Fix ;-escaping in the final history search segment

Let's also avoid copying the entirety of `str` when dropping escaped
characters while I'm at it.

Author: tecosaur

stdlib/REPL/src/History/resumablefiltering.jl

@@ -164,22 +164,27 @@ function ConditionSet(spec::S) where {S <: AbstractString}
         elseif chr == '\\'
             escaped = true
         elseif chr == FILTER_SEPARATOR
-            str = SubString(spec, mark:prevind(spec, pos))
-            if !isempty(dropbytes)
-                str = SubString(convert(S, String(deleteat!(collect(codeunits(str)), dropbytes))))
+            str = if isempty(dropbytes)
+                SubString(spec, mark:prevind(spec, pos))
+            else
+                subbytes = deleteat!(codeunits(spec)[mark:pos-1], dropbytes)
                 empty!(dropbytes)
+                SubString(convert(S, String(subbytes)))
             end
             addcond!(cset, lstrip(str))
             mark = pos + 1
         end
         pos = nextind(spec, pos)
     end
     if mark <= lastind
-        str = SubString(spec, mark:prevind(spec, pos))
-        if !isempty(dropbytes)
-            str = SubString(convert(S, String(deleteat!(collect(codeunits(str)), dropbytes))))
+        str = if isempty(dropbytes)
+            SubString(spec, mark)
+        else
+            subbytes = deleteat!(codeunits(spec)[mark:end], dropbytes)
+            empty!(dropbytes)
+            SubString(convert(S, String(subbytes)))
         end
-        addcond!(cset, lstrip(SubString(spec, mark:lastind)))
+        addcond!(cset, lstrip(str))
     end
     cset
 end

stdlib/REPL/test/history.jl

@@ -231,6 +231,8 @@ end
                 cset = ConditionSet("hello\\;world;=exact")
                 @test cset.words == [SubString("hello;world")]
                 @test cset.exacts == [SubString("exact")]
+                cset = ConditionSet("1 \\; 2")
+                @test cset.words == [SubString("1 ; 2")]
             end
             @testset "Complex query" begin
                 cset = ConditionSet("some = words ;; !error ; julia> ;/^def.*;")