Clojure: The Bad Parts

Slide deck from my talk at Partial Conf 2017.

Transcript

2. Божидар
3. Bozhidar
4. Bozho cool
5. Bozo not cool
6. Божo
7. Bug cool
10. I’m an Emacs fanatic
13. bbatsov
14. Ruby & Rails style guides
18. Clojure Style Guide
19. Clojure: THE BAD PARTS by Bozhidar Batsov
20. Disclaimer
21. I love Clojure
22. I have a huge respect for Clojure’s team
23. Complaining is much easier than running a major project
24. Stewardship: The Sobering Parts https://www.youtube.com/watch?v=2y5Pv4yN0b0 must see
25. Clojure is still way better than JavaScript
28. Technical problems
29. ((((((()))))))
31. Bloated clojure.core
32. char-escape-string
33. char-name-string
34. subs
35. clojure.string
36. fi le-seq & line-seq
37. clojure.java.io
38. xml-seq
39. char-array, double-array, etc
40. unchecked-*
41. bit-*
42. re-*
43. Odd API decisions
44. defn-
45. Where are def- and defmacro-?
46. (some even? '(1 2 3 4))
47. (some? even? '(1 2 3 4))
48. (not-any? even? '(1 2 3 4))
49. Tight coupling with Java
50. Most Clojure libs/tools depend directly on Java
51. clojure.java.io
52. clojure.io
53. ClojureCLR is basically abandonware
54. Hard to write portable code
55. #?(:clj (Clojure expression) :cljs (ClojureScript expression) :cljr (Clojure CLR expression) :default (fallthrough expression))
56. Clojure’s internals are outdated
57. Clojure’s older internals were never updated to use protocols
58. Obscure stacktraces
59. Exception in thread "main" java.lang.RuntimeException: Unable to resolve symbol: i-dont-exist in this context, compiling:(one_man_wiki/views.clj:18) at clojure.lang.Compiler.analyze(Compiler.java:6281) at clojure.lang.Compiler.analyze(Compiler.java:6223) at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618) at clojure.lang.Compiler$FnMethod.parse(Compiler.java:5054) at clojure.lang.Compiler$FnExpr.parse(Compiler.java:3674) at clojure.lang.Compiler.analyzeSeq(Compiler.java:6453) at clojure.lang.Compiler.analyze(Compiler.java:6262) at clojure.lang.Compiler.analyzeSeq(Compiler.java:6443) at clojure.lang.Compiler.analyze(Compiler.java:6262) at clojure.lang.Compiler.access$100(Compiler.java:37) at clojure.lang.Compiler$DefExpr$Parser.parse(Compiler.java:518) at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455) at clojure.lang.Compiler.analyze(Compiler.java:6262) at clojure.lang.Compiler.analyze(Compiler.java:6223) at clojure.lang.Compiler.eval(Compiler.java:6515) at clojure.lang.Compiler.load(Compiler.java:6952) at clojure.lang.RT.loadResourceScript(RT.java:359) at clojure.lang.RT.loadResourceScript(RT.java:350) at clojure.lang.RT.load(RT.java:429) at clojure.lang.RT.load(RT.java:400) at clojure.core$load$fn__4890.invoke(core.clj:5415) at clojure.core$load.doInvoke(core.clj:5414) at clojure.lang.RestFn.invoke(RestFn.java:408) at clojure.core$load_one.invoke(core.clj:5227) at clojure.core$load_lib.doInvoke(core.clj:5264) at clojure.lang.RestFn.applyTo(RestFn.java:142) at clojure.core$apply.invoke(core.clj:603) at clojure.core$load_libs.doInvoke(core.clj:5298) at clojure.lang.RestFn.applyTo(RestFn.java:137) at clojure.core$apply.invoke(core.clj:603) at clojure.core$require.doInvoke(core.clj:5381) at clojure.lang.RestFn.invoke(RestFn.java:457) at one_man_wiki.handler$eval1564$loading__4784__auto____1565.invoke(handler.clj:1) at one_man_wiki.handler$eval1564.invoke(handler.clj:1) at clojure.lang.Compiler.eval(Compiler.java:6511) at clojure.lang.Compiler.eval(Compiler.java:6501) at clojure.lang.Compiler.load(Compiler.java:6952) at clojure.lang.RT.loadResourceScript(RT.java:359) at