feat(cmakev2/idf): add git submodules initialization

Initialize submodules that are not yet initialized, and issue a warning
for submodules that do not match the recorded hash in the git tree.

Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>

tools/cmakev2/idf.cmake

@@ -348,6 +348,89 @@ function(__init_components)
     endforeach()
 endfunction()
 
+#[[
+   __init_submodules()
+
+   Initialize submodules that are not yet initialized, and issue a warning for
+   submodules that do not match the recorded hash in the git tree.
+#]]
+function(__init_submodules)
+    idf_build_get_property(idf_path IDF_PATH)
+    idf_build_get_property(git GIT)
+
+    # For internal use: Skip the submodule check if running on GitLab CI
+    # and the job is configured to not clone submodules.
+    if("$ENV{IDF_SKIP_CHECK_SUBMODULES}" STREQUAL "1")
+        idf_msg("skip submodule check on internal CI")
+        return()
+    endif()
+
+    if(NOT git)
+        idf_warn("Git executable was not found. Git submodule checks will not be executed. "
+                 "If you have any build issues at all, start by adding git executable to "
+                 "the PATH and rerun cmake to not see this warning again.")
+        return()
+    endif()
+
+    execute_process(
+        COMMAND ${git} submodule status
+        WORKING_DIRECTORY ${idf_path}
+        OUTPUT_VARIABLE status
+        ERROR_VARIABLE stderr
+        RESULT_VARIABLE rv
+    )
+
+    if(rv)
+        idf_warn("Git submodule status command failed(${rv}): ${stderr}"
+                 "Git submodule checks will not be performed. ")
+        return()
+    endif()
+
+    __split(STRING "${status}"
+            OUTPUT lines
+            REMOVE_EMPTY)
+
+    # The output of the git submodule status command is not guaranteed to be
+    # stable. It may be necessary to check the GIT_VERSION_STRING and make
+    # adjustments in the future.
+    foreach(line IN LISTS lines)
+        string(REGEX MATCH "(.)[0-9a-f]+ ([^\( ]+) ?" _ignored "${line}")
+        set(status "${CMAKE_MATCH_1}")
+        set(submodule_path "${CMAKE_MATCH_2}")
+
+        if("${status}" STREQUAL "-")  # missing submodule
+            idf_msg("Initialising new submodule ${submodule_path}...")
+            execute_process(
+                COMMAND ${git} submodule update --init --recursive ${submodule_path}
+                WORKING_DIRECTORY ${idf_path}
+                ERROR_VARIABLE stderr
+                RESULT_VARIABLE rv
+                )
+            if(rv)
+                idf_die("Git submodule '${submodule_path}' init failed(${rv}): ${stderr}")
+            endif()
+
+        elseif(NOT "${status}" STREQUAL " ")
+            idf_warn("Git submodule ${submodule_path} is out of date. "
+                     "Run the following command to fix: "
+                     "git submodule update --init --recursive")
+        endif()
+
+        # Ensure CMake is rerun if the submodule's .git file is modified or
+        # altered, such as in the case of an accidental deinitialization.
+        get_filename_component(submodule_abs_path ${submodule_path} ABSOLUTE BASE_DIR ${idf_path})
+        set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${submodule_abs_path}/.git)
+        # If the HEAD file in the submodule's directory changes (i.e., if there
+        # are commit changes), it will at least display the 'out of date'
+        # warning.
+        set(submodule_head "${idf_path}/.git/modules/${submodule_path}/HEAD")
+        if(EXISTS "${submodule_head}")
+            set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${submodule_head})
+        endif()
+
+    endforeach()
+endfunction()
+
 #[[
    The idf_build_properties interface target is exclusively used to store
    information about global build properties and is not linked or used in any
@@ -387,6 +470,9 @@ __init_idf_path()
 # Determine git executable and set GIT build property.
 __init_git()
 
+# Initialize git submodules.
+__init_submodules()
+
 # Initialize the IDF_VER build property.
 __init_idf_version()