[FIX] mail: fix suggestion hook char deletion

Before this commit, the suggestion list would not work when
a string with no match was entered then modified.

Steps to reproduce:
- Open a channel
- Type `/hee` (this string matches no suggestion)
- Delete one of the `e` in order to get `/he`
- This string should match the `/help` suggestion but nothing
is shown.

There is several issues here:
- The suggestion hook is based on the composer selection but
the `selectionChange` event is not triggered when deleting text
from the textarea which leads to incorrect selection.
- The search is cleared in the `suggestionHook` when nothing is
found which leads to incorrect delimiter position after a deletion.

This commit fixes both issues.

closes odoo/odoo#127997

X-original-commit: b8bf65478cad558e02a5902886b3e4272483944e
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/core/common/suggestion_hook.js

@@ -136,7 +136,7 @@ export function useSuggestion() {
             );
             const { type, mainSuggestions, extraSuggestions = [] } = suggestions;
             if (!mainSuggestions.length && !extraSuggestions.length) {
-                self.clearSearch();
+                self.state.items = undefined;
                 return;
             }
             // arbitrary limit to avoid displaying too many elements at once

addons/mail/static/src/utils/common/hooks.js

@@ -288,9 +288,11 @@ export function useSelection({ refName, model, preserveOnClickAwayPredicate = ()
     });
     onMounted(() => {
         document.addEventListener("selectionchange", onSelectionChange);
+        document.addEventListener("input", onSelectionChange);
     });
     onWillUnmount(() => {
         document.removeEventListener("selectionchange", onSelectionChange);
+        document.removeEventListener("input", onSelectionChange);
     });
     return {
         restore() {

addons/mail/static/tests/discuss/core/suggestion_tests.js

@@ -2,7 +2,13 @@
 
 import { Composer } from "@mail/core/common/composer";
 import { Command } from "@mail/../tests/helpers/command";
-import { click, insertText, start, startServer } from "@mail/../tests/helpers/test_utils";
+import {
+    afterNextRender,
+    click,
+    insertText,
+    start,
+    startServer,
+} from "@mail/../tests/helpers/test_utils";
 
 import { patchWithCleanup } from "@web/../tests/helpers/utils";
 
@@ -124,3 +130,22 @@ QUnit.test("Sort partner suggestions by recent chats", async (assert) => {
     assert.strictEqual($(".o-mail-Composer-suggestion").eq(1).text(), "User 1");
     assert.strictEqual($(".o-mail-Composer-suggestion").eq(2).text(), "User 3");
 });
+
+QUnit.test("suggestion are shown after deleting a character", async (assert) => {
+    const pyEnv = await startServer();
+    const channelId = pyEnv["discuss.channel"].create({
+        name: "General",
+        channel_type: "channel",
+    });
+    const { openDiscuss } = await start();
+    await openDiscuss(channelId);
+    await insertText(".o-mail-Composer-input", "/");
+    await insertText(".o-mail-Composer-input", "hee");
+    assert.containsNone($, ".o-mail-Composer-suggestion:contains(help)");
+    // Simulate pressing backspace
+    await afterNextRender(() => {
+        const textarea = document.querySelector(".o-mail-Composer-input");
+        textarea.value = textarea.value.slice(0, -1);
+    });
+    assert.containsOnce($, ".o-mail-Composer-suggestion:contains(help)");
+});