Render Symbols with repr in duplicate-name error message

src/other/index.jl

@@ -45,7 +45,7 @@ function rename!(x::Index, nms::AbstractVector{Symbol}; makeunique::Bool=false)
     if !makeunique
         if length(unique(nms)) != length(nms)
             dup = unique(nms[nonunique(DataFrame(nms=nms))])
-            dupstr = join(string.(':', dup), ", ", " and ")
+            dupstr = join(repr.(dup), ", ", " and ")
             msg = "Duplicate variable names: $dupstr. Pass makeunique=true " *
                   "to make them unique using a suffix automatically."
             throw(ArgumentError(msg))
@@ -463,7 +463,7 @@ function add_names(ind::Index, add_ind::AbstractIndex; makeunique::Bool=false)
     end
     if length(dups) > 0
         if !makeunique
-            dupstr = join(string.(':', unique(u[dups])), ", ", " and ")
+            dupstr = join(repr.(unique(u[dups])), ", ", " and ")
             msg = "Duplicate variable names: $dupstr. Pass makeunique=true " *
                   "to make them unique using a suffix automatically."
             throw(ArgumentError(msg))

src/other/utils.jl

@@ -93,7 +93,7 @@ function make_unique!(names::Vector{Symbol}, src::AbstractVector{Symbol};
 
     if length(dups) > 0
         if !makeunique
-            dupstr = join(string.(':', unique(src[dups])), ", ", " and ")
+            dupstr = join(repr.(unique(src[dups])), ", ", " and ")
             msg = "Duplicate variable names: $dupstr. Pass makeunique=true " *
                   "to make them unique using a suffix automatically."
             throw(ArgumentError(msg))

test/utils.jl

@@ -8,6 +8,30 @@ using Test, Random, DataFrames
     @test DataFrames.make_unique([:x, :x_1, :x2], makeunique=false) == [:x, :x_1, :x2]
 end
 
+@testset "duplicate-name error message uses repr for Symbols" begin
+    # this testset was AI generated
+    # Identifier-like Symbols still render as `:name`.
+    err = try DataFrames.make_unique([:a, :a]) catch e; e end
+    @test err isa ArgumentError
+    @test occursin(":a", err.msg)
+
+    # Symbols containing characters that aren't valid in an identifier
+    # must use the explicit `Symbol("...")` form so the message is
+    # unambiguous (previously rendered as `:column name`, which
+    # reads like a parse error rather than naming a single Symbol).
+    s = Symbol("column name")
+    for thunk in (
+        () -> DataFrames.make_unique([s, s]),                  # src/other/utils.jl
+        () -> rename!(DataFrames.Index([:a, :b]), [s, s]),     # src/other/index.jl rename!
+        () -> hcat(DataFrame(s => 1), DataFrame(s => 2)),      # src/other/index.jl add_names
+    )
+        err = try thunk() catch e; e end
+        @test err isa ArgumentError
+        @test occursin("Symbol(\"column name\")", err.msg)
+        @test !occursin(":column name", err.msg)
+    end
+end
+
 @testset "repeat count" begin
     df = DataFrame(a=1:2, b=3:4)
     ref = DataFrame(a=repeat(1:2, 2),