Awesome

Grenchman

Fast invocation of Clojure code over nREPL.

To install, download the appropriate binary from https://leiningen.org/grench.html and place it on your path. If downloads for your platform are not provided you can compile your own; see "Building" below.

Usage

Grenchman has five main commands:

grench eval "(+ 12 49)" - evals given form
grench main my.main.ns/entry-point arg1 arg2 - runs existing defn
grench repl or grench repl :connect $PORT - connects a repl
grench load path/to/file.clj - load a file
grench lein test - runs a Leiningen task

Running with no arguments will read code from stdin to accomodate shebangs.

The first four commands connect to a running nREPL project server in order to avoid JVM startup time. The simplest way to start a project nREPL server is to run lein trampoline repl :headless from the project directory in another shell. All non-lein grench invocations from inside the project directory will use that nREPL, but by setting the GRENCH_PORT environment variable you can connect to it from outside.

Leiningen

The grench lein subcommand is the exception to this; it connects to a Leiningen nREPL server rather than a project nREPL. It looks for the port in ~/.lein/repl-port or $LEIN_REPL_PORT; you can launch this server using lein repl :headless from outside a project directory.

Using Grenchman avoids waiting for Leiningen's JVM to start, but project JVMs are still launched like normal when necessary if Leiningen can't find a running project nREPL server. Note that this goes through Leiningen by looking for .nrepl-port and doesn't check $GRENCH_PORT.

Currently the Leiningen integration requires Leiningen 2.3.3 or newer. If you get no output from grench lein ... but your Leiningen process emits an java.io.FileNotFoundException: project.clj error message, upgrading Leiningen should fix it.

Building

Building grenchman typically requires compiling the whole OCaml toolchain (two compilers, two standard libraries, a package manager, and a handful of other third-party libraries) from scratch and can take up to an hour. Please use the precompiled binaries if possible.

You will need to install opam and OCaml 4.x to be able to build Grenchman. You'll also need libffi as well as libreadline-dev (sometimes called readline-devel on RPM systems).

If you're not sure whether you have 4.x installed or not, you can check with:

$ opam switch list
# If your system compiler is 4.x or above, you're ready to go.
# Otherwise, issue the following command:
$ opam switch 4.04.0
# Don't forget to add ~/.opam/4.04.0/bin/ to your $PATH

$ sudo apt install ocaml ocaml-native-compilers opam camlp4 aspcud \
    libreadline-dev libffi-dev

To build, run the following commands:

$ git clone git@github.com:technomancy/grenchman.git grenchman
$ cd grenchman
$ opam install ocamlfind core async ctypes ctypes-foreign
$ ocamlbuild -use-ocamlfind -lflags -cclib,-lreadline grench.native
$ ln -s $PWD/grench.native ~/bin/grench # or somewhere on your $PATH

Gotchas

By default Leiningen uses compilation settings which trade long-term performance for boot speed. With Grenchman you have long-running nREPL processes which start rarely, so you should disable this by putting :jvm-opts [] in your :user profile.

Tasks for all projects will share the same Leiningen instance, so projects with have conflicting plugins or hooks may behave unpredictably.