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https://github.com/github/semantic

Parsing, analyzing, and comparing source code across many languages
https://github.com/github/semantic

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Parsing, analyzing, and comparing source code across many languages

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README 

        
# Semantic



`semantic` is a Haskell library and command line tool for parsing, analyzing, and comparing source code.



In a hurry? Check out our documentation of [example uses for the `semantic` command line tool](docs/examples.md).



| Table of Contents |

| :------------- |

| [Usage](#usage) |

| [Language support](#language-support) |

| [Development](#development) |

| [Technology and architecture](#technology-and-architecture) |

| [Licensing](#licensing) |



## Usage



Run `semantic --help` for complete list of up-to-date options.



#### Parse

```

Usage: semantic parse [--sexpression | (--json-symbols|--symbols) |

                        --proto-symbols | --show | --quiet] [FILES...]

  Generate parse trees for path(s)



Available options:

  --sexpression            Output s-expression parse trees (default)

  --json-symbols,--symbols Output JSON symbol list

  --proto-symbols          Output protobufs symbol list

  --show                   Output using the Show instance (debug only, format

                           subject to change without notice)

  --quiet                  Don't produce output, but show timing stats

  -h,--help                Show this help text

   ```



## Language support



| Language       | Parse | AST Symbols† | Stack graphs |

| :------------- | :---: | :---:        | :---:        |

| Ruby           | ✅    | ✅           | |

| JavaScript     | ✅    | ✅           | |

| TypeScript     | ✅    | ✅           | 🚧 |

| Python         | ✅    | ✅           | 🚧 |

| Go             | ✅    | ✅           | |

| PHP            | ✅    | ✅           | |

| Java           | 🚧    | ✅           | |

| JSON           | ✅    | ⬜️           | ⬜️ |

| JSX            | ✅    | ✅           | |

| TSX            | ✅    | ✅           | |

| CodeQL         | ✅    | ✅           | |

| Haskell        | 🚧    | 🚧           | |



† Used for [code navigation](https://help.github.com/en/github/managing-files-in-a-repository/navigating-code-on-github) on github.com.

* ✅ — Supported

* 🔶 — Partial support

* 🚧 — Under development

* ⬜ - N/A ️



## Development



`semantic` requires at least GHC 8.10.1 and Cabal 3.0. We strongly recommend using [`ghcup`][ghcup] to sandbox GHC versions, as GHC packages installed through your OS's package manager may not install statically-linked versions of the GHC boot libraries. `semantic` currently builds only on Unix systems; users of other operating systems may wish to use the [Docker images](https://github.com/github/semantic/packages/11609).



We use `cabal's` [Nix-style local builds][nix] for development. To get started quickly:



```bash

git clone [email protected]:github/semantic.git

cd semantic

script/bootstrap

cabal v2-build all

cabal v2-run semantic:test

cabal v2-run semantic:semantic -- --help

```



You can also use the [Bazel](https://bazel.build) build system for development. To learn more about Bazel and why it might give you a better development experience, check the [build documentation](docs/build.md).



``` bash

git clone [email protected]:github/semantic.git

cd semantic

script/bootstrap-bazel

bazel build //...

```



 `stack` as a build tool is not officially supported; there is [unofficial `stack.yaml` support](https://github.com/jkachmar/semantic-stack-yaml) available, though we cannot make guarantees as to its stability.



[nix]: https://cabal.readthedocs.io/en/3.4/nix-local-build-overview.html

[ghcup]: https://www.haskell.org/ghcup/



## Technology and architecture



Architecturally, `semantic`:

1. Generates per-language Haskell syntax types based on [tree-sitter](https://github.com/tree-sitter/tree-sitter) grammar definitions.

2. Reads blobs from a filesystem or provided via a protocol buffer request.

3. Returns blobs or performs analysis.

4. Renders output in one of many supported formats.



Throughout its lifecycle, `semantic` has leveraged a number of interesting algorithms and techniques, including:



- Myers' algorithm (SES) as described in the paper [*An O(ND) Difference Algorithm and Its Variations*][SES]

- RWS as described in the paper [*RWS-Diff: Flexible and Efficient Change Detection in Hierarchical Data*][RWS].

- Open unions and [data types à la carte](http://www.cs.ru.nl/~W.Swierstra/Publications/DataTypesALaCarte.pdf).

- An implementation of [Abstracting Definitional Interpreters][adi] extended to work with an à la carte representation of syntax terms.



[SES]: http://www.xmailserver.org/diff2.pdf

[RWS]: https://db.in.tum.de/~finis/papers/RWS-Diff.pdf

[adi]: https://plum-umd.github.io/abstracting-definitional-interpreters/

[tree-sitter]: https://github.com/tree-sitter/tree-sitter



## Contributions



Contributions are welcome!  Please see our [contribution

guidelines](CONTRIBUTING.md) and our [code of conduct](CODE_OF_CONDUCT.md) for

details on how to participate in our community.



## Licensing



Semantic is licensed under the [MIT license](semantic/LICENSE).