Take into account color and unicode in matrix alignment (#45751)

Without this, alignment would count characters rather than
textwidth as well as counting inline escape sequences in
colored output. Fix that by using uncolored printing for
alignment and textwidth rather than number of codepoints.

base/show.jl

@@ -2783,6 +2783,9 @@ function dump(arg; maxdepth=DUMP_DEFAULT_MAXDEPTH)
     dump(IOContext(stdout::IO, :limit => true, :module => mod), arg; maxdepth=maxdepth)
 end
 
+nocolor(io::IO) = IOContext(io, :color => false)
+alignment_from_show(io::IO, x::Any) =
+    textwidth(sprint(show, x, context=nocolor(io), sizehint=0))
 
 """
 `alignment(io, X)` returns a tuple (left,right) showing how many characters are
@@ -2800,35 +2803,38 @@ julia> Base.alignment(stdout, 1 + 10im)
 (3, 5)
 ```
 """
-alignment(io::IO, x::Any) = (0, length(sprint(show, x, context=io, sizehint=0)))
-alignment(io::IO, x::Number) = (length(sprint(show, x, context=io, sizehint=0)), 0)
-alignment(io::IO, x::Integer) = (length(sprint(show, x, context=io, sizehint=0)), 0)
+alignment(io::IO, x::Any) = (0, alignment_from_show(io, x))
+alignment(io::IO, x::Number) = (alignment_from_show(io, x), 0)
+alignment(io::IO, x::Integer) = (alignment_from_show(io, x), 0)
 function alignment(io::IO, x::Real)
-    m = match(r"^(.*?)((?:[\.eEfF].*)?)$", sprint(show, x, context=io, sizehint=0))
-    m === nothing ? (length(sprint(show, x, context=io, sizehint=0)), 0) :
-                   (length(m.captures[1]), length(m.captures[2]))
+    s = sprint(show, x, context=nocolor(io), sizehint=0)
+    m = match(r"^(.*?)((?:[\.eEfF].*)?)$", s)
+    m === nothing ? (textwidth(s), 0) :
+                    (textwidth(m.captures[1]), textwidth(m.captures[2]))
 end
 function alignment(io::IO, x::Complex)
-    m = match(r"^(.*[^ef][\+\-])(.*)$", sprint(show, x, context=io, sizehint=0))
-    m === nothing ? (length(sprint(show, x, context=io, sizehint=0)), 0) :
-                   (length(m.captures[1]), length(m.captures[2]))
+    s = sprint(show, x, context=nocolor(io), sizehint=0)
+    m = match(r"^(.*[^ef][\+\-])(.*)$", s)
+    m === nothing ? (textwidth(s), 0) :
+                    (textwidth(m.captures[1]), textwidth(m.captures[2]))
 end
 function alignment(io::IO, x::Rational)
-    m = match(r"^(.*?/)(/.*)$", sprint(show, x, context=io, sizehint=0))
-    m === nothing ? (length(sprint(show, x, context=io, sizehint=0)), 0) :
-                   (length(m.captures[1]), length(m.captures[2]))
+    s = sprint(show, x, context=nocolor(io), sizehint=0)
+    m = match(r"^(.*?/)(/.*)$", s)
+    m === nothing ? (textwidth(s), 0) :
+                    (textwidth(m.captures[1]), textwidth(m.captures[2]))
 end
 
 function alignment(io::IO, x::Pair)
-    s = sprint(show, x, context=io, sizehint=0)
+    fullwidth = alignment_from_show(io, x)
     if !isdelimited(io, x) # i.e. use "=>" for display
         ctx = IOContext(io, :typeinfo => gettypeinfos(io, x)[1])
-        left = length(sprint(show, x.first, context=ctx, sizehint=0))
+        left = alignment_from_show(ctx, x.first)
         left += 2 * !isdelimited(ctx, x.first) # for parens around p.first
         left += !(get(io, :compact, false)::Bool) # spaces are added around "=>"
-        (left+1, length(s)-left-1) # +1 for the "=" part of "=>"
+        (left+1, fullwidth-left-1) # +1 for the "=" part of "=>"
     else
-        (0, length(s)) # as for x::Any
+        (0, fullwidth) # as for x::Any
     end
 end
 

test/show.jl

@@ -2360,3 +2360,16 @@ end
     @test sprint(show, setenv(setcpuaffinity(`true`, [1, 2]), "A" => "B")) ==
           """setenv(setcpuaffinity(`true`, [1, 2]),["A=B"])"""
 end
+
+# Test that alignment takes into account unicode and computes alignment without
+# color/formatting.
+
+struct ColoredLetter; end
+Base.show(io::IO, ces::ColoredLetter) = Base.printstyled(io, 'A'; color=:red)
+
+struct ⛵; end
+Base.show(io::IO, ces::⛵) = Base.print(io, '⛵')
+
+@test Base.alignment(stdout, ⛵()) == (0, 2)
+@test Base.alignment(IOContext(IOBuffer(), :color=>true), ColoredLetter()) == (0, 1)
+@test Base.alignment(IOContext(IOBuffer(), :color=>false), ColoredLetter()) == (0, 1)