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[CLJ-1210] error message for (clojure.java.io/reader nil) — consistency for use with io/resource Created: 23/May/13  Updated: 12/Jul/14

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: Release 1.5
Fix Version/s: None

Type: Enhancement Priority: Minor
Reporter: Trevor Wennblom Assignee: Unassigned
Resolution: Unresolved Votes: 3
Labels: errormsgs, io

Attachments: File extend-io-factory-to-nil.diff    
Patch: Code and Test
Approval: Triaged

 Description   

This seems to a common idiom:

(clojure.java.io/reader (clojure.java.io/resource "myfile"))

When a file is available these are the behaviors:

=> (clojure.java.io/reader "resources/myfile")
#<BufferedReader java.io.BufferedReader@1f291df0>

=> (clojure.java.io/resource "myfile")
#<URL file:/project/resources/myfile>

=> (clojure.java.io/reader (clojure.java.io/resource "myfile"))
#<BufferedReader java.io.BufferedReader@1db04f7c>

If the file (resource) is unavailable:

=> (clojure.java.io/reader "resources/nofile")
FileNotFoundException resources/nofile (No such file or directory) java.io.FileInputStream.open (FileInputStream.java:-2)

=> (clojure.java.io/resource "nofile")
nil

=> (clojure.java.io/reader (clojure.java.io/resource "nofile"))
IllegalArgumentException No implementation of method: :make-reader of protocol: #'clojure.java.io/IOFactory found for class: nil clojure.core/-cache-protocol-fn (core_deftype.clj:541)

The main enhancement request is to have a better error message from `(clojure.java.io/reader nil)`. I'm not sure if io/resource should return something like 'resource "nofile" not found' or if io/reader could add a more helpful suggestion.



 Comments   
Comment by Alexander Redington [ 14/Feb/14 3:13 PM ]

This patch extends IOFactory to nil, providing error messages consistent with the default error messages provided for Object.

Comment by Benjamin Peter [ 15/Feb/14 1:31 PM ]

Looks like a good solution to me as a user. Thanks for the effort!

Comment by Dennis Schridde [ 12/Jul/14 2:01 AM ]

I would also be interested in a solution, as I am currently running into this with the ClojureScript compiler.

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