From 8950cf80586f691a3650204366450106afe350ee Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@mit.edu>
Date: Sat, 21 Jan 2017 15:30:40 -0500
Subject: [PATCH] support display of arbitrary textual MIME types in REPL,
 throw better error if show(io, MIME, x) is not defined during display
 (#19993)

---
 base/multimedia.jl | 63 ++++++++++++++++++++++++++++++----------------
 test/show.jl       | 12 +++++++++
 2 files changed, 54 insertions(+), 21 deletions(-)

diff --git a/base/multimedia.jl b/base/multimedia.jl
index 6756adad54846..54b1101f67826 100644
--- a/base/multimedia.jl
+++ b/base/multimedia.jl
@@ -141,9 +141,9 @@ displayable(mime::AbstractString) = displayable(MIME(mime))
 """
     TextDisplay(io::IO)
 
-Returns a `TextDisplay <: Display`, which can display any object as the text/plain MIME type
-(only), writing the text representation to the given I/O stream. (The text representation is
-the same as the way an object is printed in the Julia REPL.)
+Returns a `TextDisplay <: Display`, which displays any object as the text/plain MIME type
+(by default), writing the text representation to the given I/O stream. (This is how
+objects are printed in the Julia REPL.)
 """
 immutable TextDisplay <: Display
     io::IO
@@ -151,6 +151,13 @@ end
 display(d::TextDisplay, M::MIME"text/plain", x) = show(d.io, M, x)
 display(d::TextDisplay, x) = display(d, MIME"text/plain"(), x)
 
+# if you explicitly call display("text/foo", x), it should work on a TextDisplay:
+displayable(d::TextDisplay, M::MIME) = istextmime(M)
+function display(d::TextDisplay, M::MIME, x)
+    displayable(d, M) || throw(MethodError(display, (d, M, x)))
+    show(d.io, M, x)
+end
+
 import Base: close, flush
 flush(d::TextDisplay) = flush(d.io)
 close(d::TextDisplay) = close(d.io)
@@ -178,30 +185,32 @@ function reinit_displays()
     pushdisplay(TextDisplay(STDOUT))
 end
 
-macro try_display(expr)
-  quote
-    try $(esc(expr))
-    catch e
-      isa(e, MethodError) && e.f in (display, redisplay, show) ||
-        rethrow()
-    end
-  end
-end
-
 xdisplayable(D::Display, args...) = applicable(display, D, args...)
 
 function display(x)
     for i = length(displays):-1:1
-        xdisplayable(displays[i], x) &&
-            @try_display return display(displays[i], x)
+        if xdisplayable(displays[i], x)
+            try
+                return display(displays[i], x)
+            catch e
+                isa(e, MethodError) && e.f in (display, show) ||
+                  rethrow()
+            end
+        end
     end
     throw(MethodError(display, (x,)))
 end
 
 function display(m::MIME, x)
     for i = length(displays):-1:1
-        xdisplayable(displays[i], m, x) &&
-            @try_display return display(displays[i], m, x)
+        if xdisplayable(displays[i], m, x)
+            try
+                return display(displays[i], m, x)
+            catch e
+                isa(e, MethodError) && e.f == display ||
+                  rethrow()
+            end
+        end
     end
     throw(MethodError(display, (m, x)))
 end
@@ -226,16 +235,28 @@ end
 
 function redisplay(x)
     for i = length(displays):-1:1
-        xdisplayable(displays[i], x) &&
-            @try_display return redisplay(displays[i], x)
+        if xdisplayable(displays[i], x)
+            try
+                return redisplay(displays[i], x)
+            catch e
+                isa(e, MethodError) && e.f in (redisplay, display, show) ||
+                  rethrow()
+            end
+        end
     end
     throw(MethodError(redisplay, (x,)))
 end
 
 function redisplay(m::Union{MIME,AbstractString}, x)
     for i = length(displays):-1:1
-        xdisplayable(displays[i], m, x) &&
-            @try_display return redisplay(displays[i], m, x)
+        if xdisplayable(displays[i], m, x)
+            try
+                return redisplay(displays[i], m, x)
+            catch e
+                isa(e, MethodError) && e.f in (redisplay, display) ||
+                  rethrow()
+            end
+        end
     end
     throw(MethodError(redisplay, (m, x)))
 end
diff --git a/test/show.jl b/test/show.jl
index 09f140bc88d58..5838cfc4d23f6 100644
--- a/test/show.jl
+++ b/test/show.jl
@@ -630,3 +630,15 @@ end
 
 # don't use julia-specific `f` in Float32 printing (PR #18053)
 @test sprint(print, 1f-7) == "1.0e-7"
+
+# test that the REPL TextDisplay works for displaying arbitrary textual MIME types
+let d = TextDisplay(IOBuffer())
+    display(d, "text/csv", [3 1 4])
+    @test String(take!(d.io)) == "3,1,4\n"
+    @test_throws MethodError display(d, "text/foobar", [3 1 4])
+    try
+        display(d, "text/foobar", [3 1 4])
+    catch e
+        @test e.f == show
+    end
+end