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error message for (clojure.java.io/reader nil) — consistency for use with io/resource

Description

This seems to be 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) ;; EXPECTED: better error type/message

This situation would be improved with a better error message from `(clojure.java.io/reader nil)`.

Approach: Extend IOFactory to nil, providing error messages consistent with the default error messages provided for Object.

After:

user=> (clojure.java.io/reader (clojure.java.io/resource "nofile")) IllegalArgumentException Cannot open <nil> as a Reader. clojure.java.io/fn--9213 (io.clj:290)

Patch: clj-1210-2.patch

Environment

None

Attachments

2
  • 09 Oct 2015, 03:03 PM
  • 14 Feb 2014, 09:13 PM

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Benjamin Peter October 13, 2015 at 9:09 AM

Thanks a lot.

Alex Miller October 9, 2015 at 3:03 PM

Added -2 patch that makes commit message conform to expectations, no other changes, attribution retained.

import July 12, 2014 at 8:01 AM

Comment made by: devurandom

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

Benjamin Peter February 15, 2014 at 7:31 PM

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

Alexander Redington February 14, 2014 at 9:13 PM

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

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Created May 23, 2013 at 11:59 PM
Updated October 13, 2015 at 9:09 AM
Resolved October 13, 2015 at 9:09 AM