ci: Check that `#include "*.h"` works as a single include

Lesser form of include-what-you-use: at least guarantees that header
file did not forget to include something through some other included
file.

Activate run_single_includes_tests on CI.
Fix some IWYU violations.

References #5321

13 files changed, 153 insertions, 33 deletions

diff --git a/.ci/common/test.sh b/.ci/common/test.sh
index b28e46a4df..4137472385 100644
--- a/.ci/common/test.sh
+++ b/.ci/common/test.sh
@@ -109,6 +109,10 @@ run_oldtests() {
   check_core_dumps
 }
 
+run_single_includes_tests() {
+  ${MAKE_CMD} -C "${BUILD_DIR}" check-single-includes
+}
+
 install_nvim() {
   ${MAKE_CMD} -C "${BUILD_DIR}" install
 
diff --git a/.ci/run_tests.sh b/.ci/run_tests.sh
index 6347ac15d4..d994db471f 100755
--- a/.ci/run_tests.sh
+++ b/.ci/run_tests.sh
@@ -10,6 +10,7 @@ source "${CI_DIR}/common/test.sh"
 check_core_dumps --delete quiet
 
 prepare_build
+run_single_includes_tests
 build_nvim
 
 if [ "$CLANG_SANITIZER" != "TSAN" ]; then
diff --git a/Makefile b/Makefile
index fed84582a9..47fb1e5edd 100644
--- a/Makefile
+++ b/Makefile
@@ -134,4 +134,7 @@ clint:
 
 lint: clint testlint
 
+check-single-includes: build/.ran-cmake
+	+$(BUILD_CMD) -C build check-single-includes
+
 .PHONY: test testlint functionaltest unittest lint clint clean distclean nvim libnvim cmake deps install
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 22cf1f3a3d..8af2dcf5f6 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -48,6 +48,7 @@ file(MAKE_DIRECTORY ${GENERATED_DIR})
 file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR})
 
 file(GLOB NEOVIM_SOURCES *.c)
+file(GLOB NEOVIM_HEADERS *.h)
 
 foreach(subdir
         os
@@ -65,10 +66,11 @@ foreach(subdir
   file(MAKE_DIRECTORY ${GENERATED_DIR}/${subdir})
   file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/${subdir})
   file(GLOB sources ${subdir}/*.c)
+  file(GLOB headers ${subdir}/*.h)
   list(APPEND NEOVIM_SOURCES ${sources})
+  list(APPEND NEOVIM_HEADERS ${headers})
 endforeach()
 
-file(GLOB_RECURSE NEOVIM_HEADERS *.h)
 file(GLOB UNIT_TEST_FIXTURES ${PROJECT_SOURCE_DIR}/test/unit/fixtures/*.c)
 
 # Sort file lists to ensure generated files are created in the same order from
@@ -152,6 +154,19 @@ separate_arguments(C_FLAGS_ARRAY UNIX_COMMAND ${CMAKE_C_FLAGS})
 separate_arguments(C_FLAGS_${build_type}_ARRAY UNIX_COMMAND ${CMAKE_C_FLAGS_${build_type}})
 set(gen_cflags ${gen_cflags} ${C_FLAGS_${build_type}_ARRAY} ${C_FLAGS_ARRAY})
 
+function(get_preproc_output varname iname)
+  if(MSVC)
+    set(${varname} /P /Fi${iname} PARENT_SCOPE)
+  else()
+    set(${varname} -E -o ${iname} PARENT_SCOPE)
+  endif()
+endfunction()
+
+# NEOVIM_GENERATED_FOR_HEADERS: header files generated to be included in headers
+# NEOVIM_GENERATED_FOR_SOURCES: header files generated to be included in sources
+# NEOVIM_GENERATED_SOURCES: generated source files
+# These lists should be mutually exclusive
+
 foreach(sfile ${NEOVIM_SOURCES}
               "${PROJECT_SOURCE_DIR}/src/nvim/regexp_nfa.c"
               ${GENERATED_API_DISPATCH})
@@ -166,26 +181,22 @@ foreach(sfile ${NEOVIM_SOURCES}
     set(f "${d}/${f}")
     set(r "${d}/${r}")
   endif()
-  set(gf1 "${GENERATED_DIR}/${r}.c.generated.h")
-  set(gf2 "${GENERATED_INCLUDES_DIR}/${r}.h.generated.h")
-  set(gf3 "${GENERATED_DIR}/${r}.i")
+  set(gf_c_h "${GENERATED_DIR}/${r}.c.generated.h")
+  set(gf_h_h "${GENERATED_INCLUDES_DIR}/${r}.h.generated.h")
+  set(gf_i "${GENERATED_DIR}/${r}.i")
 
