Don't give public but unexported symbols as repl completions in an un…

…qualified context (#51345)

stdlib/REPL/src/REPLCompletions.jl

@@ -136,6 +136,7 @@ end
 
 function filtered_mod_names(ffunc::Function, mod::Module, name::AbstractString, all::Bool = false, imported::Bool = false)
     ssyms = names(mod, all = all, imported = imported)
+    all || filter!(Base.Fix1(Base.isexported, mod), ssyms)
     filter!(ffunc, ssyms)
     macros = filter(x -> startswith(String(x), "@" * name), ssyms)
     syms = String[sprint((io,s)->Base.show_sym(io, s; allow_macroname=true), s) for s in ssyms if completes_global(String(s), name)]

stdlib/REPL/test/replcompletions.jl

@@ -1896,3 +1896,17 @@ let s = "Issue49892(fal"
         @test n in c
     end
 end
+
+@testset "public but non-exported symbols only complete qualified (#51331)" begin
+    c, r, res = test_complete("ispub")
+    @test res
+    @test "ispublic" ∉ c
+
+    c, r, res = test_complete("Base.ispub")
+    @test res
+    @test "ispublic" ∈ c
+
+    @test Base.ispublic(Base, :ispublic)
+    # If this last test starts failing, that's okay, just pick a new example symbol:
+    @test !Base.isexported(Base, :ispublic)
+end