Fix viewing of regions ending in multi-codepoint

We can't actually use view(content, region) as region spans the
codepoints of the string, but Julia expects the end of the range to be
the start not the end of the final codepoint.

Author: tecosaur

src/JuliaSyntaxHighlighting.jl

@@ -113,6 +113,7 @@ function _hl_annotations!(highlights::Vector{Tuple{UnitRange{Int}, Pair{Symbol,
     (; node, parent) = lineage
     (; content, offset, lnode, pdepths) = ctx
     region = firstindex(content)+offset:node.span+offset
+    regionstr = view(content, firstindex(content)+offset:prevind(content, node.span+offset+1))
     nkind = node.head.kind
     pnode = if !isnothing(parent) parent.node end
     pkind = if !isnothing(parent) kind(parent.node) end
@@ -129,7 +130,7 @@ function _hl_annotations!(highlights::Vector{Tuple{UnitRange{Int}, Pair{Symbol,
         if pkind == K"curly"
             :julia_type
         else
-            name = Symbol(view(content, region))
+            name = Symbol(regionstr)
             if name in SINGLETON_IDENTIFIERS
                 :julia_singleton_identifier
             elseif name == :NaN
@@ -220,14 +221,14 @@ function _hl_annotations!(highlights::Vector{Tuple{UnitRange{Int}, Pair{Symbol,
         if isnothing(arg1)
         elseif kind(arg1) == K"Identifier"
             region = first(region):first(region)+argoffset-1
-            name = Symbol(view(content, region))
+            name = Symbol(regionstr)
             ifelse(name in BUILTIN_FUNCTIONS, :julia_builtin, :julia_funcall)
         elseif kind(arg1) == K"." && length(arg1.args) == 3  &&
             kind(arg1.args[end]) == K"quote" &&
             length(arg1.args[end].args) == 1 &&
             kind(arg1.args[end].args[1]) == K"Identifier"
             region = first(region)+argoffset-arg1.args[end].args[1].span:first(region)+argoffset-1
-            name = Symbol(view(content, region))
+            name = Symbol(regionstr)
             ifelse(name in BUILTIN_FUNCTIONS, :julia_builtin, :julia_funcall)
         end
     elseif JuliaSyntax.is_error(nkind); :julia_error
@@ -254,13 +255,13 @@ function _hl_annotations!(highlights::Vector{Tuple{UnitRange{Int}, Pair{Symbol,
     if nkind == K"Comment"
         for match in eachmatch(
             r"(?:^|[(\[{[:space:]-])`([^[:space:]](?:.*?[^[:space:]])?)`(?:$|[!,\-.:;?\[\][:space:]])",
-            view(content, region))
+            regionstr)
             code = first(match.captures)
             push!(highlights, (firstindex(content)+offset+code.offset:firstindex(content)+offset+code.offset+code.ncodeunits-1,
                                :face => :code))
         end
     elseif nkind == K"String"
-        for match in eachmatch(r"\\.", view(content, region))
+        for match in eachmatch(r"\\.", regionstr)
             push!(highlights, (firstindex(content)+offset+match.offset-1:firstindex(content)+offset+match.offset+ncodeunits(match.match)-2,
                                :face => :julia_backslash_literal))
         end

test/runtests.jl

@@ -17,10 +17,13 @@ sum1to8_highlighted = Base.AnnotatedString("sum(1:8)", [
     (8:8, :face => :julia_rainbow_paren_1)
 ])
 
-@test highlight("sum(1:8)") ==sum1to8_highlighted
-@test highlight(IOBuffer("sum(1:8)")) ==sum1to8_highlighted
-@test highlight(IOContext(IOBuffer("sum(1:8)"))) ==sum1to8_highlighted
+@test highlight("sum(1:8)") == sum1to8_highlighted
+@test highlight(IOBuffer("sum(1:8)")) == sum1to8_highlighted
+@test highlight(IOContext(IOBuffer("sum(1:8)"))) == sum1to8_highlighted
 
 astr_sum1to8 = Base.AnnotatedString("sum(1:8)")
 @test highlight!(astr_sum1to8) == sum1to8_highlighted
 @test astr_sum1to8 == sum1to8_highlighted
+
+# Check for string indexing issues
+@test Base.annotations(highlight(":π")) |> first |> first == 1:3