-  if(MSVC)
-    set(PREPROC_OUTPUT /P /Fi${gf3})
-  else()
-    set(PREPROC_OUTPUT -E -o ${gf3})
-  endif()
+  get_preproc_output(PREPROC_OUTPUT ${gf_i})
 
   add_custom_command(
-    OUTPUT "${gf1}" "${gf2}"
+    OUTPUT "${gf_c_h}" "${gf_h_h}"
     COMMAND ${CMAKE_C_COMPILER} ${sfile} ${PREPROC_OUTPUT} ${gen_cflags} ${C_FLAGS_ARRAY}
-    COMMAND "${LUA_PRG}" "${HEADER_GENERATOR}" "${sfile}" "${gf1}" "${gf2}" "${gf3}"
+    COMMAND "${LUA_PRG}" "${HEADER_GENERATOR}" "${sfile}" "${gf_c_h}" "${gf_h_h}" "${gf_i}"
     DEPENDS "${HEADER_GENERATOR}" "${sfile}"
     )
-  list(APPEND NEOVIM_GENERATED_SOURCES "${gf1}")
-  list(APPEND NEOVIM_GENERATED_SOURCES "${gf2}")
+  list(APPEND NEOVIM_GENERATED_FOR_SOURCES "${gf_c_h}")
+  list(APPEND NEOVIM_GENERATED_FOR_HEADERS "${gf_h_h}")
   if(${d} MATCHES "^api$" AND NOT ${f} MATCHES "^api/helpers.c$")
-    list(APPEND API_HEADERS ${gf2})
+    list(APPEND API_HEADERS ${gf_h_h})
   endif()
 endforeach()
 
@@ -210,17 +221,23 @@ add_custom_command(OUTPUT ${GENERATED_API_DISPATCH} ${GENERATED_FUNCS_METADATA}
     ${CMAKE_CURRENT_LIST_DIR}/api/dispatch_deprecated.lua
 )
 
-list(APPEND NEOVIM_GENERATED_SOURCES
-  "${PROJECT_BINARY_DIR}/config/auto/pathdef.c"
-  "${GENERATED_API_DISPATCH}"
+list(APPEND NEOVIM_GENERATED_FOR_HEADERS
   "${GENERATED_EX_CMDS_ENUM}"
-  "${GENERATED_EX_CMDS_DEFS}"
   "${GENERATED_EVENTS_ENUM}"
+)
+
+list(APPEND NEOVIM_GENERATED_FOR_SOURCES
+  "${GENERATED_API_DISPATCH}"
+  "${GENERATED_EX_CMDS_DEFS}"
   "${GENERATED_EVENTS_NAMES_MAP}"
   "${GENERATED_OPTIONS}"
   "${GENERATED_UNICODE_TABLES}"
 )
 
+list(APPEND NEOVIM_GENERATED_SOURCES
+  "${PROJECT_BINARY_DIR}/config/auto/pathdef.c"
+)
+
 add_custom_command(OUTPUT ${GENERATED_EX_CMDS_ENUM} ${GENERATED_EX_CMDS_DEFS}
   COMMAND ${LUA_PRG} ${EX_CMDS_GENERATOR}
       ${PROJECT_SOURCE_DIR}/src/nvim ${GENERATED_INCLUDES_DIR} ${GENERATED_DIR}
@@ -237,7 +254,7 @@ add_custom_command(OUTPUT ${GENERATED_FUNCS} ${FUNCS_DATA}
     ${GENERATED_FUNCS_HASH_INPUT} --output-file=${GENERATED_FUNCS}
     DEPENDS ${FUNCS_GENERATOR} ${EVAL_DEFS_FILE} ${API_METADATA}
 )
-list(APPEND NEOVIM_GENERATED_SOURCES
+list(APPEND NEOVIM_GENERATED_FOR_SOURCES
   "${GENERATED_FUNCS}")
 
 add_custom_command(OUTPUT ${GENERATED_EVENTS_ENUM} ${GENERATED_EVENTS_NAMES_MAP}
@@ -252,6 +269,15 @@ add_custom_command(OUTPUT ${GENERATED_OPTIONS}
   DEPENDS ${OPTIONS_GENERATOR} ${OPTIONS_LIST_FILE}
 )
 
