jscpd for VS Code

Copy/paste detection while you type. The extension runs jscpd as a language server, so every clone, dead symbol or over-complex function shows up as a diagnostic in the file you are editing, with a gutter icon colored by kind, a code action that jumps to the other copy, and four views in the jscpd side bar.

loans.js with a hover on a copied function, the jscpd side bar and the Problems panel

What you get

Clones as you edit. Exact copies, renamed copies (same code, other identifiers), near-miss copies, functions with the same syntax-tree shape, and, with the embedding model, functions that do the same job in different code. Each kind has its own color and gutter icon.
Code actions on a clone: go to the other copy, or wrap the block in jscpd:ignore-start / jscpd:ignore-end.
Dead code (unused files, exports, symbols, imports and members) and complexity (functions and files over the limit), when you turn them on.
The jscpd side bar: Clones grouped by kind, Dead code by category, Complexity by file, and Migration for a port.
A status bar item with the duplication of the open projects.
Migration: pick the folder you port from and the folder you port to, and jscpd --compare pairs their functions. The view lists every paired function with its similarity, the functions that are still only on one side, and the ones that are ready to port. The HTML map opens next to your code and refreshes when you save a file in either folder.

With dead code on, an export that no file imports fades out, and the hover gives the confidence of the finding:

formatFine in format.js, faded, with the hover of the unused export

This is fixtures/compare-demo after jscpd: Compare two folders, with the Python module as the source and its TypeScript port as the target:

The migration map of compare-demo next to the Migration view

Install

Install jscpd from the VS Code Marketplace or Open VSX.
The extension looks for jscpd in PATH. If it is not there it offers to download the release build for your platform from GitHub, checks it against the release's checksums.txt, and keeps it in the extension's storage. You can also point jscpd.path at a binary you installed yourself (npm i -g jscpd, cargo install jscpd, Homebrew, or the installer on jscpd.dev).

jscpd 5.4.0 or newer is needed for the language server.

Settings

Setting	Default	What it does
`jscpd.enable`	`true`	Start jscpd for the workspace.
`jscpd.path`	`""`	Path to the executable. Empty: look in `PATH`, then use or download a release.
`jscpd.download`	`ask`	`ask`, `always` or `never` download a release when nothing is installed.
`jscpd.version`	`latest`	The release to download, `latest` or a tag.
`jscpd.analyses.clones`	`true`	Exact, renamed and near-miss copies.
`jscpd.analyses.similarFunctions`	`false`	Functions with the same syntax-tree shape (JavaScript, TypeScript). Off: as the project says.
`jscpd.analyses.semantic`	`false`	Semantic clones through the embedding model. Off: as the project says.
`jscpd.analyses.deadCode`	`false`	Unused files, exports, symbols, imports and members. Off: as the project says.
`jscpd.analyses.complexity`	`false`	Functions and files over the complexity limit. Off: as the project says.
`jscpd.allFiles`	`false`	Publish diagnostics for closed files too, so the Problems panel lists the whole project.
`jscpd.clones.warningTokens`	`null`	Clones of at least this many tokens are warnings, smaller ones information.
`jscpd.similarFunctions.similarity`	`0.85`	How much shape two functions must share.
`jscpd.complexity.functionLimit`	`15`	Cyclomatic complexity above which a function gets a diagnostic.
`jscpd.settings`	`{}`	Keys of `.jscpd.json` applied on top of every project's own config.
`jscpd.args`	`[]`	Extra arguments for `jscpd --lsp`.
`jscpd.decorations`	`true`	Gutter icons and overview-ruler marks.
`jscpd.compare.ignore`	vendored folders	Globs `--compare` leaves out of both sides.
`jscpd.compare.watch`	`true`	Run the last comparison again on save.
`jscpd.trace.server`	`off`	Log the LSP traffic.

Each project keeps its own .jscpd.json; the server reads it, and the lsp section of that file sets the same analyses per project. The settings above are merged on top for all open projects, and only what you switch is sent: an analysis left off in the editor runs when the project turns it on, and values at their defaults leave the project's own in place.

Commands

jscpd: Rescan the workspace, jscpd: Restart the language server, jscpd: Show server output, jscpd: Download or update the jscpd binary, jscpd: Compare two folders (measure a port), jscpd: Run the last comparison again, jscpd: Open the migration map.

Try it

Open fixtures/lsp-demo from the jscpd-ide repository. src/loans.js holds one function copied into holds.js, one built like a function in holds.js, and one with 19 branches; the README of the fixture says which diagnostic each gets. fixtures/compare-demo has a Python module and its TypeScript port for the Migration view. The screenshots above come from these two fixtures.

Development

cd vscode
npm install
npm run build        # or npm run watch
npm test             # downloads VS Code and runs the suite against fixtures/lsp-demo
npm run package      # writes jscpd-<version>.vsix

Press F5 in VS Code to open an extension host on the fixture.

jscpd

Andrey Kucherenko