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.
| Table of Contents |
|---|
| Usage |
| Language support |
| Development |
| Technology and architecture |
| Licensing |
Usage
Run semantic --help for complete list of up-to-date options.
Parse
Usage: semantic parse ([--sexpression] | [--json] | [--json-graph] | [--symbols]
| [--dot] | [--show] | [--quiet]) [FILES...]
Generate parse trees for path(s)
Available options:
--sexpression Output s-expression parse trees (default)
--json Output JSON parse trees
--json-graph Output JSON adjacency list
--symbols Output JSON symbol list
--dot Output DOT graph parse trees
--show Output using the Show instance (debug only, format
subject to change without notice)
--quiet Don't produce output, but show timing stats
Diff
Usage: semantic diff ([--sexpression] | [--json] | [--json-graph] | [--toc] |
[--dot] | [--show]) [FILE_A] [FILE_B]
Compute changes between paths
Available options:
--sexpression Output s-expression diff tree (default)
--json Output JSON diff trees
--json-graph Output JSON diff trees
--toc Output JSON table of contents diff summary
--dot Output the diff as a DOT graph
--show Output using the Show instance (debug only, format
subject to change without notice)
Graph
Usage: semantic graph ([--imports] | [--calls]) [--packages] ([--dot] | [--json]
| [--show]) ([--root DIR] [--exclude-dir DIR]
DIR:LANGUAGE | FILE | --language ARG (FILES... | --stdin))
Compute a graph for a directory or from a top-level entry point module
Available options:
--imports Compute an import graph (default)
--calls Compute a call graph
--packages Include a vertex for the package, with edges from it
to each module
--dot Output in DOT graph format (default)
--json Output JSON graph
--show Output using the Show instance (debug only, format
subject to change without notice)
--root DIR Root directory of project. Optional, defaults to
entry file/directory.
--exclude-dir DIR Exclude a directory (e.g. vendor)
--language ARG The language for the analysis.
--stdin Read a list of newline-separated paths to analyze
from stdin.
Language support
| Priority | Language | Parse | Assign | Diff | ToC | Symbols | Import graph | Call graph | Control flow graph |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Ruby | ||||||||
| 2 | JavaScript | ||||||||
| 3 | TypeScript | ||||||||
| 4 | Python | ||||||||
| 5 | Go | ||||||||
| PHP | |||||||||
| Java | N/A | ||||||||
| JSON | N/A | N/A | N/A | N/A | N/A | ||||
| Java | |||||||||
| JSX | |||||||||
| Haskell | |||||||||
| Markdown | N/A | N/A | N/A |
✅ — Supported🔶 — Partial support🚧 — Under development
Development
semantic requires at least GHC 8.8.1 and Cabal 3.0. We strongly recommend using 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.
We use cabal's Nix-style local builds for development. To get started quickly:
git clone git@github.com:github/semantic.git
cd semantic
script/bootstrap
cabal v2-build
cabal v2-test
cabal v2-run semantic -- --helpstack as a build tool is not officially supported; there is an unofficial stack.yaml available, though we cannot make guarantees as to its stability.
Technology and architecture
Architecturally, semantic:
- Reads blobs.
- Generates parse trees for those blobs with tree-sitter (an incremental parsing system for programming tools).
- Assigns those trees into a generalized representation of syntax.
- Performs analysis, computes diffs, or just returns parse trees.
- Renders output in one of many supported formats.
Semantic leverages a number of interesting algorithms and techniques:
- Myers' algorithm (SES) as described in the paper An O(ND) Difference Algorithm and Its Variations
- RWS as described in the paper RWS-Diff: Flexible and Efficient Change Detection in Hierarchical Data.
- Open unions and data types à la carte.
- An implementation of Abstracting Definitional Interpreters extended to work with an à la carte representation of syntax terms.
Contributions
Contributions are welcome! Please see our contribution guidelines and our code of conduct for details on how to participate in our community.
Licensing
Semantic is licensed under the MIT license.