runners: remove dependencies from runners

Today, there is a build target is added for each runner: flash, debug,
debugserver, attach.

And those runners will have a dependency to Zephyr logical target that
is built before invoking `west <runner>`.

This design has some flaws, mainly that additional dependencies directly
on the target will not be built when running `west <runner>` directly.
That generator expressions cannot be used for the DEPENDS argument.

Instead, the build target `<runner>` will not have any dependencies, and
will raise a build error if a dependency is added to the target.
Due to how `add_dependencies()` work, this must be done as a build time
check, and not configure time check.

`west <runner>` will invoke a build before executing the runner, and
this way ensure the build target is up-to-date, which again removes the
need for a dedicated `west_<runner>_target`.

It also minimizes the risk of developer errors, as developers no longer
need to consider the need for adding additional dependencies.
If a custom target is part of the default `all` build, then it's ensured
to be up-to-date.

Fixes: Issue reported on slack.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

cmake/app/boilerplate.cmake

@@ -654,8 +654,6 @@ endif()
 #
 # Currently used properties:
 # - COMPILES_OPTIONS: Used by application memory partition feature
-# - ${TARGET}_DEPENDENCIES: additional dependencies for targets that need them
-#   like flash (FLASH_DEPENDENCIES), debug (DEBUG_DEPENDENCIES), etc.
 add_custom_target(zephyr_property_target)
 
 # "app" is a CMake library containing all the application code and is

cmake/flash/CMakeLists.txt

@@ -159,37 +159,26 @@ foreach(target flash debug debugserver attach)
     set(RUNNER_VERBOSE)
   endif()
 
-  # We pass --skip-rebuild here because the DEPENDS value ensures the
-  # build is already up to date before west is run.
   if(WEST)
-    set(cmd
-      ${CMAKE_COMMAND} -E env
-      ${WEST}
-      ${RUNNER_VERBOSE}
-      ${target}
-      --skip-rebuild
-      DEPENDS ${RUNNERS_DEPS}
-              $<TARGET_PROPERTY:zephyr_property_target,${TARGET_UPPER}_DEPENDENCIES>
-      WORKING_DIRECTORY ${APPLICATION_BINARY_DIR}
-      )
-
     add_custom_target(${target}
+      # This script will print an error message and fail if <target> has added
+      # dependencies. This is done using dedicated CMake script, as
+      # `cmake -E {true|false}` is not available until CMake 3.16.
+      COMMAND ${CMAKE_COMMAND}
+        -DTARGET=${target}
+        -DDEPENDENCIES="$<TARGET_PROPERTY:${target},MANUALLY_ADDED_DEPENDENCIES>"
+        -P ${CMAKE_CURRENT_LIST_DIR}/check_runner_dependencies.cmake
       COMMAND
-      ${cmd}
+        ${CMAKE_COMMAND} -E env
+        ${WEST}
+        ${RUNNER_VERBOSE}
+        ${target}
+      WORKING_DIRECTORY
+        ${APPLICATION_BINARY_DIR}
       COMMENT
-      ${comment}
+        ${comment}
       USES_TERMINAL
-      )
+    )
-
-    # This is an artificial target to allow west to ensure all dependencies of
-    # target is build before carrying out the actual command.
-    # This allows `west` to run just the dependencies before flashing.
-    add_custom_target(west_${target}_depends
-      COMMAND ${CMAKE_COMMAND} -E echo ""
-      DEPENDS ${RUNNERS_DEPS}
-              $<TARGET_PROPERTY:zephyr_property_target,${TARGET_UPPER}_DEPENDENCIES>
-      USES_TERMINAL
-      )
   else()
     add_custom_target(${target}
       COMMAND ${CMAKE_COMMAND} -E echo \"West was not found in path. To support

cmake/flash/check_runner_dependencies.cmake

@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: Apache-2.0
+
+# The purpose of this script is to ensure that no runners targets contains
+# additional dependencies.
+#
+# If the target contains dependencies, an error will be printed.
+#
+# Arguments to the script
+#
+# TARGET:       The target being checked.
+# DEPENDENCIES: List containing dependencies on target.
+
+if(DEPENDENCIES)
+  string(REPLACE ";" " " DEPENDENCIES "${DEPENDENCIES}")
+  message(FATAL_ERROR
+          "`${TARGET}` cannot have dependencies, please remove "
+          "`add_dependencies(${TARGET} ${DEPENDENCIES})` in build system."
+  )
+endif()

scripts/west_commands/run_common.py

@@ -272,9 +272,8 @@ def load_cmake_cache(build_dir, args):
 
 def rebuild(command, build_dir, args):
     _banner(f'west {command.name}: rebuilding')
-    extra_args = ['--target', 'west_' + command.name + '_depends']
     try:
-        zcmake.run_build(build_dir, extra_args=extra_args)
+        zcmake.run_build(build_dir)
     except CalledProcessError:
         if args.build_dir:
             log.die(f're-build in {args.build_dir} failed')