Use IOContexts instead of Base.have_color on 0.7

In Julia 0.7, whether an IO object supports color is a property of its
context; Base.have_color refers only to whether Julia was launched with
--color=yes. In 0.6, controlling color requires manipulating that global
flag. Thus we'll hack around the difference with version checking.

src/DeepDiffs.jl

@@ -13,6 +13,13 @@ function fieldequal(x::T, y::T) where T
     true
 end
 
+# Determine whether color is supported by the given stream
+@static if VERSION >= v"0.7.0-DEV.3077"
+    hascolor(io::IO) = get(IOContext(io), :color, false)
+else
+    hascolor(io::IO) = Base.have_color
+end
+
 """
 diff = deepdiff(obj1, obj2)
 

src/arrays.jl

@@ -110,7 +110,7 @@ end
 
 # prefix is printed if we're not using color
 function printitem(io, v, color=:normal, prefix="")
-    if Base.have_color
+    if hascolor(io)
         printstyled(io, v, color=color)
     else
         print(io, prefix, v)

src/strings.jl

@@ -62,7 +62,7 @@ function Base.show(io::IO, diff::StringDiff)
 
     print(io, "\"")
     visitall(diff.diff) do idx, state, last
-        if !Base.have_color
+        if !hascolor(io)
             # check to see if we need to close a block
             if laststate == :removed && state != :removed
                 print(io, "-}")
@@ -85,7 +85,7 @@ function Base.show(io::IO, diff::StringDiff)
         end
         laststate = state
     end
-    if !Base.have_color
+    if !hascolor(io)
         if laststate == :removed
             print(io, "-}")
         elseif laststate == :added

test/display.jl

@@ -1,4 +1,24 @@
 @testset "Display tests" begin
+    # Return a stream with color set as specified. On 0.6 this requires setting
+    # a global flag, and the :color property in the IOContext has no effect.
+    function setcolor(yn::Bool)
+        @static if VERSION < v"0.7.0-DEV.3077"
+            eval(Base, :(have_color = $yn))
+        end
+        IOContext(IOBuffer(), :color=>yn)
+    end
+
+    # Capture the original state of the global flag
+    orig_color = Base.have_color
+
+    function resetcolor()
+        @static if VERSION < v"0.7.0-DEV.3077"
+            global orig_color
+            eval(Base, :(have_color = $orig_color))
+        end
+        nothing
+    end
+
     # check dictionary print output. This is a little complicated because
     # the ordering isn't specified. To work around this we just split
     # up both into lines and make sure they have the same lines in some ordering.
@@ -10,34 +30,33 @@
         explines = sort(split(expected, "\n"))
         @test outlines == explines
     end
-    orig_color = Base.have_color
+
     @testset "Array diffs print correctly" begin
         d1 = deepdiff([1, 2, 7, 3], [2, 3, 4, 1, 2, 3, 5])
         d2 = deepdiff([1], [2])
 
-        buf = IOBuffer()
-        eval(Base, :(have_color=true))
+        buf = setcolor(true)
         expected1 = """
             [2, 3, 4, 1, 2, 7, 3, 5]"""
         expected2 = """[1, 2]"""
         @testset "Color Diffs" begin
             display(TextDisplay(buf), d1)
-            @test String(take!(buf)) == expected1
+            @test String(take!(buf.io)) == expected1
             display(TextDisplay(buf), d2)
-            @test String(take!(buf)) == expected2
+            @test String(take!(buf.io)) == expected2
         end
 
-        eval(Base, :(have_color=false))
+        buf = setcolor(false)
         @testset "No-Color Diffs" begin
             display(TextDisplay(buf), d1)
-            @test String(take!(buf)) == """
+            @test String(take!(buf.io)) == """
                 [(+)2, (+)3, (+)4, 1, 2, (-)7, 3, (+)5]"""
             display(TextDisplay(buf), d2)
-            @test String(take!(buf)) == """
+            @test String(take!(buf.io)) == """
                 [(-)1, (+)2]"""
         end
 
-        eval(Base, :(have_color=$orig_color))
+        resetcolor()
     end
 
     @testset "Dict diffs print correctly" begin
@@ -76,8 +95,7 @@
         )
 
         @testset "Color Diffs" begin
-            eval(Base, :(have_color=true))
-            buf = IOBuffer()
+            buf = setcolor(true)
             display(TextDisplay(buf), d)
             expected = """
             Dict(
@@ -101,11 +119,10 @@
             # This test is broken because the specifics of how the ANSI color
             # codes are printed change based on the order, which changes with
             # different julia versions.
-            @test_skip String(take!(buf)) == expected
+            @test_skip String(take!(buf.io)) == expected
         end
         @testset "No-Color Diffs" begin
-            eval(Base, :(have_color=false))
-            buf = IOBuffer()
+            buf = setcolor(false)
             display(TextDisplay(buf), d)
             expected = """
             Dict(
@@ -126,19 +143,19 @@
                  ),
             +    :e => "e",
             )"""
-            checkdictprint(String(take!(buf)), expected)
+            checkdictprint(String(take!(buf.io)), expected)
         end
-        eval(Base, :(have_color=$orig_color))
+
+        resetcolor()
     end
 
     @testset "single-line strings display correctly" begin
         # this test is just to handle some cases that don't get exercised elsewhere
         diff = deepdiff("abc", "adb")
-        buf = IOBuffer()
-        eval(Base, :(have_color=false))
+        buf = setcolor(false)
         display(TextDisplay(buf), diff)
-        @test String(take!(buf)) == "\"a{+d+}b{-c-}\""
-        eval(Base, :(have_color=true))
+        @test String(take!(buf.io)) == "\"a{+d+}b{-c-}\""
+        resetcolor()
     end
 
     @testset "Multi-line strings display correctly" begin
@@ -154,9 +171,8 @@
         multiline
         output"""
     diff = deepdiff(s1, s2)
-    buf = IOBuffer()
     @testset "Color Display" begin
-        eval(Base, :(have_color=true))
+        buf = setcolor(true)
         expected = """
         \"\"\"
           differences can
@@ -166,12 +182,12 @@
           multiline
           output\"\"\""""
         display(TextDisplay(buf), diff)
-        @test String(take!(buf)) == expected
+        @test String(take!(buf.io)) == expected
     end
     @testset "No-Color Display" begin
-        eval(Base, :(have_color=false))
+        buf = setcolor(false)
         display(TextDisplay(buf), diff)
-        @test String(take!(buf)) == """
+        @test String(take!(buf.io)) == """
         \"\"\"
           differences can
         - be hard to find
@@ -180,6 +196,6 @@
           multiline
           output\"\"\""""
     end
-    eval(Base, :(have_color=$orig_color))
+    resetcolor()
     end
 end