The Evolution of the Clojure Tooling for Emacs

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The Evolution of the Clojure tooling for Emacs narrated by Bozhidar I. Batsov

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Hello!

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@bbatsov

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Bug

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A (Dark) Knight of the Order of Emacs

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Why I am here?

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Bulgaria

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2013 Other 24% LightTable 8% CCW 8% ﬁreplace 10% Cursive 3% CIDER 48% 2014 Other 13% LightTable 12% CCW 5% ﬁreplace 14% Cursive 14% CIDER 42%

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–Nancy Pearcey “Competition is always a good thing. It forces us to do our best. A monopoly renders people complacent and satisﬁed with mediocrity.”

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The critics

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CIDER sucks big time!

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CIDER breaks on every update!

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CIDER has become bloated and slow!

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CIDER’s setup is overly complex!

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CIDER is doing great!

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Near future Others 10% CIDER 90%

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Near future Cursive 25% Others 15% CIDER 60%

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A not so long time ago in a galaxy not far away…

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Java, PHP and .NET ruled the dev world

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Lisps were out of fashion

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2007

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A gentleman & a scholar

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Clojure

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Biggest Clojure problem at launch?

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0 Clojure dev environments

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Emacs was the last Lisp stronghold

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SLIME

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Superior Lisp Interaction Mode for Emacs

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SLIME Features • REPL • Interactive evaluation • Compilation notes • Code completion • Deﬁnition lookup • Documentation lookup • Apropos

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SLIME Features • Debugger • Value inspector • Tracing • Find usages • Macroexpansion • Scratchpad • Minibuffer code evaluation

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SLIME (Emacs Lisp) SWANK (Common Lisp) Clozure RPC LispWorks CMUCL ABCL SBCL Client Server Backends

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2008

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clojure-mode & swank-clojure

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SLIME (Emacs Lisp) SWANK (Common Lisp) swank-clojure

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A star was born

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swank-clojure • Requires knowledge of swank (Common Lisp) • Bundles a frozen SLIME version • Subpar features (e.g. debugger, inspector, ﬁnd usages) • Monolithic (no swank plugins)

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SLIME is a Common Lisp tool

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2010

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Another esteemed gentleman & scholar

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nREPL

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A common foundation for Clojure dev tools

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• Load (compile) a Clojure ﬁle • Evaluate a Clojure form • Interrupt evaluation • Read from the standard input

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Extensible via middleware

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2012

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nrepl.el

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nrepl.el (Emacs Lisp) nREPL (Clojure)

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A workhorse is retired

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nrepl.el • lacked many SLIME features • relied heavily on evaluation of inlined code • made assumptions about the environment • ﬂawed bencode parser

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2013

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Don’t settle for good. Demand great!

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–Phil Karlton “There are only two hard things in Computer Science: cache invalidation and naming things.”

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Clojure Integrated Development Environment & REPL

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Clojure Interactive Development Environment Reimagined

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CIDER (Emacs Lisp) nREPL (Clojure) cider-nrepl

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(defun nrepl-jump-to-def (var) "Jump to the definition of the VAR at point." (let ((form (format "(let [ns-symbol '%s ns-var '%s ns-file (clojure.core/comp :file clojure.core/meta clojure.core/second clojure.core/first clojure.core/ns-publics) resource-str (clojure.core/comp clojure.core/str clojure.java.io/resource ns-file) file-str (clojure.core/comp clojure.core/str clojure.java.io/file ns-file)] (cond ((clojure.core/ns-aliases ns-symbol) ns-var) (let [resolved-ns ((clojure.core/ns-aliases ns-symbol) ns-var)] [(resource-str resolved-ns) (file-str resolved-ns) 1]) (find-ns ns-var) [(resource-str ns-var) (file-str ns-var) 1] (clojure.core/ns-resolve ns-symbol ns-var) ((clojure.core/juxt (clojure.core/comp clojure.core/str clojure.java.io/resource :file) (clojure.core/comp clojure.core/str clojure.java.io/file :file) :line) (clojure.core/meta (clojure.core/ns-resolve ns-symbol ns-var)))))" (nrepl-current-ns) var))) (nrepl-send-string form (nrepl-jump-to-def-handler (current-buffer)) nrepl-buffer-ns (nrepl-current-tooling-session)))) not portable

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(defun cider-jump-to-var (&optional var line) "Jump to the definition of VAR, optionally at a specific LINE. When called interactively, this operates on point, or falls back to a prompt." (interactive) (cider-ensure-op-supported "info") (cider-read-symbol-name "Symbol: " (lambda (var) (-if-let (info (cider-var-info var)) (cider--jump-to-loc-from-info info) (message "Symbol %s not resolved" var))))) portable

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CIDER Features • Interactive evaluation • Compilation notes • Code completion • Deﬁnition lookup • Documentation lookup • Apropos

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CIDER Features • Value inspector • Command selector • Tracing • Macroexpansion • Scratchpad • Minibuffer code evalution

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Bonus features

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Javadoc support

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JavaDoc Support

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C-c C-d d

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Jump to Java deﬁnition

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JavaDoc Support

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M-.

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Jump to resource

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C-c M-.

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resources/conj/demo/resource.txt

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Sanity-preserving stacktraces

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clojure.test integration

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C-c ,

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Namespace Browser

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Classpath browser

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Grimoire integration

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C-c C-d g

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• nREPL session manager • Smart ns reloading • ClojureScript support

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Extensions (are easy)

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• refactoring (clj-refactor + refactor-nrepl) • proﬁling (cider-proﬁle + nrepl-refactor) • session tracking (cider-spy + cider-spy-nrepl)

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CIDER tastes better than SLIME

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What’s still missing?

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• Debugger • Find usages • A proper manual CIDER 1.0

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Why CIDER?

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IDE

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Emacs

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Emacs users know how to build productive Lisp workﬂows

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• Emacs (ultimate Elisp dev env) • SLIME (and SLY) • Geiser • racket-mode • CIDER (obviously)

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• paredit • smartparens • rainbow-delimiters • rainbow-identiﬁers • sexp-fu • paxedit