# re-frame-trace

A trace panel for re-frame.

[![Clojars Project](https://img.shields.io/clojars/v/day8.re-frame/trace.svg)](https://clojars.org/day8.re-frame/trace)

**Status:** Alpha.

## Motivation

re-frame provides a data driven architecture, but we need to be able to inspect it. re-frame-trace takes inspiration from [redux-devtools](https://github.com/gaearon/redux-devtools), and provides several ways to visualise the structure and state of your re-frame application.

<img src="docs/images/trace-window.gif" height="400px">

## Installation

If you are using leiningen, modify `project.clj` in the following ways. When puzzling over the various possible leiningen configurations, it's often helpful to look at a sample [project.clj](https://github.com/technomancy/leiningen/blob/stable/sample.project.clj).

[![Clojars Project](https://img.shields.io/clojars/v/day8.re-frame/trace.svg)](https://clojars.org/day8.re-frame/trace)

- Add re-frame-trace as a dev dependency by placing `[day8.re-frame/trace "VERSION"]` within `:profiles :dev :dependencies`. For example:

  ```cljs
  :profiles
     {:dev
        {:dependencies [[some-other-package  "0.0.0"]
                        [day8.re-frame/trace "0.0.0 (see version above)"]] }}
  ```

- Locate the `:compiler` map under `:dev` and add:

  - `:closure-defines      {"re_frame.trace.trace_enabled_QMARK_" true}`
  - `:preloads             [day8.re-frame.trace.preload]`

  For example:

  ```cljs
  {:builds
     [{:id           "dev"
       :source-paths ["src" "dev"]
       :compiler     {...
                      :closure-defines      {"re_frame.trace.trace_enabled_QMARK_" true}
                      :preloads             [day8.re-frame.trace.preload]}}]}
  ```

[cljs-devtools](https://github.com/binaryage/cljs-devtools) is not required to use re-frame-trace, but it is highly recommended.

## Usage

- **Make sure you have followed all of the installation instructions above.**

- Start up your application.

- Once it is loaded, focus the document window and press `ctrl-h` to slide open the trace panel and enable tracing.

- When the panel is closed, tracing is disabled.

## Troubleshooting

* Try a `lein clean`
* Make sure you have followed all the installation steps.

## How does it work?

re-frame has instrumentation to collect traces throughout various important points in the lifecycle of a re-frame app. re-frame-trace is a consumer of these traces, and provides visualisations of the traces. These traces have a well-defined structure, and will eventually be standardised, allowing other developers to create their own tooling to work against the traces. Currently, re-frame's tracing and re-frame-trace are in alpha and are subject to change at any time.

By default, re-frame tracing is compiled out, so it won't impose a performance cost in production. The trade-off here is that you need to explicitly enable it in development.

The [preloads](https://github.com/clojure/clojurescript/wiki/Compiler-Options#preloads) option (`:preloads [day8.re-frame.trace.preload]`) has to be set in order to automatically monkeypatch Reagent to add appropriate lifecycle hooks. Yes this is gross, and yes we will try and make a PR to reagent to add proper hooks, once we know exactly what we need. The preload namespace also injects a div containing the devtools panel into the DOM.

## Developing/Contributing

If you want to work on re-frame-trace, see [DEVELOPERS.md](DEVELOPERS.md).

## Citations

[open](https://thenounproject.com/search/?q=popout&i=334227) by Bluetip Design from the Noun Project