ClojureScript

Code allowed to re-define referred var

Details

  • Type: Defect Defect
  • Status: Open Open
  • Priority: Major Major
  • Resolution: Unresolved
  • Affects Version/s: 1.7.228
  • Fix Version/s: None
  • Component/s: None
  • Labels:
    None
  • Patch:
    Code and Test

Description

If you refer a var from another namespace, then you can def a new value for that var, and the def will mutate the other namespace, and other things will go wrong as illustrated in the example below.

FWIW, Clojure disallows this, and refuses to allow you to evaluate a def involving a referred var, and emits an error diagnostic like:

CompilerException java.lang.IllegalStateException: foo already refers to: #'some.name.space/foo in namespace: user, compiling:(NO_SOURCE_PATH:2:1)

Here is a complete example illustrating the issues:

Given:

(ns foo.core)

(defn square [x]
  (* x x))

then do this in a REPL:

cljs.user=> (require '[foo.core :refer [square]])
nil
cljs.user=> (var square)
#'foo.core/square
cljs.user=> (square 3)
9
cljs.user=> (ns-interns 'cljs.user)
{}
cljs.user=> (defn square [x] (+ x x))
WARNING: square already refers to: foo.core/square being replaced by: cljs.user/square at line 1 <cljs repl>
#'foo.core/square
cljs.user=> (square 3)
6
cljs.user=> (var square)
#'foo.core/square
cljs.user=> (in-ns 'foo.core)
nil
foo.core=> (square 3)
6
foo.core=> (in-ns 'cljs.user)
nil
cljs.user=> (ns-interns 'cljs.user)
{square #'cljs.user/square}
cljs.user=> (cljs.user/square 3)
TypeError: Cannot read property 'call' of undefined
    at repl:1:105
    at repl:9:3
    at repl:14:4
    at Object.exports.runInThisContext (vm.js:54:17)
    at Domain.<anonymous> ([stdin]:41:34)
    at Domain.run (domain.js:221:14)
    at Socket.<anonymous> ([stdin]:40:25)
    at emitOne (events.js:77:13)
    at Socket.emit (events.js:169:7)
    at readableAddChunk (_stream_readable.js:146:16)
cljs.user=> #'cljs.user/square
#'cljs.user/square
cljs.user=> @#'cljs.user/square
nil
  1. CLJS-1558.patch
    27/Nov/17 2:00 PM
    2 kB
    Mike Fikes
  2. CLJS-1558-2.patch
    02/Jul/18 12:14 PM
    2 kB
    Mike Fikes
  3. CLJS-1558-3.patch
    16/Jul/18 10:28 AM
    2 kB
    Mike Fikes

Activity

Hide
Mike Fikes added a comment -

The attached patch essentially turns the warning into an error for non-core names, throwing an exception that matches Clojure's.

Example:

$ script/noderepljs
ClojureScript Node.js REPL server listening on 49203
To quit, type: :cljs/quit
cljs.user=> (def map 3)
WARNING: map already refers to: cljs.core/map being replaced by: cljs.user/map at line 1 <cljs repl>
#'cljs.user/map
cljs.user=> (require '[clojure.set :refer [intersection]])
nil
cljs.user=> (def intersection 3)
clojure.lang.ExceptionInfo: intersection already refers to: #'clojure.set/intersection in namespace cljs.user at line 1 <cljs repl> {:file "<cljs repl>", :line 1, :column 1, :root-source-info {:source-type :fragment, :source-form (def intersection 3)}, :tag :cljs/analysis-error}
	at clojure.core$ex_info.invokeStatic(core.clj:4725)
	at clojure.core$ex_info.invoke(core.clj:4725)
	at cljs.analyzer$error.invokeStatic(analyzer.cljc:697)
...
Show
Mike Fikes added a comment - The attached patch essentially turns the warning into an error for non-core names, throwing an exception that matches Clojure's. Example:
$ script/noderepljs
ClojureScript Node.js REPL server listening on 49203
To quit, type: :cljs/quit
cljs.user=> (def map 3)
WARNING: map already refers to: cljs.core/map being replaced by: cljs.user/map at line 1 <cljs repl>
#'cljs.user/map
cljs.user=> (require '[clojure.set :refer [intersection]])
nil
cljs.user=> (def intersection 3)
clojure.lang.ExceptionInfo: intersection already refers to: #'clojure.set/intersection in namespace cljs.user at line 1 <cljs repl> {:file "<cljs repl>", :line 1, :column 1, :root-source-info {:source-type :fragment, :source-form (def intersection 3)}, :tag :cljs/analysis-error}
	at clojure.core$ex_info.invokeStatic(core.clj:4725)
	at clojure.core$ex_info.invoke(core.clj:4725)
	at cljs.analyzer$error.invokeStatic(analyzer.cljc:697)
...
Hide
Mike Fikes added a comment -

Here is an example showing that it is (as was before), OK to define a Var that shadows a core Var:

$ script/noderepljs
ClojureScript Node.js REPL server listening on 57077
To quit, type: :cljs/quit
cljs.user=> (defn quot [s] (str "'" s "'"))
WARNING: quot already refers to: cljs.core/quot being replaced by: cljs.user/quot at line 1 <cljs repl>
#'cljs.user/quot
cljs.user=> (quot "hello")
"'hello'"
cljs.user=> (cljs.core/quot 6 2)
3
Show
Mike Fikes added a comment - Here is an example showing that it is (as was before), OK to define a Var that shadows a core Var:
$ script/noderepljs
ClojureScript Node.js REPL server listening on 57077
To quit, type: :cljs/quit
cljs.user=> (defn quot [s] (str "'" s "'"))
WARNING: quot already refers to: cljs.core/quot being replaced by: cljs.user/quot at line 1 <cljs repl>
#'cljs.user/quot
cljs.user=> (quot "hello")
"'hello'"
cljs.user=> (cljs.core/quot 6 2)
3
Hide
Mike Fikes added a comment -

CLJS-1558-2.patch rebaselines

Show
Mike Fikes added a comment - CLJS-1558-2.patch rebaselines
Hide
Mike Fikes added a comment -

CLJS-1558-3.patch rebaselines

Show
Mike Fikes added a comment - CLJS-1558-3.patch rebaselines

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Dates

  • Created:
    Updated: