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Add a new language

Dolos is built on top of a generic parser model to achieve loose coupling with specific programming languages. As a result, it is fairly easy to add support for additional programming languages if a suitable parser is available.

Dolos bundles officially supported parsers in the dolos-parsers module. Let us know if you want to use a language that is not supported yet.

In addition, Dolos can automatically discover available Tree-sitter parsers on the local system at runtime. As such, if you are running Dolos locally, you can quickly add support for a new language by installing a Tree-sitter parser for that language in the node_modules on your system (Dolos searches NODE_PATH).

As an example, we demonstrate how the Rust programming language can be supported.

Check availability

To assure that Dolos does not yet support the target programming language, simply run:

dolos -l rust *.rs

If no parser is available for the target language, you'll get this error message:

[error] Error: No tokenizer found for rust

Find a parser

If no parser is available for the target programming language, search an appropriate parser on the Tree-sitter website or on the Tree-sitter GitHub page.

There exists a Rust parser named tree-sitter-rust.


If the language you are looking for is not listed on either the website or GitHub, it might be that there is no parser available. If that is the case, you can contact us and we will see if we can help.

It is possible to create a new parser, but this quickly becomes complicated.

Install the parser

First run the command dolos --version to check what version of Tree-sitter is currently used by Dolos. The output will look like this:

Dolos v2.2.3
Node v18.16.0
Tree-sitter v0.20.1

Tree-sitter parsers must have the same (major) version as the core library, so the version must be specified explicitly by suffixing the parser name with @<version>. Dolos uses Tree-sitter v0.20.0 in the above example above, so we need to install tree-sitter-rust@0.20 in that case. You may safely omit the minor version (the third number after the final dot).

Use npm to install a Tree-sitter parser for a specific programming language:

npm install -g tree-sitter-rust@0.20

Start Dolos with the new parser

Dolos automatically detects newly installed parsers as soon as a new analysis is run.

Contact us on GitHub if you need help with supporting additional programming languages.

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