corrosion_install: fix reconfiguring breaking EXPORTs (#555)

* corrosion_install: Move error checking into outer scope

It seems this was accidentally put on the check for a
`TARGET ${TARGET_NAME}-static` lib instead of the
`TARGET_TYPE STREQUAL *`

* corrosion_install: Add guard and use CMAKE_CURRENT_BINARY_DIR

It seems something has been switched up and it's using CMAKE_BINARY_DIR
instead of CMAKE_CURRENT_BINARY_DIR.

Additionally, without a guard CMake will write the static/shared
definitions on every reconfigure, making the config file fail.

* corrosion_install: Require EXPORT_NAME to be unique.

Switch back to CMAKE_BINARY_DIR as documented by the function signature.
If we anyway require a globally unique EXPORT_NAME,
then we don't need to use the current binary dir, making the file easier to find.

---------

Co-authored-by: Gtker <[email protected]>
Co-authored-by: Jonathan Schwender <[email protected]>

cmake/Corrosion.cmake

@@ -1101,15 +1101,16 @@ ANCHOR: corrosion-install
   and is not officially released yet. Feedback and Suggestions are welcome.
 
 ```cmake
-corrosion_install(TARGETS <target1> ... <targetN> [EXPORT <export-name]
+corrosion_install(TARGETS <target1> ... <targetN> [EXPORT <export-name>]
                   [[ARCHIVE|LIBRARY|RUNTIME|PUBLIC_HEADER]
                    [DESTINATION <dir>]
                    [PERMISSIONS <permissions...>]
                    [CONFIGURATIONS [Debug|Release|<other-configuration>]]
                   ] [...])
 ```
 * **TARGETS**: Target or targets to install.
-* **EXPORT**: Creates an export that can be installed with `install(EXPORT)`. Also creates a file at ${CMAKE_BINARY_DIR}/corrosion/<export-name>Corrosion.cmake that must be included in the installed config file.
+* **EXPORT**: Creates an export that can be installed with `install(EXPORT)`. <export-name> must be globally unique.
+             Also creates a file at ${CMAKE_BINARY_DIR}/corrosion/<export-name>Corrosion.cmake that must be included in the installed config file.
 * **ARCHIVE**/**LIBRARY**/**RUNTIME**/PUBLIC_HEADER: Designates that the following settings only apply to that specific type of object.
 * **DESTINATION**: The subdirectory within the CMAKE_INSTALL_PREFIX that a specific object should be placed. Defaults to values from GNUInstallDirs.
 * **PERMISSIONS**: The permissions of files copied into the install prefix.
@@ -1169,6 +1170,10 @@ function(corrosion_install)
                 list(REMOVE_AT ARGN 0) # Pop <export-name>
                 set(EXTRA_TARGETS_EXPORT_NAME ${EXPORT_NAME}Corrosion.cmake)
                 set(EXPORT_NAME EXPORT ${EXPORT_NAME})
+                set(EXPORT_FILE_PATH "${CMAKE_BINARY_DIR}/corrosion/${EXTRA_TARGETS_EXPORT_NAME}")
+                # Remove first, since otherwise we will append to the file on every reconfigure.
+                # Assumes that the corrosion_install will only be called once for a given EXPORT_NAME.
+                file(REMOVE "${EXPORT_FILE_PATH}")
             endif()
         else()
             # Prevent variable set in user code from interfering
@@ -1308,8 +1313,7 @@ function(corrosion_install)
 
                     if(EXPORT_NAME)
                         get_target_property(COR_FILE_NAME ${INSTALL_TARGET}-static COR_FILE_NAME)
-                        file(APPEND
-                            ${CMAKE_BINARY_DIR}/corrosion/${EXTRA_TARGETS_EXPORT_NAME}
+                        file(APPEND "${EXPORT_FILE_PATH}"
 "
 add_library(${INSTALL_TARGET}-static STATIC IMPORTED)
 set_target_properties(${INSTALL_TARGET}-static
@@ -1319,8 +1323,6 @@ set_target_properties(${INSTALL_TARGET}-static
 "
                         )
                     endif()
-                else()
-                    message(FATAL_ERROR "Unknown target type ${TARGET_TYPE} for install target ${INSTALL_TARGET}")
                 endif()
 
                 if(TARGET ${INSTALL_TARGET}-shared)
@@ -1360,30 +1362,30 @@ set_target_properties(${INSTALL_TARGET}-static
 
                     if(EXPORT_NAME)
                         get_target_property(COR_FILE_NAME ${INSTALL_TARGET}-shared COR_FILE_NAME)
-                        file(APPEND
-                                ${CMAKE_BINARY_DIR}/corrosion/${EXTRA_TARGETS_EXPORT_NAME}
-                                "
+                        file(APPEND "${EXPORT_FILE_PATH}"
+"
 add_library(${INSTALL_TARGET}-shared SHARED IMPORTED)
 set_target_properties(${INSTALL_TARGET}-shared
     PROPERTIES
     IMPORTED_LOCATION \"\${PACKAGE_PREFIX_DIR}/${DESTINATION}/${COR_FILE_NAME}\"
 )
 "
-                        )
+                            )
 
-                        get_target_property(COR_IMPLIB_FILE_NAME ${INSTALL_TARGET}-shared COR_IMPLIB_FILE_NAME)
-                        if (NOT COR_IMPLIB_FILE_NAME MATCHES .*-NOTFOUND)
-                            file(APPEND
-                                ${CMAKE_BINARY_DIR}/corrosion/${EXTRA_TARGETS_EXPORT_NAME}
-                                "
+                            get_target_property(COR_IMPLIB_FILE_NAME ${INSTALL_TARGET}-shared COR_IMPLIB_FILE_NAME)
+                            if (NOT COR_IMPLIB_FILE_NAME MATCHES .*-NOTFOUND)
+                                file(APPEND "${EXPORT_FILE_PATH}"
+"
 set_target_properties(${INSTALL_TARGET}-shared
     PROPERTIES
     IMPORTED_IMPLIB \"\${PACKAGE_PREFIX_DIR}/${DESTINATION}/${COR_IMPLIB_FILE_NAME}\"
 )"
-                            )
-                        endif()
+                                )
+                            endif()
                     endif()
                 endif()
+            else()
+                message(FATAL_ERROR "Unknown target type ${TARGET_TYPE} for install target ${INSTALL_TARGET}")
             endif()
 
             # Executables can also have export tables, so they _might_ also need header files