[libcamera-devel] [PATCH v2] clang-format: Regroup sort orders

[Kieran Bingham]

Utilise the clang-format header sort to provide a regex based pattern
match for our header inclusion coding style.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
A sample of all headers from the project (+ a couple of extra tests)
parsed through this can be seen at 
   https://paste.ubuntu.com/p/Bt87C6M77y/

This was generated by:
 git grep -h "^#include" | sort | uniq  > all-headers.cpp
 git add all-headers.cpp
 git commit all-headers.cpp -m "Header Test"
 ./utils/checkstyle.py | patch -p0

While some false positives are visible in this list
 (for instance <camera_metadata_hidden.h> in c/system headers section)
this provides a great deal of the checks automatically, and the
remaining cases may have to be spotted during review.

 .clang-format                  | 49 +++++++++++++++++++++++++++++++---
 Documentation/coding-style.rst | 20 +++++++++++---
 2 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/.clang-format b/.clang-format
index 3a8a896e373d..56cfbfa1bec4 100644
--- a/.clang-format
+++ b/.clang-format
@@ -66,10 +66,53 @@ ExperimentalAutoDetectBinPacking: false
 FixNamespaceComments: true
 ForEachMacros:
   - 'udev_list_entry_foreach'
-IncludeBlocks: Preserve
+SortIncludes: true
+IncludeBlocks: Regroup
 IncludeCategories:
-  - Regex: '.*'
-    Priority: 1
+  # Headers matching the name of the component are matched automatically.
+  # Priority 1
+  # Headers in <> with an extension. (+system libraries)
+  - Regex:           '<([A-Za-z0-9\-_])+\.h>'
+    Priority:        2 
+  - Regex:           '<sys/.*>'
+    Priority:        2
+  # Qt includes (match before C++ standard library)
+  - Regex:           '<Q([A-Za-z0-9\-_])+>'
+    Priority:        10
+    CaseSensitive:   true
+  # C++ standard library includes (no extension)
+  - Regex:           '<([A-Za-z0-9\-_/])+>'
+    Priority:        3
+  # Linux headers, as a second group/subset of system headers
+  - Regex:           '<linux/.*>'
+    Priority:        4
+  # Headers for libcamera Base support
+  - Regex:           '<libcamera/base/private.h>'
+    Priority:        5
+  - Regex:           '<libcamera/base/.*\.h>'
+    Priority:        6
+  # Public API Headers for libcamera, which are not in a subdir (i.e. ipa/,internal/)
+  - Regex:           '<libcamera/([A-Za-z0-9\-_])+.h>'
+    Priority:        7
+  # IPA Interfaces
+  - Regex:           '<libcamera/ipa/.*\.h>'
+    Priority:        8
+  # libcamera Internal headers in ""  
+  - Regex:           '"libcamera/internal/.*\.h"'
+    Priority:        9
+  # Other libraries headers with one group per library (.h or .hpp)
+  - Regex:           '<.*/.*\.hp*>'
+    Priority:        10
+  # local modular includes "path/file.h" (.h or .hpp)
+  - Regex:           '"(.*/)+.*\.hp*"'
+    Priority:        11
+  # Other local headers "file.h" with extension (.h or .hpp)
+  - Regex:           '".*.hp*"'
+    Priority:        12
+  # Any unmatched line, separated from the last group
+  - Regex:	     '"*"'
+    Priority:        100
+
 IncludeIsMainRegex: '(_test)?$'
 IndentCaseLabels: false
 IndentPPDirectives: None
diff --git a/Documentation/coding-style.rst b/Documentation/coding-style.rst
index 30c1778ed8bf..e4f1bb26024e 100644
--- a/Documentation/coding-style.rst
+++ b/Documentation/coding-style.rst
@@ -70,19 +70,31 @@ macro. For .cpp files, if the file implements an API declared in a header file,
 that header file shall be included first in order to ensure it is
 self-contained.
 
+While the following list is extensive, it documents the expected behaviour
+defined by the clang-format configuraiton and tooling should assist with
+ordering.
+
 The headers shall be grouped and ordered as follows:
 
 1. The header declaring the API being implemented (if any)
-2. The C and C++ system and standard library headers
-3. Other libraries' headers, with one group per library
-4. Other project's headers
+2. The C standard library and system headers
+3. The C++ standard library headers
+4. Linux kernel headers
+5. The libcamera base private header if required
+6. The libcamera base library headers
+7. The libcamera public API headers
+8. The libcamera IPA interfaces
+9. The internal libcamera headers
+10. Other libraries' headers, with one group per library
+11. Local headers grouped by subdirectory
+12. Any local headers
 
 Groups of headers shall be separated by a single blank line. Headers within
 each group shall be sorted alphabetically.
 
 System and library headers shall be included with angle brackets. Project
 headers shall be included with angle brackets for the libcamera public API
-headers, and with double quotes for other libcamera headers.
+headers, and with double quotes for internal libcamera headers.
 
 
 C++ Specific Rules
-- 
2.30.2