Troubleshooting

Your diagnostic companion for the most common failure modes and confusing situations when using cmakefmt.

cmakefmt Did Not Find The Files I Expected

Check how you invoked it:

• direct file arguments are always processed
• directories are recursively discovered
• discovery respects .cmakefmtignore
• discovery respects .gitignore unless you pass --no-gitignore
• --path-regex filters only discovered paths, not direct file arguments

See exactly what was found and why:

cmakefmt --list-input-files .
cmakefmt --debug --list-input-files .

The Wrong Config File Was Used

Find out exactly what config was selected and what the formatter is actually running with:

cmakefmt --show-config-path path/to/CMakeLists.txt
cmakefmt --show-config path/to/CMakeLists.txt
cmakefmt --explain-config

These commands tell you:

• which config file was selected
• which files were considered
• what CLI overrides changed the final result

A Config Key Was Rejected

cmakefmt deliberately fails fast on unknown config keys instead of silently ignoring them. This is by design — a typo that disappears into a warning is a much worse experience than an immediate error.

Common causes:

• typo in a key name
• using an old draft key name
• confusing commands: (argument structure) with per_command_overrides: (layout/style)

If you are migrating from legacy cmake-format:

cmakefmt --convert-legacy-config .cmake-format.py > .cmakefmt.toml

Then adapt the result to .cmakefmt.yaml if you want YAML as your final format.

Parse Error On Valid-Looking CMake

Run the failing file with full diagnostics:

cmakefmt --debug --check path/to/CMakeLists.txt

cmakefmt should surface:

• file path
• line/column
• source context
• a likely-cause hint when one can be inferred

If the failure is inside a highly custom DSL region, exclude that block temporarily with barrier markers:

# cmakefmt: off
...
# cmakefmt: on

My Custom Command Formats Poorly

This almost always means the command registry does not know the command’s syntax yet.

Add a commands: entry to your config:

commands:
  my_custom_command:
    pargs: 1
    flags:
      - QUIET
    kwargs:
      SOURCES:
        nargs: "+"

Once cmakefmt understands the argument structure, it can produce keyword-aware, properly grouped output instead of flattening everything into a token stream.

If you only want layout or style tweaks for a command whose argument structure cmakefmt already understands, use per_command_overrides: instead.

Stdin Formatting Ignores My Project Config

When formatting stdin, cmakefmt has no real file path and cannot discover config automatically. Fix this with --stdin-path:

cat src/CMakeLists.txt | cmakefmt - --stdin-path src/CMakeLists.txt

The Output Surprises Me

Turn on formatter diagnostics and let cmakefmt explain itself:

cmakefmt --debug path/to/CMakeLists.txt

The debug stream shows:

• which command form was chosen
• which layout family was chosen
• whether barriers or fences were active
• which effective thresholds applied

I Want Quieter CI Logs

cmakefmt --check --quiet .

For machine-readable output that scripts and dashboards can consume:

cmakefmt --check --report-format json .

I Want The Run To Continue After A Bad File

cmakefmt --keep-going --check .

--keep-going lets the formatter process remaining files and print an aggregated summary instead of aborting at the first file-level error. Useful for triage on large repositories.

I Want Safer Rewrites Or Stricter Version Pins

cmakefmt --verify CMakeLists.txt
cmakefmt --required-version 0.3.0 --check .

• --verify reparses the original and formatted output and rejects the run if the parsed CMake semantics change.
• --required-version makes scripts fail fast when the installed binary is not the exact version they expect.
• --in-place already performs semantic verification by default; add --fast only when you explicitly want to skip that extra check.

I Suspect A Performance Regression

Run the benchmark suite:

cargo bench --bench formatter

For one-off workflow timing, compare representative commands with hyperfine. The repository’s full benchmark process is documented in the performance notes.

If the workload is a repeated whole-repo check, also try the built-in cache:

cmakefmt --cache --check .
cmakefmt --cache-location .cache/cmakefmt --cache-strategy content --check .

Use --debug to see detailed cache hit and miss information.

I Want A Gradual Rollout Instead Of Formatting Everything

cmakefmt --require-pragma --check .

Then opt files in explicitly with a top-level marker:

# cmakefmt: enable

Equivalent markers:

• # fmt: enable
• # cmake-format: enable

Files without one of those markers are skipped and show up as skipped=N in the human summary.

Still Stuck?

Open an issue at github.com/cmakefmt/cmakefmt/issues.

When reporting an issue, include:

• the exact command you ran
• the file that failed, or a minimized reproduction
• your .cmakefmt.yaml or .cmakefmt.toml
• the full stderr output
• --debug output when the problem is about formatting behavior rather than a hard parse error