Don't error when transposing an empty buffer (#46925)

JuliaLang · Sep 27, 2022 · 757f21e · 757f21e
1 parent cda61ef
commit 757f21e
Show file tree

Hide file tree

Showing 2 changed files with 10 additions and 1 deletion.
diff --git a/stdlib/REPL/src/LineEdit.jl b/stdlib/REPL/src/LineEdit.jl
@@ -1101,7 +1101,7 @@ end
 
 function edit_transpose_chars(buf::IOBuffer)
     # Moving left but not transpoing anything is intentional, and matches Emacs's behavior
-    eof(buf) && char_move_left(buf)
+    eof(buf) && position(buf) !== 0 && char_move_left(buf)
     position(buf) == 0 && return false
     char_move_left(buf)
     pos = position(buf)

diff --git a/stdlib/REPL/test/lineedit.jl b/stdlib/REPL/test/lineedit.jl
@@ -376,6 +376,8 @@ let buf = IOBuffer()
     LineEdit.edit_transpose_chars(buf)
     @test content(buf) == "βγαδε"
 
+
+    # Transposing a one-char buffer should behave like Emacs
     seek(buf, 0)
     @inferred(LineEdit.edit_clear(buf))
     edit_insert(buf, "a")
@@ -385,6 +387,13 @@ let buf = IOBuffer()
     LineEdit.edit_transpose_chars(buf)
     @test content(buf) == "a"
     @test position(buf) == 0
+
+    # Transposing an empty buffer shouldn't implode
+    seek(buf, 0)
+    LineEdit.edit_clear(buf)
+    LineEdit.edit_transpose_chars(buf)
+    @test content(buf) == ""
+    @test position(buf) == 0
 end
 
 @testset "edit_word_transpose" begin