whitespace-format

Linter and formatter of whitespace in source code files and text files.

The purpose of this tool is to normalize whitespace in source code files (e.g., Python, Java, C/C++, JavaScript, Rust, Go, Ruby, SQL, Bash) and text files (HTML, CSS, JSON, YAML, CSV, TSV MarkDown, LaTeX). This is useful when sharing the code with other people; for example, before the files are checked into a version control system.

The features include:

• Remove whitespace at the end of each line.
• Remove empty lines at the end of the file.
• Remove empty lines at the beginning of the file.
• Add a new line marker at the end of the file if it is missing.
• Auto-detection of new line markers (Linux \n, Windows \r\n, Mac \r).
• Make new line markers consistent.
• Replace tabs with spaces.
• Remove/replace non-standard whitespace characters.

The formatting changes are idempotent, i.e., running the tool a second time (with the same parameters) has no effect.

Currently, the tool assumes that the files are encoded in either UTF-8, ASCII or Extended ASCII. The results on other types of files are undefined.

The tool is implemented in Rust. This ensures the necessary speed to handle many and/or large files. For example, formatting the whole Linux Kernel code base (1.4 GB, 87k files, 4k modified files) on a modern computer takes less than 3 seconds.

Installation

Installation using cargo

The package is published to crates.io. If you have cargo installed, you can install the package by running:

cargo install whitespace-format

Debian package

If you are using a Debian-based system (Ubuntu, Debian, Mint, etc.), you can download the Debian package from the release page and install it using dpkg with the command:

sudo dpkg --install whitespace-format*.deb

Usage

A sample command that formats source code files:

whitespace-format \
    --exclude "\.git/|\.idea/|\.pyc$" \
    --new-line-marker linux \
    --normalize-new-line-markers \
    foo.txt  my_project/

The command above formats foo.txt and all files contained in my_project/ directory and its subdirectories. Files that contain .git/ or .idea/ in their (relative) path are excluded. For example, files in my_project/.git/ and files in my_project/.idea/ are excluded. Likewise, files ending with .pyc are excluded.

If you want to know only if any files need to be formatted and what changes need to be made, add --check-only option:

whitespace-format \
    --check-only \
    --exclude "\.git/|\.idea/|\.pyc$" \
    --new-line-marker linux \
    --normalize-new-line-markers \
    foo.txt  my_project/

If any of the files needs to be formatted, the command exits with a non-zero exit code. The command prints list of any changes that need to be made to each file. The command can be used as a validation step before checking the source files into a version control system (e.g. as a pre-commit or a pre-submit check), or as a test running before the code is merged into the main branch.

Options

• --check-only -- Do not format files. Only report which files need to be formatted and what changes need to be made to each file. If one or more files need to be formatted, a non-zero exit code is returned.
• --follow-symlinks -- Follow symbolic links when searching for files.
• --exclude=REGEX -- Regular expression that specifies which files to exclude. The regular expression is evaluated on the path of each file. For example, --exclude="(\.jpeg|\.png)$" excludes files with .jpeg or .png extension. As another example, --exclude="^tmp/" excludes all files in the top-level tmp/ directory and its subdirectories, however, files in data/tmp/ will not be excluded.
• --color=MODE -- This options specifies color output:
  • auto -- Determine whether to enable color output automatically based on the terminal used.
  • on -- Turn on color output.
  • off -- Turn off color output.

Formatting options

• --new-line-marker=MARKER -- Specifies what new line marker to use in the formatted output file. MARKER must be one of the following:
  • auto -- Use new line marker that is the most common in each individual file. If no new line marker is present in the file, Linux \n is used. This is the default option.
  • linux -- Use Linux new line marker \n.
  • mac -- Use Mac new line marker \r.
  • windows -- Use Windows new line marker \r\n.
• --normalize-new-line-markers -- Make new line markers consistent in each file by replacing \r\n, \n, and \r with a consistent new line marker. The new line marker in the output is specified by --new-line-marker option. This option works even if the input contains an arbitrary mix of new line markers \r\n, \n, \r even within the same input file.
• --add-new-line-marker-at-end-of-file -- Add new line marker at the end of each file if it is missing.
• --remove-new-line-marker-from-end-of-file -- Remove all new line marker(s) from the end of each file. Due to idempotence, all empty lines at the end of the file are removed. In other words, --remove-new-line-marker-from-end-of-file implies --remove-trailing-empty-lines option. The option --remove-new-line-marker-from-end-of-file conflicts with --add-new-line-marker-at-end-of-file option.
• --remove-trailing-whitespace -- Remove whitespace at the end of each line.
• --remove-leading-empty-lines -- Remove empty lines at the beginning of each file.
• --remove-trailing-empty-lines -- Remove empty lines at the end of each file. If --remove-new-line-marker-from-end-of-file is used, --remove-trailing-empty-lines is used as well; otherwise the behavior would not be idempotent.