clojure.lang.RT.loadResourceScript(RT.java:350) at clojure.lang.RT.load(RT.java:429) at clojure.lang.RT.load(RT.java:400) at clojure.core$load$fn__4890.invoke(core.clj:5415) at clojure.core$load.doInvoke(core.clj:5414) at clojure.lang.RestFn.invoke(RestFn.java:408) at clojure.core$load_one.invoke(core.clj:5227) at clojure.core$load_lib.doInvoke(core.clj:5264) at clojure.lang.RestFn.applyTo(RestFn.java:142) at clojure.core$apply.invoke(core.clj:603) at clojure.core$load_libs.doInvoke(core.clj:5298) at clojure.lang.RestFn.applyTo(RestFn.java:137) at clojure.core$apply.invoke(core.clj:603) at clojure.core$require.doInvoke(core.clj:5381) at clojure.lang.RestFn.invoke(RestFn.java:421) at user$eval1.invoke(NO_SOURCE_FILE:1) at clojure.lang.Compiler.eval(Compiler.java:6511) at clojure.lang.Compiler.eval(Compiler.java:6500) at clojure.lang.Compiler.eval(Compiler.java:6477) at clojure.core$eval.invoke(core.clj:2797) at clojure.main$eval_opt.invoke(main.clj:297) at clojure.main$initialize.invoke(main.clj:316) at clojure.main$null_opt.invoke(main.clj:349) at clojure.main$main.doInvoke(main.clj:427) at clojure.lang.RestFn.invoke(RestFn.java:421) at clojure.lang.Var.invoke(Var.java:419) at clojure.lang.AFn.applyToHelper(AFn.java:163) at clojure.lang.Var.applyTo(Var.java:532) at clojure.main.main(main.java:37) Caused by: java.lang.RuntimeException: Unable to resolve symbol: i-dont-exist in this context at clojure.lang.Util.runtimeException(Util.java:170) at clojure.lang.Compiler.resolveIn(Compiler.java:6766) at clojure.lang.Compiler.resolve(Compiler.java:6710) at clojure.lang.Compiler.analyzeSymbol(Compiler.java:6671) at clojure.lang.Compiler.analyze(Compiler.java:6244) ... 66 more
60. (defn no-such-variable [] i-dont-exist)
61. API docs
62. Does Clojure provide us the infrastructure to create awesome API documentation?
63. No.
65. The docstring format is bad
66. •no clear formatting rules •it’s not editor-friendly •it’s hard to make out parameters and references there
67. (defn str "With no args, returns the empty string. With one arg x, returns x.toString(). (str nil) returns the empty string. With more than one arg, returns the concatenation of the str values of the args." {:tag String :added "1.0" :static true} (^String [] "") (^String [^Object x] (if (nil? x) "" (. x (toString)))) (^String [x & ys] ((fn [^StringBuilder sb more] (if more (recur (. sb (append (str (first more)))) (next more)) (str sb))) (new StringBuilder (str x)) ys)))
68. (defn str "With no args, returns the empty string. With one arg x, returns x.toString(). (str nil) returns the empty string. With more than one arg, returns the concatenation of the str values of the args." {:tag String :added "1.0" :static true}
69. Comparison with Emacs Lisp
70. (defun cider-interactive-eval (form &optional callback bounds additional-params) "Evaluate FORM and dispatch the response to CALLBACK. If the code to be evaluated comes from a buffer, it is preferred to use a nil FORM, and specify the code via the BOUNDS argument instead. This function is the main entry point in CIDER's interactive evaluation API. Most other interactive eval functions should rely on this function. If CALLBACK is nil use `cider-interactive-eval-handler'. BOUNDS, if non-nil, is a list of two numbers marking the start and end positions of FORM in its buffer. ADDITIONAL-PARAMS is a plist to be appended to the request message. If `cider-interactive-eval-override' is a function, call it with the same arguments and only proceed with evaluation if it returns nil."
