Implement eval-able AnnotatedString 2-arg show

The generic/fallback AbstractString 2-arg show omits the annotations, meaning that eval(Meta.parse(repr(::AnnotatedString))) doesn't round-trip. The resolution to this is fairly simple, we just need to implement a specialised show method. The implementation is fairly obvious, we're just also able to get away with hiding the vector type annotation since the constructor is fine without it.
JuliaLang · Apr 30, 2024 · b86fa13 · b86fa13
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diff --git a/base/strings/annotated.jl b/base/strings/annotated.jl
@@ -159,6 +159,22 @@ function getindex(s::AnnotatedString, i::Integer)
     end
 end
 
+# To make `AnnotatedString`s repr-evaluable, we need to override
+# the generic `AbstractString` 2-arg show method.
+
+function show(io::IO, s::A) where {A <: AnnotatedString}
+    show(io, A)
+    print(io, '(')
+    show(io, s.string)
+    print(io, ", ")
+    show(IOContext(io, :typeinfo => typeof(annotations(s))), annotations(s))
+    print(io, ')')
+end
+
+# But still use the generic `AbstractString` fallback for the 3-arg show.
+show(io::IO, ::MIME"text/plain", s::AnnotatedString) =
+    invoke(show, Tuple{IO, AbstractString}, io, s)
+
 ## AbstractChar interface ##
 
 ncodeunits(c::AnnotatedChar) = ncodeunits(c.char)

diff --git a/test/strings/annotated.jl b/test/strings/annotated.jl
@@ -58,6 +58,10 @@
                              (3:3, :val => 2)])),
              Base.AnnotatedString("abc", [(1:2, :val => 1),
                                   (2:3, :val => 2)]))
+    @test chopprefix(sprint(show, str), "Base.") ==
+        "AnnotatedString{String}(\"some string\", [(1:4, :thing => 0x01), (1:11, :all => 0x03), (6:11, :other => 0x02)])"
+    @test eval(Meta.parse(repr(str))) == str
+    @test sprint(show, str, MIME("text/plain")) == "\"some string\""
 end
 
 @testset "AnnotatedChar" begin