+# Check that NEOVIM_GENERATED_FOR_SOURCES and NEOVIM_GENERATED_FOR_HEADERS are mutually exclusive
+
+foreach(hfile ${NEOVIM_GENERATED_FOR_HEADERS})
+  list(FIND NEOVIM_GENERATED_FOR_SOURCES ${hfile} hfile_idx)
+  if(NOT ${hfile_idx} EQUAL -1)
+    message(FATAL_ERROR "File included in both NEOVIM_GENERATED_FOR_HEADERS and NEOVIM_GENERATED_FOR_SOURCES")
+  endif()
+endforeach()
+
 # Our dependencies come first.
 
 if (LibIntl_FOUND)
@@ -286,8 +312,8 @@ if(JEMALLOC_FOUND)
   list(APPEND NVIM_EXEC_LINK_LIBRARIES ${JEMALLOC_LIBRARIES})
 endif()
 
-add_executable(nvim ${NEOVIM_GENERATED_SOURCES} ${NEOVIM_SOURCES}
-  ${NEOVIM_HEADERS})
+add_executable(nvim ${NEOVIM_GENERATED_FOR_SOURCES} ${NEOVIM_GENERATED_FOR_HEADERS}
+  ${NEOVIM_GENERATED_SOURCES} ${NEOVIM_SOURCES} ${NEOVIM_HEADERS})
 target_link_libraries(nvim ${NVIM_EXEC_LINK_LIBRARIES})
 install_helper(TARGETS nvim)
 
@@ -361,17 +387,97 @@ elseif(CLANG_TSAN)
   set_property(TARGET nvim APPEND_STRING PROPERTY LINK_FLAGS "-fsanitize=thread ")
 endif()
 
-add_library(libnvim STATIC EXCLUDE_FROM_ALL ${NEOVIM_GENERATED_SOURCES}
-  ${NEOVIM_SOURCES} ${NEOVIM_HEADERS})
+add_library(libnvim STATIC EXCLUDE_FROM_ALL ${NEOVIM_GENERATED_FOR_SOURCES} ${NEOVIM_GENERATED_FOR_HEADERS}
+  ${NEOVIM_GENERATED_SOURCES} ${NEOVIM_SOURCES} ${NEOVIM_HEADERS})
 target_link_libraries(libnvim ${NVIM_LINK_LIBRARIES})
 set_target_properties(libnvim PROPERTIES
   POSITION_INDEPENDENT_CODE ON
   OUTPUT_NAME nvim)
 set_property(TARGET libnvim APPEND_STRING PROPERTY COMPILE_FLAGS " -DMAKE_LIB ")
 
-add_library(nvim-test MODULE EXCLUDE_FROM_ALL ${NEOVIM_GENERATED_SOURCES}
-    ${NEOVIM_SOURCES} ${UNIT_TEST_FIXTURES} ${NEOVIM_HEADERS})
+add_library(nvim-test MODULE EXCLUDE_FROM_ALL ${NEOVIM_GENERATED_FOR_SOURCES} ${NEOVIM_GENERATED_FOR_HEADERS}
+  ${NEOVIM_GENERATED_SOURCES} ${NEOVIM_SOURCES} ${UNIT_TEST_FIXTURES} ${NEOVIM_HEADERS})
 target_link_libraries(nvim-test ${NVIM_LINK_LIBRARIES})
 set_property(TARGET nvim-test APPEND_STRING PROPERTY COMPILE_FLAGS -DUNIT_TESTING)
 
