Add header ignore option to readability-duplicate-include

[nick-potenski]

Our codebase has a few cases where duplicate includes are expected. For example, we have a pair of headers to manage enabling and disabling structure packing which are typically included around a structure that we want packed on a byte boundary.

#include "pack_begin.h"
typedef struct {
} a_packed_struct;
#include "pack_end.h"

typedef struct {
} an_unpacked_struct;

#include "pack_begin.h"  //  readability-duplicate-include warns here
typedef struct {
} another_packed_struct;
#include "pack_end.h" //  readability-duplicate-include warns here

It would be nice if this checker provided a configuration option taking a list of strings or regexes defining headers that are OK to duplicate.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Nick Potenski (nick-potenski)

Our codebase has a few cases where duplicate includes are expected. For example, we have a pair of headers to manage enabling and disabling structure packing which are typically included around a structure that we want packed on a byte boundary.

#include "pack_begin.h"
typedef struct {
} a_packed_struct;
#include "pack_end.h"

typedef struct {
} an_unpacked_struct;

#include "pack_begin.h"  //  readability-duplicate-include warns here
typedef struct {
} another_packed_struct;
#include "pack_end.h" //  readability-duplicate-include warns here

It would be nice if this checker provided a configuration option taking a list of strings or regexes defining headers that are OK to duplicate.

[firewave]

Maybe it could check for an include guard and do not warn about includes which have none (as opt-in option).

[LegalizeAdulthood]

Use // NOLINT(readability-duplicate-include) as shown here: https://godbolt.org/z/GYv3a6vqT

[nick-potenski]

I was really hoping for a better solution than NOLINT considering how many instances of this exist in our codebase. NOLINT seems like it should be used for the exception, not an established pattern.

[nick-potenski]

As a point of comparision, misc-header-include-cycle provides an option to do a similar thing and as a more usable alternative to NOLINT.

IgnoredFilesList

Provides a way to exclude specific files/headers from the warnings raised by a check. This can be achieved by specifying a semicolon-separated list of regular expressions or filenames. This option can be used as an alternative to //NOLINT when using it is not possible. The default value of this option is an empty string, indicating that no files are ignored by default.

[vbvictor]

I believe this is a reasonable request and IMO not that hard to achieve given we already have similar option.