if() funktion in CMakeLists.txt changes the compilation order of the components. (IDFGH-15343)

[Gemelon]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

IDF version.

v5.4.1

Operating System used.

Windows

How did you build your project?

VS Code IDE

If you are using Windows, please specify command line type.

None

What is the expected behavior?

I have a list with all reqiered components in my project. Whith config,I like to switch some components on or off.

set (requires "esp_event")
list(APPEND requires "base")
if(DEFINED CONFIG_BLINK_ENABLED)
   list(APPEND requires "blink")
endif()
set_property(GLOBAL PROPERTY requires_property ${requires})

What is the actual behavior?

Instead the ${requires} variable is empty wenn compiling the base componente. When I remove the IF statement the content of the ${requires} variabel is as expected.

Steps to reproduce.

1. this compiles fine

set (requires "esp_event")
list(APPEND requires "base")
list(APPEND requires "blink")
set_property(GLOBAL PROPERTY requires_property ${requires})

2. This compiles with error regardless of whether the variable is set or not

set (requires "esp_event")
list(APPEND requires "base")
if(DEFINED CONFIG_BLINK_ENABLED)
   list(APPEND requires "blink")
endif()
set_property(GLOBAL PROPERTY requires_property ${requires})

3. I have inserted two messages, one in this CMakeLists.txt at the main section:

set (requires "esp_event")
list(APPEND requires "base")
if(DEFINED CONFIG_BLINK_ENABLED)
   message("Blink is enabled")
   list(APPEND requires "blink")
endif()
set_property(GLOBAL PROPERTY requires_property ${requires})

and one in the CMakeLists.txt in the base component:

message("Requires: ${requires}")

What I found out is, without IF statement the output of the two messages is:

Blink is enabled
Requires: .....

with IF statement the output of the two messages is:

Requires:
Blink is enabled

It has changed the order of compilation and Requires is empty because blink is not compiled yet.

Build or installation Logs.

Diagnostic report archive.

No response

More Information.

No response

[igrr]

Hi @Gemelon, you are probably running into a limitation of the IDF build system that component dependencies (REQUIRES/PRIV_REQUIRES) can't themseleves depend on Kconfig options (see e.g. #11757 (comment))

In the current build system, you can only use conditions which depend on IDF build properties such as IDF_TARGET, when deciding which components to depend on. You can also use idf_component_optional_requires function to attach another component as a dependency after calling idf_component_register — however there is a limitation that that other component has to already be included into the build (either as a dependency of another component, or by specifying it explicitly by setting the COMPONENTS variable at project level).

We are planning to change this in IDF 6.0 — in the new build system it will be possible to use Kconfig options to decide which components to buid.

[Gemelon]

But "idf_component_optional_requires" is completely unknown, on the espressif site and in the whol internet. How should I use this funktion?
Which I don't understand either is, why do I need this very complicated system. In my understanding, when I declare "#include <esp_log.h>" then I made it clear that I needed this component.
The espressif system looks for my like:

• Ah you like this component to have?: yes
• You realy need this component?: yes
• You shure you need this component?:yes
• Think it over if you realy sure: yes I am sure
• That's your fault if you use this component, are you realy, realy,real sure?: YES the f... I AM SHURE.......

[igrr]

It's indeed not mentioned in the docs, but you can find many usages of it in esp-idf repository, for example:

esp-idf/components/esp_driver_cam/CMakeLists.txt

Lines 38 to 40 in 27d68f5

	if(CONFIG_PM_ENABLE)
	idf_component_optional_requires(PRIVATE esp_pm)
	endif()

and here is the description:

esp-idf/tools/cmake/component.cmake

Lines 602 to 613 in 27d68f5

	# idf_component_optional_requires
	#
	# @brief Add a dependency on a given component only if it is included in the build.
	#
	# Calling idf_component_optional_requires(PRIVATE dependency_name) has the similar effect to
	# target_link_libraries(${COMPONENT_LIB} PRIVATE idf::dependency_name), only if 'dependency_name'
	# component is part of the build. Otherwise, no dependency gets added. Multiple names may be given.
	#
	# @param[in] type of the dependency, one of: PRIVATE, PUBLIC, INTERFACE
	# @param[in, multivalue] list of component names which should be added as dependencies
	#
	function(idf_component_optional_requires req_type)

[Gemelon]

Yes, but I have to use this function inside the file it consumet it. That makes the whole idea absurd, becaus I want a list like all the example projects have with only one REQUIRES ${requires} in every component, so I don't need to copy all the entrys every time I create a new component. I have only to put REQUIRES ${requires} and all requiries are there. This works quite well so far, but some times I do need to switch off a componet like blink, when the board don't has a LED.

[igrr]

Okay, so what you want is to

• have several components in your project which add blink into PRIV_REQUIRES or REQUIRES
• add some code into the blink component's CMakeLists file so that the component gets "disabled" if CONFIG_BLINK_ENABLED is not set
• other components which depend on blink must not be modified in the process?

Have I understood your need correctly? (If not, could you please elaborate in a bit more detail?)

If the above is correct, what do you expect to happen when blink component is disabled? Will other components (which use blink) wrap calls to functions implemented inside blink component in #if CONFIG_BLINK_ENABLED? Or will blink component provide a dummy (empty) function for the boards which don't have an LED?