Library dependency finder ignores `build_src_flags`

[mcspr]

• Feature Request.
  Start by telling us what problem you’re trying to solve. Often a solution
  already exists! Don’t send pull requests to implement new features without first getting our
  support. Sometimes we leave features out on purpose to keep the project small.

---

Configuration

Operating system: Fedora 36

PlatformIO Version (platformio --version): PlatformIO Core, version 6.0.0a2

Description of problem

MCVE of the currently not working code is at https://github.com/mcspr/pio-scan-deps
Latest action run reproduces the error below https://github.com/mcspr/pio-scan-deps/runs/6246889310

The project is:

> tree
.
├── platformio.ini
├── src
│   ├── extra.cpp
│   ├── extra.h
│   └── main.cpp
└── vendor
    └── testlib
        ├── library.json
        └── src
            ├── testlib.cpp
            └── testlib.h

Where extra.cpp conditionally includes a local library

#if THIS_IS_A_TEST
#include <testlib.h>
... the rest of the module's code ...
#endif

When lib_ldf_mode = deep+ is set, PIO scanner will ignore the testlib.h
GCC still picks it up, though, resulting in a failed build

> env PLATFORMIO_BUILD_FLAGS="-DTHIS_IS_A_TEST=1" pio run -s
> env PLATFORMIO_SRC_BUILD_FLAGS="-DTHIS_IS_A_TEST=1" pio run -s
src/extra.cpp:4:10: fatal error: testlib.h: No such file or directory

*****************************************************************
* Looking for testlib.h dependency? Check our library registry!
*
* CLI  > platformio lib search "header:testlib.h"
* Web  > https://registry.platformio.org/search?q=header:testlib.h
*
*****************************************************************

    4 | #include <testlib.h>
      |          ^~~~~~~~~~~
compilation terminated.
*** [.pio/build/d1_mini/src/extra.cpp.o] Error 1

While I have noticed that examples in documentation only mention the build_flags = ... as a way to modify the dependency scanner behaviour...
I am not really sure whether this was intentional that project build flags are ignored?
Should the scanner do a 2nd pass with the project dependencies, while using the flags provided in the src_build_flags?

Steps to Reproduce

See the repo

If problems with PlatformIO Build System:

The content of platformio.ini:

[env]
platform = espressif8266
framework = arduino
build_flags = -g
lib_ldf_mode = deep+
lib_extra_dirs =
    vendor

[env:d1_mini]
board = d1_mini

Source file to reproduce issue:

// src/main.cpp

#include <Arduino.h>
#include "extra.h"

void setup() {
#if THIS_IS_A_TEST
    test();
#endif
}

void loop() {
}

// src/extra.cpp

#include <Arduino.h>

#if THIS_IS_A_TEST
#include <testlib.h>

void test() {
}
#endif

// src/extra.h

#pragma once

void test();

Plus, a dummy library consisting of lib/testlib/src/testlib.h and lib/testlib/src/testlib.cpp. Both are empty.

[ivankravets]

Where is THIS_IS_A_TEST defined? It seems this issue is a duplicate of #3113

The only solution to this issue is to switch to a native GCC Preprocessor. Currently, PlatformIO uses a virtual SCons/Pythonbased Preprocessor.

[mcspr]

Flag is set through the command line -DTHIS_IS_A_TEST=1 (or 0 to disable), and it does work correctly when global build_flags = ... is used.

As I understood the #3113 problem is with expressions and defines referencing other defines, which I have also happened to notice. SCons scanner still works out simple flags like this, though.

[ivankravets]

and it does work correctly when global build_flags = ... is used.

src_build_flags was renamed in Core 6.0 to the build_src_flags. It means flags will be applied ONLY to the files located in the main src folder of a project.

[mcspr]

Not yet renamed though, #4245, and grep does not find that name
Yes, the flag is only seen by the project file, but it hides a library include. Shouldn't it create a dependency on the lib?

[ivankravets]

Thanks, the option has been finally renamed.

#if THIS_IS_A_TEST

You have a typo here, please use #ifdef.

[mcspr]

...I have demonstrated that the option / flag works with build_flags = ... though! This is not a typo, it is intended to be used as a boolean.
The feature request / question was about the ability to influence LDF with project flags hiding library includes. Right now this just does not work.

[ivankravets]

Do you have in platformio.ini?

[env]
platform = espressif8266
framework = arduino
build_flags = 
  -g
  -DTHIS_IS_A_TEST=1

[mcspr]

See https://github.com/mcspr/pio-scan-deps, updated with what works and what does not as environments.