An opinionated combination of options is:

whitespace-format \
    --new-line-marker=linux \
    --add-new-line-marker-at-end-of-file \
    --normalize-new-line-markers \
    --remove-trailing-whitespace \
    --remove-leading-empty-lines \
    --remove-trailing-empty-lines \
    foo.txt  my_project/

This combination should work well for common programming languages (e.g., Python, Java, C/C++, JavaScript, Rust, Go, Ruby, SQL, Bash) and common text file formats (e.g., HTML, CSS, CSV, TSV, JSON, YAML, MarkDown, Makefile, LaTeX).

Empty files

The options above do not format empty files and files consisting of only whitespace. There are separate options for handling such files:

• --normalize-empty-files=MODE
• --normalize-whitespace-only-files=MODE

where MODE is one of the following:

• ignore -- Leave the file unchanged. This is the default option.
• empty -- Replace the file with an empty file.
• one-line -- Replace the file with a file consisting of a single new line marker.

Depending on the mode, an empty file or a whitespace-only file will be either ignored, replaced by a zero-byte file, or replaced by a file consisting of the single new line marker.

The options --normalize-empty-files=ignore and --normalize-empty-files=empty are identical.

If --normalize-whitespace-only-files is set to empty, --normalize-empty-files is set to empty as well. In other words, combination --normalize-whitespace-only-files=empty and --normalize-empty-files=one-line is not allowed, since it would lead to behavior that is not idempotent.

An opinionated combination for these two options is:

whitespace-format \
    ...
    --normalize-empty-files=empty \
    --normalize-whitespace-only-files=empty

This combination should work well for common programming languages (e.g., Python, Java, C/C++, JavaScript, Rust, Go, Ruby, SQL, Bash) and common text file formats (e.g., HTML, CSS, CSV, TSV, JSON, YAML, MarkDown, Makefile, LaTeX).

Special characters

• --replace-tabs-with-spaces=N -- Remove tabs or replace them with spaces. The value N specifies the number of spaces to use. If N is positive each tab character is replaced by N spaces. If N is zero, tabs are removed. If N is negative, tabs are left unchanged. Default value is -1.

• --normalize-non-standard-whitespace=MODE -- Replace or remove non-standard whitespace characters (\v and \f). MODE must be one of the following:

  • ignore -- Leave \v and \f as is. This is the default option.
  • replace -- Replace any occurrence of \v or \f with a single space.
  • remove -- Remove all occurrences of \v and \f

It is recommended to avoid tabs in source code and text files if possible, and replace them with spaces or other strings, such as \t or 	. While both tabs and spaces are functionally similar for indentation in text files, using spaces offers consistency in how the indentation appears across different editors and platforms, as a space character always renders as a single space. Tabs, on the other hand, can be configured to represent a varying number of spaces in different editors, potentially leading to inconsistent visual formatting if not everyone working on the code uses the same tab settings.

If --check-only is used, a combination of non-default options is recommended (e.g. --replace-tabs-with-spaces=0 and --normalize-non-standard-whitespace=remove). This will warn about presence of tabs and non-standard whitespace characters. However, Makefiles and TSV files must be explicitly excluded using the --exclude option.

However, without --check-only, there is no simple universal recommendation for all text files. First, in Makefiles and TSV files, tabs are required. Second, even in programming languages and text data formats where tabs can be avoided (e.g. Python, Java, C/C++), their replacement depends on the context. For example, in Python, Java and C/C++, tabs in string literals can be replaced by the string \t. However, tabs outside of string literals cannot be replaced by the string \t and instead spaces must be used. While it is possible to replace tabs by spaces in string literals, this changes the semantics of the program.

License

MIT