Clojure DAP
Debug Adapter Protocol support for Clojure inside VS Code, backed by clojure-dap and CIDER's nREPL debug middleware. Set breakpoints, step through code, evaluate expressions, inspect locals and stacks — driven from your existing nREPL session.
The extension is a thin client. clojure-dap is a standalone JVM that connects to your existing nREPL — start that however you like (Conjure, Calva, lein repl, clj with CIDER middleware, mise dev, etc.) so it writes .nrepl-port to your project root, and the DAP server picks the port up automatically. Or pass host/port explicitly in launch.json.
Prerequisites
- A running nREPL server with CIDER middleware
- Java 21+ and Clojure CLI on the launched command's path
Settings
| Setting |
Default |
Purpose |
clojure-dap.command |
clojure |
Executable launched as the DAP server. Set to an absolute path if your clojure binary isn't on the GUI PATH (mise/asdf users) or to a wrapper that activates project tooling. |
clojure-dap.args |
["-Sdeps", "{:deps {uk.me.oli/clojure-dap {:mvn/version \"RELEASE\"}}}", "-X", "clojure-dap.main/run"] |
Arguments passed to the launch command. Override the :mvn/version to pin a specific clojure-dap release. |
Edit them from Settings → Extensions → Clojure DAP and scope to the project via the Workspace tab — workspace settings land in .vscode/settings.json so a team can share them.
Launch configuration
Use the bundled "Clojure DAP: Attach to nREPL" snippet, or add to launch.json:
{
"type": "clojure-dap",
"request": "attach",
"name": "Attach to nREPL"
}
By default the DAP server connects to 127.0.0.1 and reads the port from .nrepl-port. You can pass explicit connection options:
{
"type": "clojure-dap",
"request": "attach",
"name": "Attach to nREPL",
"clojure_dap": {
"type": "nrepl",
"nrepl": { "host": "127.0.0.1", "port": 7888 }
}
}
Keep stdout clean
The launched process talks to VS Code over stdio using DAP's JSON-RPC framing protocol. The default invocation is safe; if you wrap clojure in your own clojure-dap.command script, make sure the wrapper itself doesn't print banners, status lines, or its own logs to stdout — anything not in the DAP frame format will corrupt the transport.
Usage
- Start your nREPL server with CIDER middleware
- Set breakpoints in your editor
- Run "Attach to nREPL" from the debug panel
- Trigger the breakpointed code from a REPL
- Inspect variables, evaluate expressions, step through code
See also
License
Released into the public domain via the Unlicense.
