IWYU should not suggest adding two copies of the same header

[ptomato]

It can happen, when using e.g. a precompiled header, that IWYU suggests adding the same header in both quotes and angle brackets. This seems undesirable.

Minimal reproducer:

a.cpp:

#include "a.h"
void foo() {}

a.h:

#pragma once
void foo();

b.h: (the "precompiled" header)

#include <a.h>

Output:

$ include-what-you-use -I. -include b.h a.cpp

(a.h has correct #includes/fwd-decls)

a.cpp should add these lines:
#include <a.h>

a.cpp should remove these lines:

The full include-list for a.cpp:
#include <a.h>
#include "a.h"  // for foo
---

I'm guessing it's because b.h includes the header in angle brackets already, so IWYU decides it's a system header, but somehow even though it does realize "a.h" is already included (it says, for foo) it doesn't realize that <a.h> needn't be included to provide foo.

[kimgr]

The angle/quote curse strikes again. I wonder if you can work around this using the --prefix_header_includes switch?

[ptomato]

Thanks for the suggestion. --prefix_header_includes=keep seems to fix it for some of my files, but not all.

[bolshakov-a]

I have a dirty fix on my draft branch and a commit to use quoted form of current directory header paths rather than bracketed one, but the latter breaks a lot of tests beacause #include "tests/cxx/header.h" lines are replaced by #include "header.h".

[ACSimon33]

I have a similar problem but not for precompiled headers. IWYU suggests including gtest/gtest.h as well as <gtest/gtest.h> to me:

#include "gtest/gtest.h"                   // for AssertionResult, Message
#include <gtest/gtest.h>                   // for Test, TestInfo (ptr only)

Does anyone have an idea what's happening here? --prefix_header_includes doesn't help here.

Edit 1:
IWYU 0.18.0
Clang 14.0.3
GTest 1.12.1

Edit 2:
GTest uses IWYU pragmas now since version 1.12.0:

// IWYU pragma: private, include "gtest/gtest.h"
// IWYU pragma: friend gtest/.*
// IWYU pragma: friend gmock/.*

Edit 3:
It works as expected when I use a mapping file instead of relying on the pragmas. I guess there is either something wrong with how GTest uses the pragmas or a bug in IWYU.

[kimgr]

@ACSimon33 I can't say for sure, but I'm guessing you have includes using <gtest/gtest.h> in your code? The pragmas in gtest all seem to produce "gtest/gtest.h" quoting.

[ceggers-arri]

Similar/same problem for me (new user):
I already include <gtest/gtest.h>, but iwyu asks to also include "gtest/gtest.h". The full include-list then contains both variants.

As gtest/gtest.h is part of my toolchain / Linux distro, for me it is a "system header" and I would like to stay with angle brackets.