Cmake+Rust: Disable test precompile feature

Precompiling the test executable causes `sudo make install` to fail.
The issue is that because we don't know the OUTPUT file path for the
test executable, CMake can't know if it doesn't need to rerun that
command, so it will run it with any call to `make`. The problem is that
cargo is will fail to run with `sudo` on many systems.

This is generally okay, because we just fixed the issue where we had
been compiling the dependencies for each module. Now that we only build
the dependencies once, building the test executable is actually very
fast. So compiling it during the test isn't so bad.

Author: val-ms

cmake/FindRust.cmake

@@ -87,15 +87,23 @@
 #   set_property(TEST yourlib PROPERTY ENVIRONMENT ${ENVIRONMENT})
 #   ```
 #
+# Experimental: Precompile the Tests Executable
+# ~~~~~~~~~~~~
+# This feature will cause install failures if you `sudo make install` because
+# it will recompile the test executable with sudo and Cargo is likely to fail to
+# run with sudo.
+# This cannot be fixed unless we can predetermine the test exeecutable OUTPUT
+# filepath. See: https://github.com/rust-lang/cargo/issues/1924
+#
 # If your library has unit tests AND your library DOES depend on your C
 # libraries, you can precompile the unit tests application with some extra
 # parameters to `add_rust_test()`:
 # - `PRECOMPILE_TESTS TRUE`
-# - `DEPENDS <the CMake target name for your C library dependency>`
-# - `ENVIRONMENT <a linked list of environment vars to build the Rust lib>`
+# - `PRECOMPILE_DEPENDS <the CMake target name for your C library dependency>`
+# - `PRECOMPILE_ENVIRONMENT <a linked list of environment vars to build the Rust lib>`
 #
-# The `DEPENDS` option is required so CMake will build the C library first.
-# The `ENVIRONMENT` option is required for use in your `build.rs` file so you
+# The `PRECOMPILE_DEPENDS` option is required so CMake will build the C library first.
+# The `PRECOMPILE_ENVIRONMENT` option is required for use in your `build.rs` file so you
 # can tell rustc how to link to your C library.
 #
 # For example:
@@ -105,8 +113,8 @@
 #       SOURCE_DIRECTORY "${CMAKE_SOURCE_DIR}/yourlib"
 #       BINARY_DIRECTORY "${CMAKE_BINARY_DIR}"
 #       PRECOMPILE_TESTS TRUE
-#       DEPENDS ClamAV::libclamav
-#       ENVIRONMENT "${ENVIRONMENT}"
+#       PRECOMPILE_DEPENDS ClamAV::libclamav
+#       PRECOMPILE_ENVIRONMENT "${ENVIRONMENT}"
 #   )
 #   set_property(TEST yourlib PROPERTY ENVIRONMENT ${ENVIRONMENT})
 #   ```
@@ -321,8 +329,8 @@ endfunction()
 
 function(add_rust_test)
     set(options)
-    set(oneValueArgs NAME SOURCE_DIRECTORY BINARY_DIRECTORY PRECOMPILE_TESTS DEPENDS)
-    set(multiValueArgs ENVIRONMENT)
+    set(oneValueArgs NAME SOURCE_DIRECTORY BINARY_DIRECTORY PRECOMPILE_TESTS PRECOMPILE_DEPENDS)
+    set(multiValueArgs PRECOMPILE_ENVIRONMENT)
     cmake_parse_arguments(ARGS "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
 
     set(MY_CARGO_ARGS "test")
@@ -339,10 +347,10 @@ function(add_rust_test)
     list(JOIN MY_CARGO_ARGS " " MY_CARGO_ARGS_STRING)
 
     if(ARGS_PRECOMPILE_TESTS)
-        list(APPEND ARGS_ENVIRONMENT "CARGO_CMD=test" "CARGO_TARGET_DIR=${ARGS_BINARY_DIRECTORY}")
+        list(APPEND ARGS_PRECOMPILE_ENVIRONMENT "CARGO_CMD=test" "CARGO_TARGET_DIR=${ARGS_BINARY_DIRECTORY}")
         add_custom_target(${ARGS_NAME}_tests ALL
-            COMMAND ${CMAKE_COMMAND} -E env ${ARGS_ENVIRONMENT} ${cargo_EXECUTABLE} ${MY_CARGO_ARGS} --color always --no-run
-            DEPENDS ${ARGS_DEPENDS}
+            COMMAND ${CMAKE_COMMAND} -E env ${ARGS_PRECOMPILE_ENVIRONMENT} ${cargo_EXECUTABLE} ${MY_CARGO_ARGS} --color always --no-run
+            DEPENDS ${ARGS_PRECOMPILE_DEPENDS}
             WORKING_DIRECTORY ${ARGS_SOURCE_DIRECTORY}
         )
     endif()

unit_tests/CMakeLists.txt

@@ -349,9 +349,7 @@ endif()
 add_rust_test(NAME libclamav_rust
     SOURCE_DIRECTORY "${CMAKE_SOURCE_DIR}/libclamav_rust"
     BINARY_DIRECTORY "${CMAKE_BINARY_DIR}"
-    PRECOMPILE_TESTS TRUE
-    DEPENDS ClamAV::libclamav
-    ENVIRONMENT "${ENVIRONMENT}"
+    PRECOMPILE_TESTS FALSE # Cannot precompile, because `sudo make install` will fail. See notes in FindRust.cmake.
 )
 set_property(TEST libclamav_rust PROPERTY ENVIRONMENT ${ENVIRONMENT})