build(lint): fix luacheck not found #18940

Problem:
Since 6d57bb89c1 #18543, luacheck is not found on some systems when
running the "lintlua" target.

Solution:
- Move the find_program() to the top-level CMakeLists.txt
- Define a def_cmd_target() function with fewer assumptions than the old
  lint() function.
- Move "lintuncrustify" to src/nvim/CMakeLists.txt so it can reuse the
  $LINT_NVIM_SOURCES already defined there.
- Make the lint targets _fatal_ by default. There is little reason for
  the "lint" umbrella target defined in Makefile to exist if it's going
  to ignore the absence of the actual linters.
- For now, keep the uncrustify call in a separate cmake script so that
  it can be silenced (too noisy).

CMakeLists.txt

@@ -612,6 +612,33 @@ if(NOT BUSTED_OUTPUT_TYPE)
   set(BUSTED_OUTPUT_TYPE "nvim")
 endif()
 
+#
+# Lint
+#
+find_program(LUACHECK_PRG luacheck)
+find_program(STYLUA_PRG stylua)
+find_program(FLAKE8_PRG flake8)
+find_program(UNCRUSTIFY_PRG uncrustify)
+find_program(SHELLCHECK_PRG shellcheck)
+include(DefCmdTarget)
+def_cmd_target(lintlua ${LUACHECK_PRG} LUACHECK_PRG true)
+if(LUACHECK_PRG)
+  add_custom_command(OUTPUT lintlua-cmd APPEND COMMAND ${LUACHECK_PRG} -q runtime/ scripts/ src/ test/)
+endif()
+if(STYLUA_PRG)
+  add_custom_command(OUTPUT lintlua-cmd APPEND COMMAND ${STYLUA_PRG} --color=always --check runtime/)
+else()
+  add_custom_command(OUTPUT lintlua-cmd APPEND COMMAND ${CMAKE_COMMAND} -E echo "STYLUA_PRG not found")
+endif()
+def_cmd_target(lintpy ${FLAKE8_PRG} FLAKE8_PRG true)
+if(FLAKE8_PRG)
+  add_custom_command(OUTPUT lintpy-cmd APPEND COMMAND ${FLAKE8_PRG} contrib/ scripts/ src/ test/)
+endif()
+def_cmd_target(lintsh ${SHELLCHECK_PRG} SHELLCHECK_PRG true)
+if(SHELLCHECK_PRG)
+  add_custom_command(OUTPUT lintsh-cmd APPEND COMMAND ${SHELLCHECK_PRG} scripts/vim-patch.sh)
+endif()
+
 include(InstallHelpers)
 
 file(GLOB MANPAGES
@@ -745,14 +772,6 @@ if(BUSTED_LUA_PRG)
     set_target_properties(functionaltest-lua PROPERTIES FOLDER test)
 endif()
 
-foreach(TARGET IN ITEMS lintlua lintsh lintpy lintuncrustify)
-  add_custom_target(${TARGET}
-    COMMAND ${CMAKE_COMMAND}
-    -DPROJECT_ROOT=${PROJECT_SOURCE_DIR}
-    -DTARGET=${TARGET}
-    -P ${PROJECT_SOURCE_DIR}/cmake/lint.cmake)
-endforeach()
-
 #add uninstall target
 if(NOT TARGET uninstall)
     configure_file(

cmake/DefCmdTarget.cmake

@@ -0,0 +1,27 @@
+# Defines a target named ${target} and a command with (symbolic) output
+# ${target}-cmd. If ${prg} is undefined the target prints "not found".
+#
+# - Use add_custom_command(…APPEND) to build the command after this.
+# - Use add_custom_target(…DEPENDS) to run the command from a target.
+function(def_cmd_target target prg prg_name prg_fatal)
+  # Define a mostly-empty command, which can be appended-to.
+  add_custom_command(OUTPUT ${target}-cmd
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+      COMMAND ${CMAKE_COMMAND} -E echo "${target}"
+  )
+  # Symbolic (does not generate an artifact).
+  set_source_files_properties(${target}-cmd PROPERTIES SYMBOLIC "true")
+
+  if(prg OR NOT prg_fatal)
+    add_custom_target(${target}
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+      DEPENDS ${target}-cmd)
+    if(NOT prg)
+      add_custom_command(OUTPUT ${target}-cmd APPEND
+        COMMAND ${CMAKE_COMMAND} -E echo "${target}: SKIP: ${prg_name} not found")
+    endif()
+  else()
+    add_custom_target(${target} false
+      COMMENT "${target}: ${prg_name} not found")
+  endif()
+endfunction()

