cmake-fmt

Fast CMake formatter with grammar-aware line wrapping and intelligent indentation.

Examples

Line Wrapping & Indentation

Before:

TARGET_LINK_LIBRARIES(myapp PUBLIC Qt6::Core Qt6::Widgets Qt6::Network Boost::system Boost::filesystem PRIVATE spdlog::spdlog fmt::fmt nlohmann_json::nlohmann_json OpenSSL::SSL OpenSSL::Crypto CURL::libcurl)

After:

target_link_libraries(myapp
	PUBLIC
		Qt6::Core
		Qt6::Widgets
		Qt6::Network
		Boost::system
		Boost::filesystem
	PRIVATE
		spdlog::spdlog
		fmt::fmt
		nlohmann_json::nlohmann_json
		OpenSSL::SSL
		OpenSSL::Crypto
		CURL::libcurl
)

Command Casing & Grammar Awareness

Before:

FIND_PACKAGE(Boost REQUIRED COMPONENTS system filesystem thread)
INSTALL(TARGETS myapp mylib RUNTIME DESTINATION bin LIBRARY DESTINATION lib ARCHIVE DESTINATION lib/static)

After:

find_package(Boost REQUIRED COMPONENTS system filesystem thread)
install(TARGETS myapp mylib RUNTIME DESTINATION bin LIBRARY DESTINATION lib ARCHIVE DESTINATION lib/static)

Installation

VS Code Extension

Install from the VS Code Marketplace (coming soon).

Enable format-on-save by adding this to your settings.json:

{
  "[cmake]": {
    "editor.defaultFormatter": "cmake-fmt.cmake-fmt",
    "editor.formatOnSave": true
  }
}

Cargo

cargo install cmake-fmt

Pre-built Binaries

Download pre-built binaries from GitHub Releases (coming soon).

Supported platforms:

• Linux x64
• Linux ARM64
• macOS x64 (Intel)
• macOS ARM64 (Apple Silicon)
• Windows x64
• Windows ARM64

Usage

Format a file to stdout:

cmake-fmt CMakeLists.txt

Format in-place:

cmake-fmt -i CMakeLists.txt

Check if files are formatted (exits with code 1 if changes needed):

cmake-fmt --check CMakeLists.txt

Show formatting diff:

cmake-fmt --diff CMakeLists.txt

Use in CI to enforce formatting:

cmake-fmt --check $(find . -name 'CMakeLists.txt' -o -name '*.cmake')

When going through your files for the first time, you can use --interactive to review changes hunk-by-hunk and choose which ones to apply or skip/disable.

Configuration

cmake-fmt searches for config files upward from the formatted file's directory. Config file names (in priority order):

1. .cmake-fmt (YAML format)
2. .cmake-fmt.yml
3. .cmake-fmt.yaml
4. .cmake-fmt.tml
5. .cmake-fmt.toml

Multiple config files can coexist — root-level defaults are merged with directory-level overrides.

Example Config

indent_width = 2
use_tabs = false
command_case = "lowercase"
max_line_length = 120

Configuration Reference

Setting	Type	Default	Description
disable_format	boolean	false	Skip formatting entirely
indent_width	integer	4	Number of spaces per indent level
max_line_length	integer	80	Max line length (0 = unlimited)
use_tabs	boolean	true	Use tabs for indentation
command_case	enum	lowercase	Built-in command casing: lowercase, uppercase, leave
user_command_case	enum	infer	User-defined command casing: lowercase, uppercase, leave, infer
max_blank_lines	integer	1	Maximum consecutive blank lines allowed
line_ending	enum	auto	Line ending style: auto, lf, crlf
closing_style	enum	remove	Closing statement style: leave, remove, force
force_break_keywords	boolean	false	Always break keywords onto separate lines
final_newline	boolean	true	Ensure file ends with newline
comment_style	enum	hash_space	Comment formatting: leave, hash_space, hash_no_space
source_grouping	enum	none	Group source files: none, headers_first, sources_first
sort_sources	enum	none	Sort source file lists: none, alphabetical

Per-Setting Examples

indent_width

Controls spaces per indentation level (when use_tabs=false).

