Add command to add word boundaries to search (#4322)

* Add command to add word boundaries to search

* Calculate string capacity before building

Author: mitsuhiko

helix-term/src/commands.rs

@@ -250,6 +250,7 @@ impl MappableCommand {
         extend_search_next, "Add next search match to selection",
         extend_search_prev, "Add previous search match to selection",
         search_selection, "Use current selection as search pattern",
+        make_search_word_bounded, "Modify current search to make it word bounded",
         global_search, "Global search in workspace folder",
         extend_line, "Select current line, if already selected, extend to another line based on the anchor",
         extend_line_below, "Select current line, if already selected, extend to next line",
@@ -1809,6 +1810,35 @@ fn search_selection(cx: &mut Context) {
     cx.editor.set_status(msg);
 }
 
+fn make_search_word_bounded(cx: &mut Context) {
+    let regex = match cx.editor.registers.last('/') {
+        Some(regex) => regex,
+        None => return,
+    };
+    let start_anchored = regex.starts_with("\\b");
+    let end_anchored = regex.ends_with("\\b");
+
+    if start_anchored && end_anchored {
+        return;
+    }
+
+    let mut new_regex = String::with_capacity(
+        regex.len() + if start_anchored { 0 } else { 2 } + if end_anchored { 0 } else { 2 },
+    );
+
+    if !start_anchored {
+        new_regex.push_str("\\b");
+    }
+    new_regex.push_str(regex);
+    if !end_anchored {
+        new_regex.push_str("\\b");
+    }
+
+    let msg = format!("register '{}' set to '{}'", '/', &new_regex);
+    cx.editor.registers.get_mut('/').push(new_regex);
+    cx.editor.set_status(msg);
+}
+
 fn global_search(cx: &mut Context) {
     #[derive(Debug)]
     struct FileResult {