Debuggers

nREPL

https://github.com/clojure/tools.nrepl

• transport (socket & bencode)

• middleware stack

Driven by Chas Emerick / @cemerick

load-file

Support for Clojure and ClojureScript

Leiningen Profiles

Configure your favourite middleware in ~/.lein/profiles.clj.

:user
  {:repl-options
    {:nrepl-middleware
     [ritz.nrepl.middleware.doc/wrap-doc]}}

Or add project specific middleware in project.clj

:dev
  {:repl-options
    {:nrepl-middleware
     [ritz.nrepl.middleware.doc/wrap-doc]}}

reply

Colin Jones @trptcolin https://github.com/trptcolin/reply

CounterClockWise

Laurent Petit @petitlaurent http://code.google.com/p/counterclockwise.

VimClojure

Meikel Brandmeyer @kotarak VimClojure.

and …

nrepl.el

https://github.com/kingtim/nrepl.el

An Emacs client for the nREPL protocol, unfettered by support of any other lisp.

Driven by Tim King

Install nrepl.el

nrepl.el is available as an Emacs package in Marmalade.

(require 'package)
(add-to-list 'package-archives
 '("marmalade"
   . "http://marmalade-repo.org/packages/"))
(package-initialize)

The git HEAD is packaged to MELPA.

(add-to-list 'package-archives
 '("melpa"
   . "http://melpa.milkbox.net/packages/"))

Install nrepl.el ...

In either case, to actually install nrepl:

M-x package-install nrepl

Running nrepl.el

Browse to a file in your clojure project an jack-in:

M-x nrepl-jack-in

Running nrepl.el ...

Start an nREPL server, possibly with lein.

lein repl :headless

Connect to the nREPL server. lein announces the port the REPL is running on.

M-x nrepl localhost 41045

Ritz

https://github.com/pallet/ritz

Started life as a fork of swank-clojure, but is now a very different codebase.

Initially was to provide SLDB for Clojure in SLIME.

Now refactored to support nREPL.

Ritz Components

Ritz nREPL Middleware

Can be used in any nREPL server

javadoc

javadoc for symbol

apropos

doc for related functions

doc

Clojure doc for symbol

describe-symbol

Clojure doc and description

complete

simple and fuzzy completion

eval

keep track of source forms

More Ritz Components

nrepl-codeq

Middleware for function history via codeq

nrepl-hornetq

An nREPL server over HornetQ

Ritz Debugger

Refactored after reading Out of the Tar Pit, Ben Moseley, Peter Marks 2006.

• Isolate mutable state
• Provide simple data query and update ops
• No preferred access path

Map for each connection, with assoc and update-in functions for different areas within the connection.

Ritz Debugger Middleware

Could be used by other (non-emacs) clients.

Emacs package for nrepl.el extensions.

Ritz Debugger

Using Ritz nREPL Debugger

Install

Install the nrepl-ritz.el Emacs package:

M-x package-install nrepl-ritz

Add lein-ritz to you :plugins in ~/.lein/profiles.clj

:user {:plugins [[lein-ritz "0.6.0"]]

Using Ritz nREPL Debugger

Run

Run the ritz nREPL server:

lein ritz-nrepl

Connect to the repl server, specifying the port:

M-x nrepl 4005

Break on exception

Examine stack traces before the stack unwinds. Needs to be turned on:

M-x nrepl-ritz-break-on-exception

user> (/ 1 0)

Break on exception - restarts

Filtering of exceptions is via "restarts" displayed as part of the stacktrace.

Divide by zero
java.lang.ArithmeticException

Restarts:
 0: [CONTINUE] Pass exception to program
 1: [ABORT] Abort request.
 2: [IGNORE] Do not enter debugger for this exception type
 3: [IGNORE-MSG] Do not enter debugger for this exception message
 4: [IGNORE-CATCH] Do not enter debugger for exceptions with
    catch location clojure.lang.Compiler.*
 5: [IGNORE-LOC] Do not enter debugger for exceptions with throw
    location clojure.lang.Numbers.*

Stacktrace:
  0: clojure.lang.Numbers.divide (Numbers.java:156)
  1: clojure.lang.Numbers.divide (Numbers.java:3691)
  2: ritz-conj.example/eval2845 (UNKNOWN:-1)

What's caught, and what's not

Any (try ... (finally ..)) block means that JPDA considers an exception within that block as caught

(with-open [f (io/reader f)] ...)

Makes filtering on caught/uncaught meaningless.

Evaluation

You can evaluate an expression within the context of a frame. Just select the frame, and press:

• 'e' and enter an expression to see the result in the message area.
• 'd' and enter an expression to see a pretty printed result in a separate buffer.

Inspector

In ritz-swank, just press Enter on any local variable to pop up the SLIME inspector.

Locals Clearing

Clojure does something called locals clearing, to avoid holding onto the head of lazy sequences. This can result in locals showing up as nil, even when they aren't really.

Can be switched off in 1.4+

Locals Clearing - Disable on Compile

Use a prefix argument (C-u)to the following commands to disable locals clearing on the code being compiled.

Locals Clearing - Disable Globally

To disable locals clearing globally:

(alter-var-root #'*compiler-options*
  assoc :disable-locals-clearing true)

Breakpoints

SLIME only for now

Press C-c C-x C-b to set a breakpoint on any line (of clojure or java).

Restarts for Step, Step Over, and Step Out

Direction - Other possibilities

Scriptable debugging

http://www.cs.brown.edu/~sk/Publications/Papers/Published/mcskr-dataflow-lang-script-debug-journal/