fix: guess completion insertion range by back scanning for trigger chars or word breaks

closes #484

src/tui/editor.zig

@@ -4995,6 +4995,32 @@ pub const Editor = struct {
         _ = self.pop_tabstop();
     }
 
+    fn is_trigger_left(root: Buffer.Root, cursor: *const Cursor, metrics: Buffer.Metrics, triggers: []const TriggerSymbol) bool {
+        if (cursor.col == 0) return true;
+        var next = cursor.*;
+        next.move_left(root, metrics) catch return true;
+        const egc_left, _, _ = next.egc_at(root, metrics) catch return true;
+        switch (egc_left[0]) {
+            ' ', '\t' => return true,
+            else => |c| for (triggers) |t| if (c == t.char) return true,
+        }
+        return false;
+    }
+
+    pub fn guest_completion_range(self: *Self) Selection {
+        var cursel = self.get_primary().*;
+        var sel = Selection.from_cursor(&cursel.cursor);
+        if (cursel.cursor.col == 0) return sel;
+        const root = self.buf_root() catch return sel;
+
+        while (!is_trigger_left(root, &sel.begin, self.metrics, self.get_event_triggers(.insert).items))
+            move_cursor_left(root, &sel.begin, self.metrics) catch return sel;
+
+        if (tui.config().completion_insert_mode == .replace)
+            move_cursor_word_right(root, &sel.end, self.metrics) catch return sel;
+        return sel;
+    }
+
     fn replicate_selection(self: *Self, sel: Selection) void {
         if (sel.begin.row != sel.end.row) return;
         const primary = self.get_primary();

src/tui/mode/overlay/completion_dropdown.zig

@@ -4,6 +4,7 @@ const tp = @import("thespian");
 const root = @import("soft_root").root;
 const command = @import("command");
 const Buffer = @import("Buffer");
+const Selection = Buffer.Selection;
 const builtin = @import("builtin");
 const CompletionItemKind = @import("lsp_types").CompletionItemKind;
 
@@ -33,7 +34,7 @@ pub const ValueType = struct {
     editor: *ed.Editor = undefined,
     cursor: ed.Cursor = .{},
     view: ed.View = .{},
-    query: ?Buffer.Selection = null,
+    query: ?Selection = null,
     last_query: ?[]const u8 = null,
     commands: command.Collection(cmds) = undefined,
     data: []const u8 = &.{},
@@ -118,7 +119,7 @@ pub fn initial_query(self: *Type, allocator: std.mem.Allocator) error{ Stop, Out
 
 fn get_query_text_nostore(self: *Type, cursor: ed.Cursor, allocator: std.mem.Allocator) error{ Stop, OutOfMemory }![]const u8 {
     return if (self.value.query) |query| blk: {
-        const sel: Buffer.Selection = .{ .begin = query.begin, .end = cursor };
+        const sel: Selection = .{ .begin = query.begin, .end = cursor };
         break :blk try self.value.editor.get_selection(sel, allocator);
     } else allocator.dupe(u8, "");
 }
@@ -219,8 +220,8 @@ pub const Values = struct {
     label: []const u8,
     sort_text: []const u8,
     kind: CompletionItemKind,
-    insert: ?Buffer.Selection,
-    replace: ?Buffer.Selection,
+    insert: ?Selection,
+    replace: ?Selection,
     additionalTextEdits: []const u8,
     label_detail: []const u8,
     label_description: []const u8,
@@ -282,8 +283,8 @@ pub fn get_values(item_cbor: []const u8) Values {
     };
 }
 
-fn get_range(range_cbor: []const u8) ?Buffer.Selection {
-    var range: Buffer.Selection = .{};
+fn get_range(range_cbor: []const u8) ?Selection {
+    var range: Selection = .{};
     return if (cbor.match(range_cbor, tp.null_) catch false)
         null
     else if (cbor.match(range_cbor, .{
@@ -301,11 +302,11 @@ const TextEdit = struct { newText: []const u8 = &.{}, insert: ?Range = null, rep
 const Range = struct { start: Position, end: Position };
 const Position = struct { line: usize, character: usize };
 
-pub fn get_query_selection(editor: *ed.Editor, values: Values) ?Buffer.Selection {
+pub fn get_query_selection(editor: *ed.Editor, values: Values) ?Selection {
     return get_replacement_selection(editor, values.insert, values.replace, null);
 }
 
-fn get_replacement_selection(editor: *ed.Editor, insert_: ?Buffer.Selection, replace_: ?Buffer.Selection, query: ?Buffer.Selection) Buffer.Selection {
+fn get_replacement_selection(editor: *ed.Editor, insert_: ?Selection, replace_: ?Selection, query: ?Selection) Selection {
     const pos = switch (tui.config().completion_insert_mode) {
         .replace => replace_ orelse insert_,
         .insert => insert_ orelse replace_,
@@ -313,19 +314,8 @@ fn get_replacement_selection(editor: *ed.Editor, insert_: ?Buffer.Selection, rep
 
     var sel = if (pos) |p|
         p.from_pos(editor.buf_root() catch return ed.Selection.from_cursor(&editor.get_primary().cursor), editor.metrics)
-    else blk: {
-        if (query) |sel| break :blk sel;
-        var cursel = editor.get_primary().*;
-        var sel = ed.Selection.from_cursor(&cursel.cursor);
-        if (cursel.cursor.col == 0) break :blk sel;
-        const root_ = editor.buf_root() catch break :blk sel;
-        ed.Editor.move_cursor_word_left(root_, &sel.begin, editor.metrics) catch break :blk sel;
-        if (tui.config().completion_insert_mode == .replace) {
-            sel.end = sel.begin;
-            ed.Editor.move_cursor_word_right(root_, &sel.end, editor.metrics) catch break :blk sel;
-        }
-        break :blk sel;
-    };
+    else
+        query orelse editor.guest_completion_range();
     sel.normalize();
     const cursor = editor.get_primary().cursor;
     return switch (tui.config().completion_insert_mode) {
@@ -334,7 +324,7 @@ fn get_replacement_selection(editor: *ed.Editor, insert_: ?Buffer.Selection, rep
     };
 }
 
-fn get_insert_selection(editor: *ed.Editor, values: Values, query: ?Buffer.Selection) Buffer.Selection {
+fn get_insert_selection(editor: *ed.Editor, values: Values, query: ?Selection) Selection {
     return get_replacement_selection(editor, values.insert, values.replace, query);
 }