add support for automatic bracket completion in REPL input (#59847)

Author: KristofferC

NEWS.md

@@ -98,6 +98,7 @@ Standard library changes
 
 * The Julia REPL now support bracketed paste on Windows which should significantly speed up pasting large code blocks into the REPL ([#59825])
 * The REPL now provides syntax highlighting for input as you type. See the REPL docs for more info about customization.
+* The REPL now supports automatic insertion of closing brackets, parentheses, and quotes. See the REPL docs for more info about customization.
 * The display of `AbstractChar`s in the main REPL mode now includes LaTeX input information like what is shown in help mode ([#58181]).
 * Display of repeated frames and cycles in stack traces has been improved by bracketing them in the trace and treating them consistently ([#55841]).
 

stdlib/REPL/docs/src/index.md

@@ -317,6 +317,28 @@ atreplinit(customize_keys)
 
 Users should refer to `LineEdit.jl` to discover the available actions on key input.
 
+### Automatic bracket insertion
+
+The Julia REPL supports automatically inserting closing brackets, parentheses, braces, and quotes
+when you type the opening character.
+
+When enabled, typing an opening bracket `(`, `{`, or `[` will automatically insert the matching
+closing bracket `)`, `}`, or `]` and position the cursor between them. The same behavior applies
+to quotes (`"`, `'`, and `` ` ``). If you then type the closing character, the REPL will skip over
+the auto-inserted character instead of inserting a duplicate. Additionally, pressing backspace
+immediately after auto-insertion will remove both the opening and closing characters.
+
+To disable this feature, add the following to your `~/.julia/config/startup.jl` file:
+
+```julia
+atreplinit() do repl
+    # Robust against older julia versions
+    if hasfield(typeof(repl.options), :auto_insert_closing_bracket)
+        repl.options.auto_insert_closing_bracket = false
+    end
+end
+```
+
 ## Tab completion
 
 In the Julian, pkg and help modes of the REPL, one can enter the first few characters of a function

stdlib/REPL/src/LineEdit.jl

@@ -2101,6 +2101,142 @@ const escape_defaults = merge!(
     AnyDict("\e[$(c)l" => nothing for c in 1:20)
     )
 
+
+# Keymap for automatic bracket/quote insertion and completion
+const bracket_insert_keymap = AnyDict()
+let
+    # Determine when we should not close a bracket/quote
+    function should_skip_closing_bracket(left_peek, v)
+        # Don't close if we already have an open quote immediately before (triple quote case)
+        # For quotes, also check for transpose expressions: issue JuliaLang/OhMyREPL.jl#200
+        left_peek == v && return true
+        if v == '\''
+            tr_expr = isletter(left_peek) || isnumeric(left_peek) || left_peek == '_' || left_peek == ']'
+            return tr_expr
+        end
+        return false
+    end
+
+    function peek_char_left(b::IOBuffer)
+        p = position(b)
+        c = char_move_left(b)
+        seek(b, p)
+        return c
+    end
+
+    # Check if there's an unmatched opening quote before the cursor
+    function has_unmatched_quote(buf::IOBuffer, quote_char::Char)
+        pos = position(buf)
+        content = String(buf.data[1:pos])
+        isempty(content) && return false
+
+        # Count unescaped quotes before cursor position
+        count = 0
+        i = 1
+        while i <= length(content)
+            if content[i] == quote_char
+                # Check if escaped by counting preceding backslashes
+                num_backslashes = 0
+                j = i - 1
+                while j >= 1 && content[j] == '\\'
+                    num_backslashes += 1
+                    j -= 1
+                end
+                # If even number of backslashes (including zero), the quote is not escaped
+                if num_backslashes % 2 == 0
+                    count += 1
+                end
+            end
+            i = nextind(content, i)
+        end
+        return isodd(count)
+    end
+
+    # Left/right bracket pairs
+    bracket_pairs = (('(', ')'), ('{', '}'), ('[', ']'))
+    right_brackets_ws = (')', '}', ']', ' ', '\t', '\n')
+
+    for (left, right) in bracket_pairs
+        # Left bracket: insert both and move cursor between them
+        bracket_insert_keymap[left] = (s::MIState, o...) -> begin
+            buf = buffer(s)
+            edit_insert(buf, left)
+            if eof(buf) || peek(buf, Char) in right_brackets_ws
+                edit_insert(buf, right)
+                edit_move_left(buf)
+            end
+            refresh_line(s)
+        end
+
+        # Right bracket: skip over if next char matches, otherwise insert
+        bracket_insert_keymap[right] = (s::MIState, o...) -> begin
+            buf = buffer(s)
+            if !eof(buf) && peek(buf, Char) == right
+                edit_move_right(buf)
+            else
+                edit_insert(buf, right)
+            end
+            refresh_line(s)
+        end
+    end
+
+    # Quote characters (need special handling for transpose detection)
+    for quote_char in ('"', '\'', '`')
+        bracket_insert_keymap[quote_char] = (s::MIState, o...) -> begin
+            buf = buffer(s)
+            if !eof(buf) && peek(buf, Char) == quote_char
+                # Skip over closing quote
+                edit_move_right(buf)
+            elseif position(buf) > 0 && should_skip_closing_bracket(peek_char_left(buf), quote_char)
+                # Don't auto-close (e.g., for transpose or triple quotes)
+                edit_insert(buf, quote_char)
+            elseif quote_char in ('"', '\'', '`') && has_unmatched_quote(buf, quote_char)
+                # For quotes, check if we're closing an existing string
+                edit_insert(buf, quote_char)
+            else
+                # Insert both quotes
+                edit_insert(buf, quote_char)
+                edit_insert(buf, quote_char)
+                edit_move_left(buf)
+            end
+            refresh_line(s)
+        end
+    end
+
+    # Backspace - also remove matching closing bracket/quote
+    bracket_insert_keymap['\b'] = (s::MIState, o...) -> begin
+        if is_region_active(s)
+            return edit_kill_region(s)
+        elseif isempty(s) || position(buffer(s)) == 0
+            # Handle transitioning to main mode
+            repl = Base.active_repl
+            mirepl = isdefined(repl, :mi) ? repl.mi : repl
+            main_mode = mirepl.interface.modes[1]
+            buf = copy(buffer(s))
+            transition(s, main_mode) do
+                state(s, main_mode).input_buffer = buf
+            end
+            return
+        end
+
+        buf = buffer(s)
+        left_brackets = ('(', '{', '[', '"', '\'', '`')
+        right_brackets = (')', '}', ']', '"', '\'', '`')
+
+        if !eof(buf) && position(buf) > 0
+            left_char = peek_char_left(buf)
+            i = findfirst(isequal(left_char), left_brackets)
+            if i !== nothing && peek(buf, Char) == right_brackets[i]
+                # Remove both the left and right bracket/quote
+                edit_delete(buf)
+                edit_backspace(buf)
+                return refresh_line(s)
+            end
+        end
+        return edit_backspace(s)
+    end
+end
+
 mutable struct HistoryPrompt <: TextInterface
     hp::HistoryProvider
     complete::CompletionProvider