indent_width = 2:

if(BUILD_TESTING)
  add_subdirectory(tests)
endif()

indent_width = 4 (default):

if(BUILD_TESTING)
    add_subdirectory(tests)
endif()

max_line_length

Controls when lines are wrapped. Setting 0 disables line length limits.

max_line_length = 40:

target_link_libraries(app
	PUBLIC
		Boost::system
		Boost::filesystem
		Qt6::Core
)

max_line_length = 80 (default):

target_link_libraries(app PUBLIC Boost::system Boost::filesystem Qt6::Core)

command_case

Controls casing for built-in CMake commands.

command_case = lowercase (default):

add_executable(myapp main.cpp)
target_link_libraries(myapp PUBLIC Boost::system)

command_case = uppercase:

ADD_EXECUTABLE(myapp main.cpp)
TARGET_LINK_LIBRARIES(myapp PUBLIC Boost::system)

command_case = leave: Preserves original casing from source file.

use_tabs

use_tabs = true (default): Uses tab characters for indentation.

use_tabs = false: Uses spaces for indentation (count controlled by indent_width).

closing_style

Controls whether closing statements like endif() include the condition.

closing_style = remove (default):

if(BUILD_TESTING)
	enable_testing()
endif()

closing_style = force:

if(BUILD_TESTING)
	enable_testing()
endif(BUILD_TESTING)

closing_style = leave: Preserves original closing style from source file.

force_break_keywords

When true, always breaks keywords onto their own lines, even if the command would fit on one line.

force_break_keywords = false (default):

target_link_libraries(app PUBLIC Boost::system)

force_break_keywords = true:

target_link_libraries(app
	PUBLIC
		Boost::system
)

comment_style

Controls comment formatting.

comment_style = hash_space (default): Ensures one space after #:

# This is a comment

comment_style = hash_no_space: Removes space after #:

#This is a comment

comment_style = leave: Preserves original comment formatting.

max_blank_lines

Limits consecutive blank lines. For example, max_blank_lines = 1 (default) allows at most one blank line between statements.

final_newline

When true (default), ensures file ends with a newline character.

disable_format

When true, skips formatting entirely. Useful for temporarily disabling formatting in specific directories via directory-level config.

sort_sources

sort_sources = alphabetical: Sorts file lists in commands like add_executable() alphabetically.

sort_sources = none (default): Preserves original file order.

source_grouping

source_grouping = headers_first: Groups header files (.h, .hpp) before source files (.cpp, .c) in commands like add_executable() but also set() when file lists are detected.

set(SOURCES
    main.h main.cpp
    application.h application.cpp
)

source_grouping = sources_first: Groups source files before header files.

source_grouping = none (default): No grouping applied.

Custom Command Grammars

The command_grammars setting is only available in config files (not via --style). It allows you to define custom command grammars for project-specific CMake functions.

Example .cmake-fmt:

custom_grammer:
  my_custom_command:
    options:
      - VERBOSE
    one_value_keywords:
      - NAME
      - VERSION
    multi_value_keywords:
      - SOURCES
      - HEADERS

For detailed grammar syntax, run:

cmake-fmt --help-grammar

CLI Reference

Flag	Description
-i, --in-place	Format files in-place
--check	Check if files are formatted (exit 1 if changes needed)
--dry-run	Dry run mode (same as --check)
--diff	Show diff of formatting changes
--interactive	Interactive mode: review formatting changes hunk-by-hunk
--style <STYLE>	Override config inline (e.g., "indent_width=4,max_line_length=100")
--export-grammar <FILE>	Export detected custom grammars to a file (scanned from input files)
--export-all-grammar <FILE>	Export all grammars including builtins to a file
--grammar-file <FILE>	Import additional grammar file(s) (can be specified multiple times)
--verbose	Show verbose output during file scanning and analysis
--assume-filename <PATH>	Treat stdin as if formatting this file (resolves config/grammar from its path)
--line-ranges <RANGES>	Format only specific line ranges (e.g., "1:5,10:15")
--help-style	Show all available style settings
--help-grammar	Show grammar file format and keyword types
-h, --help	Print help
-V, --version	Print version

License

MIT — see LICENSE for details.