+set(NO_SINGLE_CHECK_HEADERS
+  buffer
+  charset
+  cursor_shape
+  diff
+  digraph
+  ex_cmds
+  ex_getln
+  file_search
+  fold
+  getchar
+  hardcopy
+  if_cscope
+  if_cscope_defs
+  mark
+  mbyte
+  memfile_defs
+  memline
+  memline_defs
+  menu
+  misc2
+  move
+  msgpack_rpc/server
+  ops
+  option
+  os/shell
+  os_unix
+  os/win_defs
+  popupmnu
+  quickfix
+  regexp
+  regexp_defs
+  screen
+  search
+  sha256
+  sign_defs
+  spell
+  syntax
+  syntax_defs
+  tag
+  terminal
+  tui/tui
+  ugrid
+  ui
+  ui_bridge
+  undo
+  undo_defs
+  version
+  window
+)
+foreach(hfile ${NEOVIM_HEADERS})
+  get_filename_component(full_d ${hfile} PATH)
+  file(RELATIVE_PATH d "${PROJECT_SOURCE_DIR}/src/nvim" "${full_d}")
+  if(${d} MATCHES "^[.][.]")
+    file(RELATIVE_PATH d "${GENERATED_DIR}" "${full_d}")
+  endif()
+  get_filename_component(r ${hfile} NAME_WE)
+  if(NOT ${d} EQUAL ".")
+    set(r "${d}/${r}")
+  endif()
+
+  if(NOT ${hfile} MATCHES "[.]c[.]h$")
+    set(tsource "${GENERATED_DIR}/${r}.test-include.c")
+    set(tresult "${GENERATED_DIR}/${r}.test-include.i")
+    string(REPLACE "/" "-" texe "${r}-test")
+    write_file("${tsource}" "#include \"${hfile}\"\nint main(int argc, char **argv) { return 0; }")
+    get_preproc_output(PREPROC_OUTPUT ${tresult})
+    add_executable(
+      ${texe}
+      EXCLUDE_FROM_ALL
+      ${tsource} ${NEOVIM_HEADERS} ${NEOVIM_GENERATED_FOR_HEADERS})
+
+    list(FIND NO_SINGLE_CHECK_HEADERS "${r}" hfile_exclude_idx)
+    if(${hfile_exclude_idx} EQUAL -1)
+      list(APPEND HEADER_CHECK_TARGETS ${texe})
+    endif()
+  endif()
+endforeach()
+add_custom_target(check-single-includes DEPENDS ${HEADER_CHECK_TARGETS})
+
 add_subdirectory(po)
diff --git a/src/nvim/eval_defs.h b/src/nvim/eval_defs.h
index 39028fdb11..8f5e1a897d 100644
--- a/src/nvim/eval_defs.h
+++ b/src/nvim/eval_defs.h
@@ -3,6 +3,7 @@
 
 #include <limits.h>
 #include <stddef.h>
+#include <stdbool.h>
 
 #include "nvim/hashtab.h"
 #include "nvim/lib/queue.h"
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 486baaad47..d1557f9c82 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -67,6 +67,7 @@
 #include "nvim/event/rstream.h"
 #include "nvim/event/wstream.h"
 #include "nvim/shada.h"
+#include "nvim/globals.h"
 
 static int quitmore = 0;
 static int ex_pressedreturn = FALSE;
diff --git a/src/nvim/ex_docmd.h b/src/nvim/ex_docmd.h
index 4def4cbbae..cff350de08 100644
--- a/src/nvim/ex_docmd.h
+++ b/src/nvim/ex_docmd.h
@@ -2,6 +2,7 @@
 #define NVIM_EX_DOCMD_H
 
 #include "nvim/ex_cmds_defs.h"
+#include "nvim/globals.h"
 
 // flags for do_cmdline()
 #define DOCMD_VERBOSE   0x01      // included command in error message
diff --git a/src/nvim/mark.h b/src/nvim/mark.h
index aff6e7273a..efba9708db 100644
--- a/src/nvim/mark.h
+++ b/src/nvim/mark.h
@@ -29,7 +29,7 @@
 
 /// Clear given fmark
 #define CLEAR_FMARK(fmarkp_) \
-    RESET_FMARK(fmarkp_, ((pos_T) {0, 0, 0}), 0)
+    RESET_FMARK(fmarkp_, ((pos_T) { 0, 0, 0 }), 0)
 
