deprecate String(io::IOBuffer). fixes #21438

NEWS.md

@@ -175,6 +175,8 @@ Deprecated or removed
   * The forms of `read`, `readstring`, and `eachline` that accepted both a `Cmd` object and an
     input stream are deprecated. Use e.g. `read(pipeline(stdin, cmd))` instead ([#22762]).
 
+  * The method `String(io::IOBuffer)` is deprecated to `String(take!(copy(io)))` ([#21438]).
+
 
 Julia v0.6.0 Release Notes
 ==========================

base/deprecated.jl

@@ -1587,6 +1587,8 @@ end
 @deprecate readstring(cmd::AbstractCmd, stdin::Redirectable) readstring(pipeline(stdin, cmd))
 @deprecate eachline(cmd::AbstractCmd, stdin; chomp::Bool=true) eachline(pipeline(stdin, cmd), chomp=chomp)
 
+@deprecate String(io::AbstractIOBuffer) String(take!(copy(io)))
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/iobuffer.jl

@@ -257,12 +257,6 @@ end
 
 isopen(io::AbstractIOBuffer) = io.readable || io.writable || io.seekable || nb_available(io) > 0
 
-function String(io::AbstractIOBuffer)
-    io.readable || throw(ArgumentError("IOBuffer is not readable"))
-    io.seekable || throw(ArgumentError("IOBuffer is not seekable"))
-    return unsafe_string(pointer(io.data), io.size)
-end
-
 """
     take!(b::IOBuffer)
 

test/dict.jl

@@ -301,7 +301,7 @@ let d = Dict((1=>2) => (3=>45), (3=>10) => (10=>11))
 
     # Check explicitly for the expected strings, since the CPU bitness effects
     # dictionary ordering.
-    result = String(buf)
+    result = String(take!(buf))
     @test contains(result, "Dict")
     @test contains(result, "(1=>2)=>(3=>45)")
     @test contains(result, "(3=>10)=>(10=>11)")

test/iobuffer.jl

@@ -2,6 +2,8 @@
 
 ioslength(io::IOBuffer) = (io.seekable ? io.size : nb_available(io))
 
+bufcontents(io::AbstractIOBuffer) = unsafe_string(pointer(io.data), io.size)
+
 let io = IOBuffer()
 @test eof(io)
 @test_throws EOFError read(io,UInt8)
@@ -17,7 +19,7 @@ seek(io, 0)
 a = Array{UInt8}(2)
 @test read!(io, a) == a
 @test a == UInt8['b','c']
-@test String(io) == "abc"
+@test bufcontents(io) == "abc"
 seek(io, 1)
 truncate(io, 2)
 @test position(io) == 1
@@ -178,7 +180,7 @@ let io=IOBuffer(SubString("***αhelloworldω***",4,16)), io2 = IOBuffer(b"goodni
     @test_throws EOFError read(io,UInt8)
     skip(io, -3)
     @test readstring(io) == "dω"
-    @test String(io) == "αhelloworldω"
+    @test bufcontents(io) == "αhelloworldω"
     @test_throws ArgumentError write(io,"!")
     @test take!(io) == b"αhelloworldω"
     seek(io, 2)
@@ -193,7 +195,7 @@ let io=IOBuffer(SubString("***αhelloworldω***",4,16)), io2 = IOBuffer(b"goodni
     seek(io2, 0)
     write(io2, io2)
     @test readstring(io2) == ""
-    @test String(io2) == "goodnightmoonhelloworld"
+    @test bufcontents(io2) == "goodnightmoonhelloworld"
 end
 
 # issue #11917

test/repl.jl

@@ -677,7 +677,7 @@ function history_move_prefix(s::LineEdit.MIState,
     buf = LineEdit.buffer(s)
     pos = position(buf)
     prefix = REPL.beforecursor(buf)
-    allbuf = String(buf)
+    allbuf = String(take!(copy(buf)))
     cur_idx = hist.cur_idx
     # when searching forward, start at last_idx
     if !backwards && hist.last_idx > 0

test/replutil.jl

@@ -450,7 +450,7 @@ let d = Dict(1 => 2, 3 => 45)
     buf = IOBuffer()
     td = TextDisplay(buf)
     display(td, d)
-    result = String(td.io)
+    result = String(take!(td.io))
 
     @test contains(result, summary(d))
 
@@ -466,13 +466,13 @@ let err, buf = IOBuffer()
     try Array() catch err end
     Base.show_method_candidates(buf,err)
     @test isa(err, MethodError)
-    @test contains(String(buf), "Closest candidates are:")
+    @test contains(String(take!(buf)), "Closest candidates are:")
 end
 
 # Issue 20111
 let K20111(x) = y -> x, buf = IOBuffer()
     show(buf, methods(K20111(1)))
-    @test contains(String(buf), " 1 method for generic function")
+    @test contains(String(take!(buf)), " 1 method for generic function")
 end
 
 # @macroexpand tests