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re-frame-trace

re-frame-trace is a programmer's dashboard for inspecting, understanding and debugging a running re-frame application.

Status: Alpha.

Note the latest version 0.1.13 ALSO requires the latest version of re-frame itself - v0.10.3-alpha1.

Dashboard Overview

re-frame applications have a very regular computational path: first an event happens, and then boom, boom, boom go a series of known dominos, in a known order. At the end of it, a re-frame app lapses into a quiescent state waiting for the next event to kick off the next iteration of the cycle.

We use the term dashboard for this tool quite deliberately. In the business world, dashboards are used to show rolled up and summarised data along useful dimensions. The detailed data in not shown unless it interests you and you wish to drill down into it.

As it runs, re-frame generates detailed "trace data", but a lot of it will be low level and uninteresting, much of the time. So, as a "dashboard", re-frame-trace shows useful, "rolled up" information "at a glance", while also allowing you to drill down and explore the detail as necessary. All the data you want should be available, but you shouldn't drown in it.

Each re-frame event and its consequent computation forms a logically discrete "epoch" which can be analysed and inspected independently of other epochs. As a result, the dashboard design is epoch-oriented.

Not only is the underlying trace "just data", but so is much of the observed re-frame proecess. Much of what re-frame does on your behalf is the move data from one domino to another. You write the dominos (functions) and re-frame will flow data through them.

So, yeah, its an epoch-oriented, interactive data dashboard for gaining insights and assisting debugging. It is also a work in progress, so this descrption runs well ahead of what is delivered now.

More Aspirational goals

Here's the vision for what we'd like re-frame-trace to deliver (eventually):

Help in learning re-frame. If I'm new to re-frame, the dashboard should assist me to understand the dominoes and the data flows involved.
Help in learning a new code base. It should help me to explore how an unfamiliar application is wired together. When I click on this button "X", it shows me what event is dispatch-ed and in what namespace the associated event handler is registered. And, "oh look, that's interesting - four subscriptions recalculated". Etc.
Debugging assistance. Particularly assistance for writing event handlers as they hold most of the application logic.
A method for finding performance problems and/or detecting where there is unnecessary computation.

Visual Sampler

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.

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

: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:

{: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 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 is instrumented - all important activity generates trace data. re-frame-trace consumes this trace data and renders useful visualisations of the re-frame process. Currently, re-frame's tracing capabilities are in alpha and are subject to change at any time. We're testing the utility of the the trace by building an app on top.

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 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.

Citations

open by Bluetip Design from the Noun Project
reload by Adnen Kadri from the Noun Project
Camera by Christian Shannon from the Noun Project

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