71. (defn str "Converts something to a string. With no args, returns the empty string. With one arg X, returns `x.toString()`. `(str nil)` returns the empty string. With more than one arg, returns the concatenation of the string values of the args." {:tag String :added "1.0" :static true}
72. Namespace documentation
73. (ns ^{:doc "edn reading." :author "Rich Hickey"} clojure.edn (:refer-clojure :exclude [read read-string]))
74. (ns ^{:author "Stuart Sierra, Stuart Halloway, David Liebke"} "Clojure String utilities It is poor form to (:use clojure.string). Instead, use require with :as to specify a prefix, e.g. (ns your.namespace.here (:require [clojure.string :as str])) Design notes for clojure.string: 1. Strings are objects (as opposed to sequences). As such, the string being manipulated is the first argument to a function; passing nil will result in a NullPointerException unless documented otherwise. If you want sequence-y behavior instead, use a sequence. 2. Functions are generally not lazy, and call straight to host methods where those are available and efficient. 3. Functions take advantage of String implementation details to write high-performing loop/recurs instead of using higher-order functions. (This is not idiomatic in general-purpose application code.) 4. When a function is documented to accept a string argument, it will take any implementation of the correct *interface* on the host platform. In Java, this is CharSequence, which is more general than String. In ordinary usage you will almost always pass concrete strings. If you are doing something unusual, e.g. passing a mutable implementation of CharSequence, then thread-safety is your responsibility." clojure.string (:refer-clojure :exclude (replace reverse)) (:import (java.util.regex Pattern Matcher) clojure.lang.LazilyPersistentVector))
75. Some def macros don’t support docstrings directly
76. (defonce ^:dynamic ^{:private true :doc "A ref to a sorted set of symbols representing loaded libs"} *loaded-libs* (ref (sorted-set)))
77. This shouldn’t be hard to fi x, right?
78. No uni fi ed convention about documentation-related metadata usage
79. How do you handle deprecations?
80. How do you indicate when something was introduced/ changed?
81. (defn agent-errors "DEPRECATED: Use 'agent-error' instead. Returns a sequence of the exceptions thrown during asynchronous actions of the agent." {:added "1.0" :deprecated "1.2"} [a] (when-let [e (agent-error a)] (list e))) (defn clear-agent-errors "DEPRECATED: Use 'restart-agent' instead. Clears any exceptions thrown during asynchronous actions of the agent, allowing subsequent actions to occur." {:added "1.0" :deprecated "1.2"} [^clojure.lang.Agent a] (restart-agent a (.deref a)))
82. How do you indicate how some macro is supposed to be indented by Clojure editors?
83. What’s the metadata every function should have?
84. And what about each namespace?
85. Common Metadata • version added (e.g. “:added”) • version compatibility broken (e.g. “:changed”) • version when deprecated (e.g. “:deprecated”) • superseded by • related symbols (e.g. “:see also”) • indentation speci fi cation
86. Specifying indentation
87. (defmacro with-in-str "[DOCSTRING]" {:style/indent 1} [s & body] (bla bla bla))
88. (with-in-str some-str (something) (quick))
89. (with-in-str some-str (something) (quick))
90. (defmacro do "[DOCSTRING]" {:style/indent 0} [& body] (bla bla bla))
91. (do (something) (quick))
92. http://cider.readthedocs.io/ en/latest/indent_spec/
93. Stewardship
94. Contributing is hard
95. A lot of decisions are made behind closed doors
96. Unpredictable release schedule
97. (Almost) No bug fi x releases
98. clojure-contrib
99. Projects in permanent alpha state
100. No projects ever get promoted to Clojure itself
101. Most contrib projects have between 0 and 1 maintainers
103. Contrib is a failed experiment that has to be shutdown
104. Documentation???
105. clojure.org
109. clojuredocs.org
110. clojure-doc.org
111. conj.io
113. Something’s de fi nitely wrong with Clojure’s documentation…
114. The Problems
115. Clojure’s core team doesn’t care much about documentation
116. It’s hard to contribute simple documentation fi xes
117. Relax the rules for documentation improvements
118. •don’t require CA for doc improvements •accept doc improvements via GitHub •have a simpli fi ed review process for doc improvements
119. clojure.org already does this!!!
120. (but I guess many people don’t know that)
121. Clojure itself doesn’t
122. Epilogue
123. –Mahatma Gandhi “You must be the change you wish to see in the world.”
124. –Bozhidar Batsov “You must be the change you wish to see in the code.”
125. Dunaj (http://www.dunaj.org)
126. Jaunt (https://github.com/jaunt-lang/jaunt)
127. File tickets
128. Send patches
129. Blog about the issues
130. Speak about the issues
131. Let’s make Clojure awesome together!
132. Let’s make Clojure better together!
133. Let’s make Clojure more awesome together!
134. Clojure Clojure
135. Felina
136. Epilogue twitter: @bbatsov github: @bbatsov http//batsov.com http://emacsredux.com Partical Conf So fi a, Bulgaria 22.09.2017