Cognitect REBL data browser

Cognitect REBL captures the results of evaluating expressions and visualizes them in a human readable form. REBL was initially created to support development with the Datomic database and is useful viewing and navigating data structures, especially nested data structures and large data sets.

REBL requires an end user license and a personal access token to obtain the packaged library.

Open alternatives include Reveal and Portal, which are simpler to install.

Sign-up for Cognitect dev-tools license

REBL is part of the Cognitect dev-tools project that also includes Datomic dev-local (local running instance of Datomic).

Accept the Cognitect dev-tools license to receive an email containing a link to download the latest version of Datomic local and a personal access token for access to the Cognitect Maven repository which contains the REBL library.

Follow the maven configuration link in the email to configure your build tool (Clojure CLI tools or Leiningen) and the repository in the project pom.xml.

Aliases for Cognitect REBL

Follow the REBL installation steps to create an alias in the user-wide deps.edn configuration.

Alternatively, use the practicalli/clojure-deps-edn configuration which contains the :inspect/rebl alias for use with Java 11.

Running REBL with a project

Run the project using the Clojure CLI tools

clojure -M:inspect/rebl

If rlwrap is installed, then use:

clj -M:inspect/rebl

Configure REBL with Clojure editors

nrebl.middleware is a middleware library that listens to the nREPL connection between editor and REPL, sending the results of every evaluation to Cognitect REBL.

Cognitect REBL with CIDER in Spacemacs

This library is described as very alpha but works in basic tests run by Practicalli.

An :middleware/nrebl alias along with the supporting :lib/cider-nrepl aliases are included in practicalli/clojure-deps-edn configuration

Add an alias called :middleware/nrebl to ~/.clojure/deps.edn or a deps.edn file in the root of a specific project

:middleware/nrebl
  {:extra-deps {rickmoynihan/nrebl.middleware {:mvn/version "0.3.1"}}
   :main-opts  ["-e" "((requiring-resolve,'cognitect.rebl/ui))"
                "-m" "nrepl.cmdline"
                "-i"
                "--middleware" "[nrebl.middleware/wrap-nrebl,cider.nrepl/cider-middleware]"]}

Supporting aliases for nrebl.middleware

:lib/cider-nrepl
  {:extra-deps {nrepl/nrepl                   {:mvn/version "0.8.2"}
                cider/cider-nrepl             {:mvn/version "0.25.3"}
                refactor-nrepl/refactor-nrepl {:mvn/version "2.5.0"}}}

Using REBL with Clojure editors

CIDER and Calva use the nREPL protocol to connect to the REBL REPL and have all the evaluated code in those editors automatically display the results in the REBL UI.

In a terminal, run REBL listening to nREPL using the command

clojure -M:lib/cider-nrepl:inspect/rebl:middleware/nrebl

Then cider-connect-clj in Spacemacs / Emacs and CIDER will connect to the nREPL port and results of evaluated code are sent to REBL UI.

Using cider-jack-in - not recommended

To use cider-jack-in-clj add a .dir-locals.el file to the root of a Clojure project. The .dir-locals.el configuration adds the nREBL aliases set via cider-clojure-cli-global-options. The automatically injected configuration must be disabled or the command will fail.

((clojure-mode . ((cider-preferred-build-tool . clojure-cli)
                  (cider-clojure-cli-global-options . "-M:lib/cider-nrepl:inspect/rebl:middleware/nrebl")
                  (cider-jack-in-dependencies . nil)
                  (cider-jack-in-nrepl-middlewares . nil)
                  (cider-jack-in-lein-plugins . nil)
                  (cider-clojure-cli-parameters . ""))))

revert-buffer will force Emacs to load in the .dir-locals.el configuration if it was added to a project with files already opened.

See the guide on using VSCode Calva with REBL

References

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