# clj-stacktrace

A library for creating more readable stacktraces in Clojure programs.

For example, to print a nice stack trace in a REPL:

    => (use 'clj-stacktrace.repl)
    => ("foo")
    java.lang.ClassCastException: java.lang.String cannot be cast to clojure.lang.IFn (NO_SOURCE_FILE:0)
           Compiler.java:5440 clojure.lang.Compiler.eval
           Compiler.java:5391 clojure.lang.Compiler.eval
                core.clj:2382 clojure.core/eval
                 main.clj:183 clojure.main/repl[fn]
                 main.clj:204 clojure.main/repl[fn]
                 main.clj:204 clojure.main/repl
              RestFn.java:422 clojure.lang.RestFn.invoke
                 main.clj:262 clojure.main/repl-opt
                 main.clj:355 clojure.main/main
              RestFn.java:398 clojure.lang.RestFn.invoke
                 Var.java:361 clojure.lang.Var.invoke
                 AFn.java:159 clojure.lang.AFn.applyToHelper
                 Var.java:482 clojure.lang.Var.applyTo
                 main.java:37 clojure.main.main
    Caused by: java.lang.String cannot be cast to clojure.lang.IFn
             NO_SOURCE_FILE:2 user/eval100
           Compiler.java:5424 clojure.lang.Compiler.eval

In stack traces printed by `pst`:

- Java methods are described with the usual `name.space.ClassName.methodName` convention and Clojure functions with their own `name.space/function-name` convention.
- Anonymous clojure functions are denoted by adding an `[fn]` to their enclosing, named function.
- "Caused by" cascades are shown as in regular java stack traces.
- Elements are vertically aligned for better readability.
- Printing is directed to `*out*`.

If you want to direct the printing to somewhere other than `*out*`, either use `pst-on` to specify the output location or `pst-str` to capture the printing as a string.

The library also offers an API for programatically 'parsing' exceptions. This API is used internal for `pst` and can be used to e.g. improve development tools. Try for example:

`clj (use 'clj-stacktrace.core) (try ("nofn") (catch Exception e (parse-exception e)))`

## Leiningen

If you use Leiningen, you can install clj-stacktrace on a user-wide basis. Just add the following to `~/.lein/profiles.clj`:

`clj {:user {:dependencies [[clj-stacktrace "0.2.7"]] :injections [(let [orig (ns-resolve (doto 'clojure.stacktrace require) 'print-cause-trace) new (ns-resolve (doto 'clj-stacktrace.repl require) 'pst)] (alter-var-root orig (constantly @new)))]}}`

The `:injections` clause replaces the built-in stack trace printing with enhanced clj-stacktrace version; you can leave it out if you plan on invoking clj-stacktrace functions directly or are using tools which are already clj-stacktrace-aware.

## License

Copyright © 2009-2013 Mark McGranaghan and contributors.

Released under an MIT license.