stdlib/REPL/src/REPL.jl

@@ -1499,7 +1499,18 @@ function setup_interface(
                 end
                 Base.errormonitor(t_replswitch)
             else
-                edit_insert(s, ']')
+                # Use bracket insertion if enabled, otherwise just insert
+                if repl.options.auto_insert_closing_bracket
+                    buf = LineEdit.buffer(s)
+                    if !eof(buf) && LineEdit.peek(buf, Char) == ']'
+                        LineEdit.edit_move_right(buf)
+                    else
+                        edit_insert(buf, ']')
+                    end
+                    LineEdit.refresh_line(s)
+                else
+                    edit_insert(s, ']')
+                end
                 LineEdit.check_show_hint(s)
             end
         end,
@@ -1671,14 +1682,28 @@ function setup_interface(
 
     prefix_prompt, prefix_keymap = LineEdit.setup_prefix_keymap(hp, julia_prompt)
 
-    a = Dict{Any,Any}[skeymap, repl_keymap, prefix_keymap, LineEdit.history_keymap, LineEdit.default_keymap, LineEdit.escape_defaults]
+    # Build keymap list - add bracket insertion if enabled
+    base_keymaps = Dict{Any,Any}[skeymap, repl_keymap, prefix_keymap, LineEdit.history_keymap]
+    if repl.options.auto_insert_closing_bracket
+        push!(base_keymaps, LineEdit.bracket_insert_keymap)
+    end
+    push!(base_keymaps, LineEdit.default_keymap, LineEdit.escape_defaults)
+
+    a = base_keymaps
     prepend!(a, extra_repl_keymap)
 
     julia_prompt.keymap_dict = LineEdit.keymap(a)
 
     mk = mode_keymap(julia_prompt)
 
-    b = Dict{Any,Any}[skeymap, mk, prefix_keymap, LineEdit.history_keymap, LineEdit.default_keymap, LineEdit.escape_defaults]
+    # Build keymap list for other modes
+    mode_base_keymaps = Dict{Any,Any}[skeymap, mk, prefix_keymap, LineEdit.history_keymap]
+    if repl.options.auto_insert_closing_bracket
+        push!(mode_base_keymaps, LineEdit.bracket_insert_keymap)
+    end
+    push!(mode_base_keymaps, LineEdit.default_keymap, LineEdit.escape_defaults)
+
+    b = mode_base_keymaps
     prepend!(b, extra_repl_keymap)
 
     shell_mode.keymap_dict = help_mode.keymap_dict = dummy_pkg_mode.keymap_dict = LineEdit.keymap(b)

stdlib/REPL/src/options.jl

@@ -28,6 +28,7 @@ mutable struct Options
     # refresh after time delay
     auto_refresh_time_delay::Float64
     hint_tab_completes::Bool
+    auto_insert_closing_bracket::Bool # automatically insert closing brackets, quotes, etc.
     style_input::Bool # enable syntax highlighting for input
     # default IOContext settings at the REPL
     iocontext::Dict{Symbol,Any}
@@ -50,6 +51,7 @@ Options(;
         auto_indent_time_threshold = 0.005,
         auto_refresh_time_delay = 0.0, # this no longer seems beneficial
         hint_tab_completes = true,
+        auto_insert_closing_bracket = true,
         style_input = true,
         iocontext = Dict{Symbol,Any}()) =
             Options(hascolor, extra_keymap, tabwidth,
@@ -59,7 +61,7 @@ Options(;
                     backspace_align, backspace_adjust, confirm_exit,
                     auto_indent, auto_indent_tmp_off, auto_indent_bracketed_paste,
                     auto_indent_time_threshold, auto_refresh_time_delay,
-                    hint_tab_completes, style_input,
+                    hint_tab_completes, auto_insert_closing_bracket, style_input,
                     iocontext)
 
 # for use by REPLs not having an options field