Add do-block support for redirect_std[out,err,in]

Fixes JuliaLang#7022. In particular, these simplify testing for warnings.

base/docs/helpdb/Base.jl

@@ -3936,14 +3936,6 @@ Convert `x` from degrees to radians.
 """
 deg2rad
 
-"""
-    redirect_stdin([stream])
-
-Like redirect_stdout, but for STDIN. Note that the order of the return tuple is still
-(rd,wr), i.e. data to be read from STDIN, may be written to wr.
-"""
-redirect_stdin
-
 """
     mktemp([parent=tempdir()])
 
@@ -5196,13 +5188,6 @@ The result of an expression is too large for the specified type and will cause a
 """
 OverflowError
 
-"""
-    redirect_stderr([stream])
-
-Like `redirect_stdout`, but for `STDERR`.
-"""
-redirect_stderr
-
 """
     ctranspose!(dest,src)
 
@@ -6759,24 +6744,6 @@ General unescaping of traditional C and Unicode escape sequences. Reverse of
 """
 unescape_string(s)
 
-"""
-    redirect_stdout()
-
-Create a pipe to which all C and Julia level `STDOUT` output will be redirected. Returns a
-tuple `(rd,wr)` representing the pipe ends. Data written to `STDOUT` may now be read from
-the rd end of the pipe. The wr end is given for convenience in case the old `STDOUT` object
-was cached by the user and needs to be replaced elsewhere.
-"""
-redirect_stdout
-
-"""
-    redirect_stdout(stream)
-
-Replace `STDOUT` by stream for all C and Julia level output to `STDOUT`. Note that `stream`
-must be a TTY, a `Pipe` or a `TCPSocket`.
-"""
-redirect_stdout(stream)
-
 """
     print_with_color(color::Symbol, [io], strings...)
 

base/stream.jl

@@ -955,6 +955,74 @@ for (x, writable, unix_fd, c_symbol) in
     end
 end
 
+"""
+    redirect_stdout()
+
+Create a pipe to which all C and Julia level `STDOUT` output will be redirected. Returns a
+tuple `(rd,wr)` representing the pipe ends. Data written to `STDOUT` may now be read from
+the rd end of the pipe. The wr end is given for convenience in case the old `STDOUT` object
+was cached by the user and needs to be replaced elsewhere.
+"""
+redirect_stdout
+
+"""
+    redirect_stdout(stream)
+
+Replace `STDOUT` by stream for all C and Julia level output to `STDOUT`. Note that `stream`
+must be a TTY, a `Pipe` or a `TCPSocket`.
+"""
+redirect_stdout(stream)
+
+"""
+    redirect_stderr([stream])
+
+Like `redirect_stdout`, but for `STDERR`.
+"""
+redirect_stderr
+
+"""
+    redirect_stdin([stream])
+
+Like redirect_stdout, but for STDIN. Note that the order of the return tuple is still
+(rd,wr), i.e. data to be read from STDIN, may be written to wr.
+"""
+redirect_stdin
+
+for (F,S) in ((:redirect_stdin, :STDIN), (:redirect_stdout, :STDOUT), (:redirect_stderr, :STDERR))
+    @eval function $F(f::Function, stream)
+        STDOLD = $S
+        local ret
+        $F(stream)
+        try
+            ret = f()
+        finally
+            $F(STDOLD)
+        end
+        ret
+    end
+end
+
+"""
+    redirect_stdout(f::Function, stream)
+
+Run the function `f` while redirecting `STDOUT` to `stream`. Upon completion, `STDOUT` is restored to its prior setting.
+"""
+redirect_stdout(f::Function, stream)
+
+"""
+    redirect_stderr(f::Function, stream)
+
+Run the function `f` while redirecting `STDERR` to `stream`. Upon completion, `STDERR` is restored to its prior setting.
+"""
+redirect_stderr(f::Function, stream)
+
+"""
+    redirect_stdin(f::Function, stream)
+
+Run the function `f` while redirecting `STDIN` to `stream`. Upon completion, `STDIN` is restored to its prior setting.
+"""
+redirect_stdin(f::Function, stream)
+
 mark(x::LibuvStream)     = mark(x.buffer)
 unmark(x::LibuvStream)   = unmark(x.buffer)
 reset(x::LibuvStream)    = reset(x.buffer)

doc/stdlib/io-network.rst

@@ -350,18 +350,36 @@ General I/O
 
    Replace ``STDOUT`` by stream for all C and Julia level output to ``STDOUT``\ . Note that ``stream`` must be a TTY, a ``Pipe`` or a ``TCPSocket``\ .
 
+.. function:: redirect_stdout(f::Function, stream)
+
+   .. Docstring generated from Julia source
+
+   Run the function ``f`` while redirecting ``STDOUT`` to ``stream``\ . Upon completion, ``STDOUT`` is restored to its prior setting.
+
 .. function:: redirect_stderr([stream])
 
    .. Docstring generated from Julia source
 
    Like ``redirect_stdout``\ , but for ``STDERR``\ .
 
+.. function:: redirect_stderr(f::Function, stream)
+
+   .. Docstring generated from Julia source
+
+   Run the function ``f`` while redirecting ``STDERR`` to ``stream``\ . Upon completion, ``STDERR`` is restored to its prior setting.
+
 .. function:: redirect_stdin([stream])
 
    .. Docstring generated from Julia source
 
    Like redirect_stdout, but for STDIN. Note that the order of the return tuple is still (rd,wr), i.e. data to be read from STDIN, may be written to wr.
 
+.. function:: redirect_stdin(f::Function, stream)
+
+   .. Docstring generated from Julia source
+
+   Run the function ``f`` while redirecting ``STDIN`` to ``stream``\ . Upon completion, ``STDIN`` is restored to its prior setting.
+
 .. function:: readchomp(x)
 
    .. Docstring generated from Julia source

test/show.jl

@@ -318,6 +318,32 @@ let oldout = STDOUT, olderr = STDERR
     end
 end
 
+let filename = tempname()
+    ret = open(filename, "w") do f
+        redirect_stdout(f) do
+            println("hello")
+            [1,3]
+        end
+    end
+    @test ret == [1,3]
+    @test chomp(readstring(filename)) == "hello"
+    ret = open(filename, "w") do f
+        redirect_stderr(f) do
+            warn("hello")
+            [2]
+        end
+    end
+    @test ret == [2]
+    @test contains(readstring(filename), "WARNING: hello")
+    ret = open(filename) do f
+        redirect_stdin(f) do
+            readline()
+        end
+    end
+    @test contains(ret, "WARNING: hello")
+    rm(filename)
+end
+
 # issue #12960
 type T12960 end
 let
@@ -576,4 +602,4 @@ end
 # Test compact printing of homogeneous tuples
 @test repr(NTuple{7,Int64}) == "NTuple{7,Int64}"
 @test repr(Tuple{Float64, Float64, Float64, Float64}) == "NTuple{4,Float64}"
-@test repr(Tuple{Float32, Float32, Float32}) == "Tuple{Float32,Float32,Float32}"
+@test repr(Tuple{Float32, Float32, Float32}) == "Tuple{Float32,Float32,Float32}"