REPL: implement Alt-{u,c,l} to change the case of the next word (#23379)

Fixes part of #8447.

base/repl/LineEdit.jl

@@ -636,6 +636,25 @@ function edit_transpose_words(buf::IOBuffer, mode=:emacs)
 end
 
 
+edit_upper_case(s) = edit_replace_word_right(s, uppercase)
+edit_lower_case(s) = edit_replace_word_right(s, lowercase)
+edit_title_case(s) = edit_replace_word_right(s, ucfirst)
+
+edit_replace_word_right(s, replace::Function) =
+    edit_replace_word_right(buffer(s), replace) && refresh_line(s)
+
+function edit_replace_word_right(buf::IOBuffer, replace::Function)
+    # put the cursor at the beginning of the next word
+    skipchars(buf, is_non_word_char)
+    b = position(buf)
+    char_move_word_right(buf)
+    e = position(buf)
+    e == b && return false
+    newstr = replace(String(buf.data[b+1:e]))
+    splice_buffer!(buf, b:e-1, newstr)
+    true
+end
+
 edit_clear(buf::IOBuffer) = truncate(buf, 0)
 
 function edit_clear(s::MIState)
@@ -1531,6 +1550,9 @@ AnyDict(
     end,
     "^T" => (s,o...)->edit_transpose_chars(s),
     "\et" => (s,o...)->edit_transpose_words(s),
+    "\eu" => (s,o...)->edit_upper_case(s),
+    "\el" => (s,o...)->edit_lower_case(s),
+    "\ec" => (s,o...)->edit_title_case(s),
 )
 
 const history_keymap = AnyDict(

doc/src/manual/interacting-with-julia.md

@@ -173,6 +173,9 @@ to do so).
 | `^K`                | "Kill" to end of line, placing the text in a buffer                                                        |
 | `^Y`                | "Yank" insert the text from the kill buffer                                                                |
 | `^T`                | Transpose the characters about the cursor                                                                  |
+| `meta-u`            | Change the next word to uppercase                                                                          |
+| `meta-c`            | Change the next word to titlecase                                                                          |
+| `meta-l`            | Change the next word to lowercase                                                                          |
 | `^Q`                | Write a number in REPL and press `^Q` to open editor at corresponding stackframe or method                 |
 
 

test/lineedit.jl

@@ -574,3 +574,15 @@ end
         @test bufferdata(s) == "begin\n" * ' '^(i-6) * "\n    x"
     end
 end
+
+@testset "change case on the right" begin
+    buf = IOBuffer()
+    LineEdit.edit_insert(buf, "aa bb CC")
+    seekstart(buf)
+    LineEdit.edit_upper_case(buf)
+    LineEdit.edit_title_case(buf)
+    @test String(take!(copy(buf))) == "AA Bb CC"
+    @test position(buf) == 5
+    LineEdit.edit_lower_case(buf)
+    @test String(take!(copy(buf))) == "AA Bb cc"
+end