Merge pull request #32135 from overleaf/mg-comment-empty-select

Allow adding comments on empty selection

GitOrigin-RevId: 14e742bb563fab99624be860691f1a9d2dabc00e

services/web/frontend/js/features/source-editor/utils/is-cursor-on-empty-line.ts

@@ -0,0 +1,18 @@
+import { EditorState } from '@codemirror/state'
+
+/**
+ * Returns true when the cursor is on an empty line with no active selection.
+ *
+ * Used to disable the "Add comment" action — there is nothing to anchor a
+ * comment to on a blank line.
+ */
+export function isCursorOnEmptyLine(state: EditorState): boolean {
+  const { main } = state.selection
+
+  if (!main.empty) {
+    return false
+  }
+
+  const line = state.doc.lineAt(main.head)
+  return line.text.trim().length === 0
+}

services/web/frontend/js/features/source-editor/utils/select-highlighted-or-nearest-token.ts

@@ -0,0 +1,68 @@
+import { EditorState } from '@codemirror/state'
+import { isCursorOnEmptyLine } from './is-cursor-on-empty-line'
+
+/**
+ * Returns the current highlighted range, or the nearest non-whitespace token
+ * to the cursor when there is no active selection.
+ *
+ * "Token" here means any contiguous run of non-whitespace characters (`/\S+/`),
+ * not necessarily an alphanumeric word. When two tokens are equidistant the
+ * earlier one (closer to document start) wins.
+ *
+ * Only searches the current line.
+ *
+ * Only called on user-initiated actions (e.g. "Add comment"), not on every render.
+ * Returns null when the cursor is on an empty/whitespace-only line.
+ */
+export function selectHighlightedOrNearestToken(
+  state: EditorState
+): { from: number; to: number } | null {
+  if (isCursorOnEmptyLine(state)) {
+    return null
+  }
+
+  const { main } = state.selection
+
+  if (!main.empty) {
+    return { from: main.from, to: main.to }
+  }
+
+  const pos = main.head
+  const line = state.doc.lineAt(pos)
+
+  let bestFrom = 0
+  let bestTo = 0
+  let bestDist = Infinity
+
+  for (const match of line.text.matchAll(/\S+/g)) {
+    const from = line.from + match.index!
+    const to = from + match[0].length
+
+    let dist = 0
+    if (pos < from) {
+      dist = from - pos
+    } else if (pos > to) {
+      dist = pos - to
+    }
+
+    if (dist === 0) {
+      return { from, to }
+    }
+
+    if (dist < bestDist) {
+      bestFrom = from
+      bestTo = to
+      bestDist = dist
+    }
+
+    // Past the cursor — no closer match possible on this line
+    if (from > pos) {
+      break
+    }
+  }
+
+  if (bestDist < Infinity) {
+    return { from: bestFrom, to: bestTo }
+  }
+  return null
+}