 /// Set given extended mark (regular mark + file name)
 #define SET_XFMARK(xfmarkp_, mark_, fnum_, fname_) \
diff --git a/src/nvim/os/fs_defs.h b/src/nvim/os/fs_defs.h
index 0bd9c37750..2277d926b3 100644
--- a/src/nvim/os/fs_defs.h
+++ b/src/nvim/os/fs_defs.h
@@ -14,7 +14,7 @@ typedef struct {
   uint64_t device_id;  ///< @private The id of the device containing the file
 } FileID;
 
-#define FILE_ID_EMPTY (FileID) {.inode = 0, .device_id = 0}
+#define FILE_ID_EMPTY (FileID) { .inode = 0, .device_id = 0 }
 
 typedef struct {
   uv_fs_t request;  ///< @private The request to uv for the directory.
diff --git a/src/nvim/os/os_defs.h b/src/nvim/os/os_defs.h
index 14c210c69c..f81785675e 100644
--- a/src/nvim/os/os_defs.h
+++ b/src/nvim/os/os_defs.h
@@ -27,11 +27,11 @@
 
 // Use up to 5 Mbyte for a buffer.
 #ifndef DFLT_MAXMEM
-# define DFLT_MAXMEM (5*1024)
+# define DFLT_MAXMEM (5 * 1024)
 #endif
 // use up to 10 Mbyte for Vim.
 #ifndef DFLT_MAXMEMTOT
-# define DFLT_MAXMEMTOT (10*1024)
+# define DFLT_MAXMEMTOT (10 * 1024)
 #endif
 
 // Note: Some systems need both string.h and strings.h (Savage).  However,
diff --git a/src/nvim/os/unix_defs.h b/src/nvim/os/unix_defs.h
index c98aa88bfa..5c9daca476 100644
--- a/src/nvim/os/unix_defs.h
+++ b/src/nvim/os/unix_defs.h
@@ -8,7 +8,7 @@
 // POSIX.1-2008 says that NAME_MAX should be in here
 #include <limits.h>
 
-#define TEMP_DIR_NAMES {"$TMPDIR", "/tmp", ".", "~"}
+#define TEMP_DIR_NAMES { "$TMPDIR", "/tmp", ".", "~" }
 #define TEMP_FILE_PATH_MAXLEN 256
 
 #define HAVE_ACL (HAVE_POSIX_ACL || HAVE_SOLARIS_ACL)
diff --git a/src/nvim/os/win_defs.h b/src/nvim/os/win_defs.h
index 8de896c490..827fb2f247 100644
--- a/src/nvim/os/win_defs.h
+++ b/src/nvim/os/win_defs.h
@@ -1,6 +1,10 @@
 #ifndef NVIM_OS_WIN_DEFS_H
 #define NVIM_OS_WIN_DEFS_H
 
+#ifndef WIN32
+# error Header must be included only when compiling for Windows.
+#endif
+
 // winsock2.h must be first to avoid incompatibilities
 // with winsock.h (included by windows.h)
 #include <winsock2.h>
@@ -15,7 +19,7 @@
 
 #define NAME_MAX _MAX_PATH
 
-#define TEMP_DIR_NAMES {"$TMP", "$TEMP", "$USERPROFILE", ""}
+#define TEMP_DIR_NAMES { "$TMP", "$TEMP", "$USERPROFILE", "" }
 #define TEMP_FILE_PATH_MAXLEN _MAX_PATH
 
 #define FNAME_ILLEGAL "\"*?><|"
diff --git a/src/nvim/strings.h b/src/nvim/strings.h
index eb8b83c7d0..8aea374b96 100644
--- a/src/nvim/strings.h
+++ b/src/nvim/strings.h
@@ -1,9 +1,8 @@
 #ifndef NVIM_STRINGS_H
 #define NVIM_STRINGS_H
 
-#include <stdarg.h>
 #include <stdbool.h>
-#include <stddef.h>
+#include <stdarg.h>
 
 #include "nvim/types.h"
 #include "nvim/eval_defs.h"