JLD.delete! removes JldDataset + stuff in _refs

doc/jld.md

@@ -22,6 +22,15 @@ close(file)
 This creates a dataset named `"A"` containing the contents of the variable `A`.
 There are also the convenient `save("mydata.jld", "A", A)` or `@save "mydata.jld" A` [syntaxes](../README.md).
 
+You may also use an array like syntax
+```julia
+file = jldopen("mydata.jld", "w")
+file["a"] = [1:100]
+b = file["a"][20:30]
+close(file)
+```
+Use the `delete!` function to delete `JldDataset`s and their associated references.  Directly deleting a `JldDataset` with `o_delete` will leave behind unwanted objects that may cause future errors, especially if you reuse the same path in the JLD file. 
+
 JLD files can be opened with the `mmaparrays` option, which if true returns "qualified" array data sets as arrays using [memory-mapping](hdf5.md#memory-mapping):
 
 ```julia

src/jld.jl

@@ -7,7 +7,7 @@ using HDF5
 # Add methods to...
 import HDF5: close, dump, exists, file, getindex, setindex!, g_create, g_open, o_delete, name, names, read, size, write,
              HDF5ReferenceObj, HDF5BitsKind, ismmappable, readmmap
-import Base: length, endof, show, done, next, start
+import Base: length, endof, show, done, next, start, delete!
 
 if !isdefined(:setfield!)
     const setfield! = setfield
@@ -197,6 +197,12 @@ name(p::Union(JldFile, JldGroup, JldDataset)) = name(p.plain)
 exists(p::Union(JldFile, JldGroup, JldDataset), path::ByteString) = exists(p.plain, path)
 root(p::Union(JldFile, JldGroup, JldDataset)) = g_open(file(p), "/")
 o_delete(parent::Union(JldFile, JldGroup), args...) = o_delete(parent.plain, args...)
+function delete!(g::Union(JldGroup, JldFile), name)
+    beginswith(name,'_') && error("$name is internal to the JLD format, use o_delete if you really want to delete it")
+    o_delete(g, name)
+    o_delete(g, joinpath("_refs", name))
+end
+delete!(parent::Union(JldFile, JldGroup), args...) = for a in args delete!(parent,a) end
 ismmappable(obj::JldDataset) = ismmappable(obj.plain)
 readmmap(obj::JldDataset, args...) = readmmap(obj.plain, args...)
 setindex!(parent::Union(JldFile, JldGroup), val, path::ASCIIString) = write(parent, path, val)

test/jld.jl

@@ -1,5 +1,6 @@
 using HDF5
 using JLD
+using Base.Test
 
 # Define variables of different types
 x = 3.7
@@ -296,14 +297,23 @@ save(fn, "i106", Mod106.typ(1, Mod106.UnexportedT))
 i106 = load(fn, "i106")
 @assert i106 == Mod106.typ(1, Mod106.UnexportedT)
 
-# bracket synax for datasets
+# bracket synax for datasets + delete!
 jldopen(fn, "w") do file
     file["a"] = [1:100]
     file["b"] = [x*y for x=1:10,y=1:10]
+    file["ms"] = ms
+    delete!(file, "ms")
+    file["ms"] = β
+    g_create(file,"g")
+    file["g/ms"] = ms
+    @test_throws ErrorException delete!(file, "_refs/g/ms")
+    delete!(file, "g/ms")
 end
 jldopen(fn, "r") do file
     @assert(file["a"][1:50] == [1:50])
     @assert(file["b"][5,6][1]==5*6)
+    @assert(read(file["ms"]) == β)
+    @assert(!exists(file, "g/ms"))
 end
 
 # bracket syntax when created by HDF5