fix(cmakev2): include config-selected default components

tools/cmakev2/idf.cmake

@@ -582,6 +582,12 @@ endfunction()
         component is already included, the idf_component_include function
         simply returns, as there is nothing further to do except add a new
         alias target if requested.
+
+    PROJECT_DEFAULT_EXTRA_COMPONENTS
+        Internal list of additional components to include in the executable
+        created by idf_project_default. Components should use
+        idf_project_add_default_build_component rather than modifying this
+        property directly.
 #]]
 add_library(idf_build_properties INTERFACE)
 

tools/cmakev2/project.cmake

@@ -730,6 +730,28 @@ function(idf_build_generate_flasher_args)
                  INPUT "${build_dir}/flasher_args.json.in")
 endfunction()
 
+#[[api
+.. cmakev2:function:: idf_project_add_default_build_component
+
+    .. code-block:: cmake
+
+        idf_project_add_default_build_component(<component>...)
+
+    *component[in]*
+
+        Component name to include in the executable created by
+        :cmakev2:ref:`idf_project_default`.
+
+    Add components to the default project executable. This is intended for
+    components that need to be built based on sdkconfig alone, for example to
+    provide linker-section registrations, without making another component
+    depend on them. This is e.g. the case with coredump which is simply enabled
+    based on CONFIG_ESP_COREDUMP_ENABLE option, but no other components depend it.
+#]]
+function(idf_project_add_default_build_component)
+    idf_build_set_property(PROJECT_DEFAULT_EXTRA_COMPONENTS "${ARGN}" APPEND)
+endfunction()
+
 #[[
 .. cmakev2:macro:: __project_default
 
@@ -751,6 +773,11 @@ function(__project_default)
         set(root_components ${shim_components})
     else()
         set(root_components main)
+        idf_build_get_property(extra_default_components PROJECT_DEFAULT_EXTRA_COMPONENTS)
+        if(extra_default_components)
+            list(APPEND root_components ${extra_default_components})
+            list(REMOVE_DUPLICATES root_components)
+        endif()
     endif()
 
     idf_build_executable("${executable}"

tools/test_build_system/buildv2/test_default_components.py

@@ -0,0 +1,34 @@
+# SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: Apache-2.0
+import json
+import logging
+from pathlib import Path
+
+import pytest
+from test_build_system_helpers import IdfPyFunc
+
+
+@pytest.mark.usefixtures('test_app_copy')
+def test_config_selected_default_components(idf_py: IdfPyFunc) -> None:
+    """Components with a project_include.cmake that calls idf_project_add_default_build_component()
+    must be pulled into the default build when their Kconfig feature is enabled, even though nothing
+    in the project explicitly depends on them.
+
+    Enable coredump and gdbstub via sdkconfig.defaults, build, and assert both components end up in
+    build_components.
+    """
+    logging.info('Testing config-selected default components (coredump, gdbstub)')
+
+    # Coredump to UART (no dedicated coredump partition needed) and runtime gdbstub.
+    Path('sdkconfig.defaults').write_text('CONFIG_ESP_COREDUMP_ENABLE_TO_UART=y\nCONFIG_ESP_SYSTEM_GDBSTUB_RUNTIME=y\n')
+
+    idf_py('build')
+
+    proj_desc = json.loads(Path('build/project_description.json').read_text())
+    build_components = proj_desc.get('build_components', [])
+
+    for comp in ('espcoredump', 'esp_gdbstub'):
+        assert comp in build_components, (
+            f'{comp} should be added as a default build component when its feature is enabled, '
+            f'got build_components: {build_components}'
+        )