[nrf fromtree] cmake: support snippets scope for zephyr_get()

Fixes: #57139

Snippets provides the possibility of defining EXTRA_DTC_OVERLAY_FILE and
EXTRA_CONF_FILE in snippets.
Snippets must co-exist with existing infrastructure of
EXTRA_DTC_OVERLAY_FILE and EXTRA_CONF_FILE, and a user specifying a
snippet must be able to specify extra files for adjusting the snippet.

This means that if the following is specified:
`-DSNIPPET=some_snippet -DEXTRA_CONF_FILE=extra.conf`
then `extra.conf` may contain adjustments to the snippet.
Similar to sysbuild. Imagine a sysbuild controlled image uses a default
snippet for building, by ensuring that any extra
`-D<image>_EXTRA_CONF_FILE=extra.conf` arguments takes precedence over
the snippet we allow users to make adjustments if they need.

This commit introduces a snippets scope where snippet scoped variables
can be set with `zephyr_set()` and then `zephyr_get()` will take the
snippet scoped variables into consideration before returning.

Adjust calls to `zephyr_get(EXTRA_DTC_OVERLAY_FILE)` and
`zephyr_get(EXTRA_CONF_FILE)` to use `MERGE` to ensure all scopes are
considered.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
(cherry picked from commit ba48dd8)
(cherry picked from commit b9d092e)

cmake/modules/configuration_files.cmake

@@ -116,5 +116,5 @@ DTC_OVERLAY_FILE=\"dts1.overlay dts2.overlay\"")
 # The DTC_OVERLAY_FILE variable is now set to its final value.
 zephyr_boilerplate_watch(DTC_OVERLAY_FILE)
 
-zephyr_get(EXTRA_CONF_FILE SYSBUILD LOCAL VAR EXTRA_CONF_FILE OVERLAY_CONFIG)
-zephyr_get(EXTRA_DTC_OVERLAY_FILE SYSBUILD LOCAL)
+zephyr_get(EXTRA_CONF_FILE SYSBUILD LOCAL VAR EXTRA_CONF_FILE OVERLAY_CONFIG MERGE REVERSE)
+zephyr_get(EXTRA_DTC_OVERLAY_FILE SYSBUILD LOCAL MERGE REVERSE)

cmake/modules/extensions.cmake

@@ -2568,9 +2568,13 @@ function(zephyr_get variable)
  else()
  set(sysbuild_${var})
  endif()
+
+ if(TARGET snippets_scope)
+ get_property(snippets_${var} TARGET snippets_scope PROPERTY ${var})
+ endif()
  endforeach()
 
- set(scopes "sysbuild;CACHE;ENV;current")
+ set(scopes "sysbuild;CACHE;snippets;ENV;current")
  if(GET_VAR_REVERSE)
  list(REVERSE scopes)
  endif()

cmake/modules/snippets.cmake

@@ -93,10 +93,6 @@ function(zephyr_process_snippets)
  endif()
  include(${snippets_generated})
 
- # Propagate include()d build system settings to the caller.
- set(DTC_OVERLAY_FILE ${DTC_OVERLAY_FILE} PARENT_SCOPE)
- set(OVERLAY_CONFIG ${OVERLAY_CONFIG} PARENT_SCOPE)
-
  # Create the 'snippets' target. Each snippet is printed in a
  # separate command because build system files are not fond of
  # newlines.

scripts/snippets.py

@@ -133,6 +133,9 @@ def print_cmake(self):
 # The paths to all the snippet.yml files. One snippet
 # can have multiple snippet.yml files.
 set(SNIPPET_PATHS {snippet_path_list})
+
+# Create variable scope for snippets build variables
+zephyr_create_scope(snippets)
 ''')
 
  for snippet_name in snippet_names:
@@ -168,7 +171,7 @@ def print_appends(self, appends: Appends, indent: int):
  space = ' ' * indent
  for name, values in appends.items():
  for value in values:
- self.print(f'{space}list(APPEND {name} {value})')
+ self.print(f'{space}zephyr_set({name} {value} SCOPE snippets APPEND)')
 
  def print(self, *args, **kwargs):
  kwargs['file'] = self.out_file