfig:: prefixed to it.
-	if(TARGET PkgConfig::Brotli_${_target_name} OR TARGET PkgConfig::Brotli_${_target_name}_STATIC)
-		set(_stat_str "")
-		if(BROTLI_USE_STATIC_LIBS)
-			set(_stat_str "_STATIC")
-		endif()
-		# Can't use generators for ALIAS targets, so you get this jank
-		add_library(Brotli::${_target_name} ALIAS PkgConfig::Brotli_${_target_name}${_stat_str})
+	# Unset since otherwise it'll stick around for the next loop and break things
+	unset(_brotli_lib_names)
 
-			# The PkgConfig version of the library has a slightly different path to its lib.
-		if(Brotli_FIND_REQUIRED_${_target_name})
-			if(BROTLI_USE_STATIC_LIBS)
-				list(APPEND _brotli_req_vars "Brotli_${_target_name}_STATIC_LIBRARIES")
-			else()
-				list(APPEND _brotli_req_vars "Brotli_${_target_name}_LINK_LIBRARIES")
-			endif()
-		endif()
-	# This will only trigger for libraries we found using find_library
-	elseif(Brotli_${_target_name})
-		add_library("Brotli::${_target_name}" UNKNOWN IMPORTED)
-		# Safety-check the includes dir
-		if(NOT Brotli_INCLUDE_DIR)
-			brotli_err_msg("Failed to find Brotli's includes directory. Try manually defining \"Brotli_INCLUDE_DIR\" to Brotli's header path on your system.")
-		endif()
+	# Check if find_library found the library
+	if(Brotli_${_component_name})
+		# Tells HANDLE_COMPONENTS we found the component
+		set(Brotli_${_component_name}_FOUND TRUE)
+
+		add_library("Brotli::${_component_name}" UNKNOWN IMPORTED)
 		# Attach the literal library and include dir to the IMPORTED target for the end-user
-		set_target_properties("Brotli::${_target_name}" PROPERTIES
+		set_target_properties("Brotli::${_component_name}" PROPERTIES
 			INTERFACE_INCLUDE_DIRECTORIES "${Brotli_INCLUDE_DIR}"
-			IMPORTED_LOCATION "${Brotli_${_target_name}}"
+			IMPORTED_LOCATION "${Brotli_${_component_name}}"
 		)
-		# Attach the library from find_library to our required vars (if it's required)
-		if(Brotli_FIND_REQUIRED_${_target_name})
-			list(APPEND _brotli_req_vars "Brotli_${_target_name}")
-		endif()
-	# This will only happen if it's a required library but we didn't find it.
-	elseif(Brotli_FIND_REQUIRED_${_target_name})
-		# Only bother with an error/failure if they actually required the lib.
-		brotli_err_msg("Failed to find Brotli's ${_target_name} library. Try manually defining \"Brotli_${_target_name}\" to its path on your system.")
-		# If the compnent was required but not found, you set XXX_FOUND to false to signify failure to find component(s)
-		# This is used in find_package_handle_standard_args's HANDLE_COMPONENTS (I think)
-		set(Brotli_FOUND FALSE)
+	else()
+		# Tells HANDLE_COMPONENTS we found the component
+		set(Brotli_${_component_name}_FOUND FALSE)
 	endif()
 endforeach()
 
 include(FindPackageHandleStandardArgs)
+# Sets Brotli_FOUND, and fails the find_package(Brotli) call if it was REQUIRED but missing libs.
 find_package_handle_standard_args(Brotli
-	FOUND_VAR Brotli_FOUND
-	REQUIRED_VARS ${_brotli_req_vars}
+	FOUND_VAR
+		Brotli_FOUND
+	REQUIRED_VARS
+		Brotli_INCLUDE_DIR
+		${_brotli_required_targets}
 	HANDLE_COMPONENTS
 )
 
-if(Brotli_FOUND)
-	include(FindPackageMessage)
-	foreach(_lib_name ${_brotli_req_vars})
-		# TODO: remove this if/when The Cmake PkgConfig file fixes the non-quiet message about libbrotlicommon being found.
-		if(${_lib_name} MATCHES "common")
-			# This avoids a duplicate "Found Brotli: /usr/lib/libbrotlicommon.so" type message.
-			continue()
-		endif()
-		# Double-expand the var to get the actual path instead of the variable's name.
-		find_package_message(Brotli "Found Brotli: ${${_lib_name}}"
-			"[${${_lib_name}}][${Brotli_INCLUDE_DIR}]"
-		)
-	endforeach()
+# Restore the original find library ordering
+if(BROTLI_USE_STATIC_LIBS)
+  set(CMAKE_FIND_LIBRARY_SUFFIXES ${_brotli_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES})
 endif()