lisensor

# install from source
cargo install lisensor
# install prebuilt binary with cargo-binstall
cargo binstall lisensor

Lisensor (pronounced licenser) is a tool that automatically adds a license notice to your source file, like this:

// SPDX-License-Identifier: [License]
// Copyright (c) [Year] [Holder]

See https://spdx.dev/learn/handling-license-info/ for more information about this format.

For languages such as python, the comment style will automatically be changed to # instead of //. Languages that do not have either of the comment styles are currently not supported. (Feel free to PR).

Usage

The CLI usage is:

lisensor [CONFIG] ... [-f]

CONFIG is one of more config file for Lisensor (see below). -f will attempt to automatically fix the files in place.

The crate also has a library target of the same name. It's intended to be used by tests in the project, but might be helpful for integrating lisensor into your own tooling.

Config

By default, lisensor looks for Lisensor.toml then lisensor.toml in the current directory if no config files are specified.

Globs in the config file are relative to the directory containing the config file, meaning running lisensor from anywhere will result in the same outcome. Currently, symlinks are not followed.

The config file should contain one table per copyright holder. The table should contain key-value pairs, where the keys are globs (absolute or relative to the directory containing the config file), and the value is any SPDX ID, but the value is not validated.

For example:

["Foobar contributors"]
"**/*.rs" = "MIT"

Inline Config

When the config is small, you can specify it directly in the CLI using the following flags. You cannot use these flags if a config file is specified, or a compatible config is found in the current directory.

lisensor --holder HOLDER --license LICENSE [GLOB_PATTERN] ...

• --holder HOLDER: specify the copyright holder
• --license LICENSE: specify the SPDX ID
• GLOB_PATTERN: specify one or more glob patterns, absolute or resolved from the current directory.

You can only specify one holder and one license type using inline config mode.

Conflict Resolution

If a glob pattern is specified multiple times with a different config, that will be caught and will be reported.

If a file is covered by multiple glob patterns with conflicting configs (such as different copyright holder or different license), check (running without -f) will definitely fail, because it's not possible for one file to satisfy multiple conflicting configs. However, it will not be presented as a conflict, but as a regular license/holder mismatch. The fix mode (running with -f) has an extra check to report an error if a file is covered by conflicting configs. This prevents "fake" successful fixes. However, the fix mode might still edit the file according to one of the configs specified (arbitrarily chosen) before reporting the error.

Compatibility with Other License Notices

It's common if some file is taken from another project, you must include a license notice if it's not already in the file. In this case, it's recommended to use a sentinel line (see Format Behavior Details below) to prevent the tool from accidentally overriding the original notice.

// This file was taken from Foobar project, see original license notices below
// 
// SPDX-License-Identifier: MIT
// Copyright (c) 2025 Other people
// 
// ^ This is bad because running the tool will now
//   change the holder and license into you, even though what you want
//   is to add another notice on top of it

Running the tool will change it to:

// SPDX-License-Identifier: Your License
// Copyright (c) 2025 You

// This file was taken from Foobar project, see original license notices below
// 
// 
// ^ This is bad because running the tool will now
//   change the holder and license into you, even though what you want
//   is to add another notice on top of it

Adding a sentinel line will fix this:

// * * * * *
// This file was taken from Foobar project, see original license notices below
// 
// SPDX-License-Identifier: MIT
// Copyright (c) 2025 Other people
// 
// ^ Now the tool will ignore everything after * * * * *

Now a new notice will be added

// SPDX-License-Identifier: Your License
// Copyright (c) 2025 You
// * * * * *
// This file was taken from Foobar project, see original license notices below
// 
// SPDX-License-Identifier: MIT
// Copyright (c) 2025 Other people
// 
// ^ Now the tool will ignore everything after * * * * *

Format Behavior Details

The tool will check and ensure the following conditions are true for a file:

1. The first line is the license line, with the comment style for that file, and starting with SPDX-License-Identifier: after the comment, followed by the expected license identifier.
2. The second line is the copy right line, with the comment style for that file, and starting with Copyright (c) , follow by a year range, where the start can be anything and the end must be the current year at the local time the tool is ran. If the start and end are the same year, then a single year is sufficient. The year range is followed by a space, then the copyright holder.
3. No other line(s) exist that matches the same SPDX-License-Identifier or Copyright (c) format for license and copyright lines, respectively.

The tool will not attempt fixing the file, if any copyright line is found with the wrong holder. This ensures that the tool never accidentally override license notices from the original source file.

If a source file contains license notice(s) from its original authors, you must specify a sentinel line after your license notice. The tool will skip checking all contents after the sentinel line. The sentinel line is the same comment style followed by * * * * * (five * separated by four spaces). Anything can follow after that. For example:

// SPDX-License-Identifier: MIT
// Copyright (c) 2024-2025 Foobar contributors
// * * * * * other license information below
// SPDX-License-Identifier: MIT
// Copyright (c) 2017-2018 Bizbaz contributors

When the year becomes 2026, the tool will change the notice for Foobar contributors, but will not touch anything below the sentinel line.

Other:

• Line ending:
  • When checking, any line ending is accepted.
  • When fixing, it will turn the file into UNIX line ending.
• When checking, only the first 2 lines are checked, the rest of the file is ignored.
• When fixing, if the third line is not a sentinel line or empty line, it will ensure there's an empty line between the license notice and the rest of the content.