re-frame-trace

A trace panel for re-frame.

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, and provides several ways to visualise the structure and state of your re-frame application.

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 "0.1.0"]] }}
  

• 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

• 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.

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 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.

Development

Setting up re-frame-trace for development

You need both the re-frame-trace project and a test project to develop it against. For example, you can use the todo-mvc project.

• Clone re-frame-trace to your machine:

  git clone git@github.com:Day8/re-frame-trace.git
  

• Go into the root folder of the test project you're using to develop re-frame-trace with.

  cd /your/project/folder
  

• Add re-frame-trace into this test project using the instructions above.

• Still in the test project, create a folder called checkouts, then enter the folder:

  mkdir checkouts
  cd checkouts
  

• Create a relative symlink from your local re-frame-trace project in the checkouts folder. For example:

  ln -s ../relative/path/to/your/local/re-frame-trace re-frame-trace
  

• If you're using figwheel in the test project, you need to add the checkouts folder (checkouts/re-frame-trace/src) to :cljsbuild :source-paths in the project.clj file. If you're having trouble locating the right place to put this, it might help to look to a sample project.clj for inspiration. For example:

  :cljsbuild {:builds {:client {:source-paths ["checkouts/re-frame-trace/src"]}}}
  

• Now run your test project however you usually run it, and re-frame-trace should be in there. \o/

• Additionally, if modifying the .less CSS files, compile the css by running within the re-frame-trace directory:

  lein less auto
  

  to watch for changes, or one time by running:

  lein less once
  

  And then any time you want to reload the CSS, you have to manually save/touch styles.cljs. Figwheel will not do it for you. (See below for details).

Developing CSS

The styles for the trace panel are defined both inline and in a LESS file. To develop the styles, edit resources/day8/re_frame/trace/main.less and run

lein less auto

to watch the LESS file and automatically recompile on changes.

Don't edit the CSS file resources/day8/re_frame/trace/main.css directly, as it will be overwritten.

We are using CSS preprocessing because in order to isolate the panel styles, we are namespacing the panel styles with the id #--re-frame-trace--.

Problems while developing CSS

• You must touch or save the styles.cljs file to trigger a CSS reload if you're editing main.less. This is because styles.cljs slurps main.css with a macro that happens before Clojurescript compilation, so figwheel isn't aware of the changes.
• Did you run lein less auto or lein less once to compile LESS to CSS?
• Try clearing your browser cache/hard-reloading.