cmake/RunUncrustify.cmake

@@ -0,0 +1,5 @@
+# HACK: This script is invoked with "cmake -P …" as a workaround to silence uncrustify.
+
+execute_process(
+  COMMAND ${UNCRUSTIFY_PRG} -c "${PROJECT_SOURCE_DIR}/src/uncrustify.cfg" -q --check ${LINT_NVIM_SOURCES}
+  OUTPUT_QUIET)

cmake/lint.cmake

@@ -1,34 +0,0 @@
-function(lint)
-  cmake_parse_arguments(LINT "QUIET" "PROGRAM" "FLAGS;FILES" ${ARGN})
-
-  if(LINT_QUIET)
-    set(OUTPUT_QUIET OUTPUT_QUIET)
-  elseif()
-    set(OUTPUT_QUIET "")
-  endif()
-
-  find_program(PROGRAM_EXISTS ${LINT_PROGRAM})
-  if(PROGRAM_EXISTS)
-    execute_process(COMMAND ${LINT_PROGRAM} ${LINT_FLAGS} ${LINT_FILES}
-      WORKING_DIRECTORY ${PROJECT_ROOT}
-      RESULT_VARIABLE ret
-      ${OUTPUT_QUIET})
-    if(ret AND NOT ret EQUAL 0)
-      message(FATAL_ERROR "FAILED: ${TARGET}")
-    endif()
-  else()
-    message(STATUS "${TARGET}: ${LINT_PROGRAM} not found. SKIP.")
-  endif()
-endfunction()
-
-if(${TARGET} STREQUAL "lintuncrustify")
-  file(GLOB_RECURSE FILES ${PROJECT_ROOT}/src/nvim/*.[c,h])
-  lint(PROGRAM uncrustify FLAGS -c src/uncrustify.cfg -q --check FILES ${FILES} QUIET)
-elseif(${TARGET} STREQUAL "lintpy")
-  lint(PROGRAM flake8 FILES contrib/ scripts/ src/ test/)
-elseif(${TARGET} STREQUAL "lintsh")
-  lint(PROGRAM shellcheck FILES scripts/vim-patch.sh)
-elseif(${TARGET} STREQUAL "lintlua")
-  lint(PROGRAM luacheck FLAGS -q FILES runtime/ scripts/ src/ test/)
-  lint(PROGRAM stylua FLAGS --color=always --check FILES runtime/)
-endif()

src/nvim/CMakeLists.txt

@@ -1,5 +1,7 @@
 option(USE_GCOV "Enable gcov support" OFF)
 
+include(DefCmdTarget)
+
 if(USE_GCOV)
   if(CLANG_TSAN)
     # GCOV and TSAN results in false data race reports
@@ -802,12 +804,22 @@ foreach(sfile ${LINT_NVIM_SOURCES})
 endforeach()
 add_custom_target(lintc DEPENDS ${LINT_TARGETS})
 
+def_cmd_target(lintuncrustify ${UNCRUSTIFY_PRG} UNCRUSTIFY_PRG false)  # Non-fatal so that "lintc" target can depend on it.
+if(UNCRUSTIFY_PRG)
+  add_custom_command(OUTPUT lintuncrustify-cmd APPEND
+    COMMAND ${CMAKE_COMMAND}
+      -DUNCRUSTIFY_PRG=${UNCRUSTIFY_PRG}
+      -DPROJECT_SOURCE_DIR=${PROJECT_SOURCE_DIR}
+      -DLINT_NVIM_SOURCES=${LINT_NVIM_SOURCES}
+      -P ${PROJECT_SOURCE_DIR}/cmake/RunUncrustify.cmake)
+endif()
+
 add_custom_target(
   lintcfull
   COMMAND
     ${LINT_PRG} --suppress-errors=${LINT_SUPPRESS_FILE} ${LINT_NVIM_REL_SOURCES}
   WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
-  DEPENDS ${LINT_PRG} ${LINT_NVIM_SOURCES} ${LINT_SUPPRESS_FILE}
+  DEPENDS ${LINT_PRG} ${LINT_NVIM_SOURCES} ${LINT_SUPPRESS_FILE} lintuncrustify
 )
 
 add_custom_target(generated-sources DEPENDS