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[CLJ-1187] Clojure loses quoted metadata on empty literals Created: 22/Mar/13  Updated: 06/Jul/14  Resolved: 06/Jul/14

Status: Closed
Project: Clojure
Component/s: None
Affects Version/s: Release 1.5, Release 1.6
Fix Version/s: Release 1.7

Type: Defect Priority: Minor
Reporter: Nicola Mometto Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None

Attachments: Text File 001-CLJ-1187.patch    
Patch: Code and Test
Approval: Vetted


meta on empty collections is lost:

user=> (meta '^:foo [])
nil   ;; expected {:foo true} as in:
user=> (meta '^:foo [1])
{:foo true}

This bug propagates to ^:const vars:

user=> (def ^:const foo ^:foo [])
user=> (meta foo)
user=> (meta @#'foo)
{:foo true}

Cause: As in CLJ-1093, empty collections are replaced with an EmptyExpr that loses meta

Proposed: Don't replace with EmptyExpr if meta is present.

Patch: 001-CLJ-1187.patch (NOTE: this change overlaps with CLJ-1093 and the patch there may be preferred)

Screened by:

Comment by Nicola Mometto [ 22/Mar/13 2:12 PM ]

After patch:

user=> (meta '^:foo [])
{:foo true}
user=> (meta '^:foo [:a])
{:foo true}
user=> (def ^:const foo ^:foo [])
user=> (meta foo)
{:foo true}

Comment by Stuart Halloway [ 29/Mar/13 6:13 AM ]

I believe the title should read "Clojure loses quoted metdata on empty literals".

Comment by Stuart Halloway [ 29/Mar/13 6:16 AM ]

At first glance, the implementation looks wrong in that it blocks non-IObjs ever getting to EmptyExpr. Probably all persistent collections are IObjs, but would not want to bake this in.

Comment by Nicola Mometto [ 29/Mar/13 7:00 AM ]

You're right, I've updated my patch, it should work as expected now

Comment by Andy Fingerhut [ 04/Apr/13 9:44 PM ]

Nicola: Your updated patch 001-CLJ-1187.patch dated Mar 29, 2013 gives syntax errors when I try to compile it.

Comment by Nicola Mometto [ 05/Apr/13 9:06 AM ]

Oh, the irony, I messed up some parentheses writing java.

Sorry for it, here's the correct patch, it applies on upstream/master.

Comment by Gabriel Horner [ 24/May/13 9:14 AM ]

Looks good

Comment by Nicola Mometto [ 26/Jun/13 8:08 PM ]

CLJ-1093 contains a patch that fixes this issue aswell and should be preferred

Comment by Alex Miller [ 18/Aug/13 2:46 PM ]

Marking un-Screened due to the note about CLJ-1093. Want to assess this more before going through Rich.

Comment by Alex Miller [ 18/Oct/13 8:49 AM ]

Switching to Incomplete pending CLJ-1093 which I hope to pull into 1.6.

Comment by Alex Miller [ 17/Jan/14 10:17 AM ]

Pulling out of 1.6, will consider in next release.

Comment by Alex Miller [ 06/Jul/14 6:25 PM ]

Dupe of CLJ-1093, closed at Nicola's request.

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