Handle newlines in user pills (#11166)

* Handle newlines in user pills

Fixes: vector-im/element-web#10994

* Fix typo in comment

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* Refactor link generation for better readability

* Use `<br>` instead of `<br/>`

* Fix copy/paste error

---------

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

src/Markdown.ts

@@ -22,7 +22,7 @@ import { logger } from "matrix-js-sdk/src/logger";
 
 import { linkify } from "./linkify-matrix";
 
-const ALLOWED_HTML_TAGS = ["sub", "sup", "del", "u"];
+const ALLOWED_HTML_TAGS = ["sub", "sup", "del", "u", "br", "br/"];
 
 // These types of node are definitely text
 const TEXT_NODES = ["text", "softbreak", "linebreak", "paragraph", "document"];
@@ -36,8 +36,8 @@ function isAllowedHtmlTag(node: commonmark.Node): boolean {
         return true;
     }
 
-    // Regex won't work for tags with attrs, but we only
-    // allow <del> anyway.
+    // Regex won't work for tags with attrs, but the tags we allow
+    // shouldn't really have any anyway.
     const matches = /^<\/?(.*)>$/.exec(node.literal);
     if (matches && matches.length == 2) {
         const tag = matches[1];

src/editor/serialize.ts

@@ -36,20 +36,20 @@ export function mdSerialize(model: EditorModel): string {
             case Type.PillCandidate:
             case Type.AtRoomPill:
                 return html + part.text;
-            case Type.RoomPill:
+            case Type.RoomPill: {
+                const url = makeGenericPermalink(part.resourceId);
+                // Escape square brackets and backslashes
                 // Here we use the resourceId for compatibility with non-rich text clients
                 // See https://github.com/vector-im/element-web/issues/16660
-                return (
-                    html +
-                    `[${part.resourceId.replace(/[[\\\]]/g, (c) => "\\" + c)}](${makeGenericPermalink(
-                        part.resourceId,
-                    )})`
-                );
-            case Type.UserPill:
-                return (
-                    html +
-                    `[${part.text.replace(/[[\\\]]/g, (c) => "\\" + c)}](${makeGenericPermalink(part.resourceId)})`
-                );
+                const title = part.resourceId.replace(/[[\\\]]/g, (c) => "\\" + c);
+                return html + `[${title}](${url})`;
+            }
+            case Type.UserPill: {
+                const url = makeGenericPermalink(part.resourceId);
+                // Escape square brackets and backslashes; convert newlines to HTML
+                const title = part.text.replace(/[[\\\]]/g, (c) => "\\" + c).replace(/\n/g, "<br>");
+                return html + `[${title}](${url})`;
+            }
         }
     }, "");
 }

test/editor/deserialize-test.ts

@@ -183,6 +183,14 @@ describe("editor/deserialize", function () {
             expect(parts[1]).toStrictEqual({ type: "user-pill", text: "Alice]", resourceId: "@alice:hs.tld" });
             expect(parts[2]).toStrictEqual({ type: "plain", text: "!" });
         });
+        it("user pill with displayname containing linebreak", function () {
+            const html = 'Hi <a href="https://matrix.to/#/@alice:hs.tld">Alice<br>123</a>!';
+            const parts = normalize(parseEvent(htmlMessage(html), createPartCreator()));
+            expect(parts.length).toBe(3);
+            expect(parts[0]).toStrictEqual({ type: "plain", text: "Hi " });
+            expect(parts[1]).toStrictEqual({ type: "user-pill", text: "Alice123", resourceId: "@alice:hs.tld" });
+            expect(parts[2]).toStrictEqual({ type: "plain", text: "!" });
+        });
         it("room pill", function () {
             const html = 'Try <a href="https://matrix.to/#/#room:hs.tld">#room:hs.tld</a>?';
             const parts = normalize(parseEvent(htmlMessage(html), createPartCreator()));

test/editor/serialize-test.ts

@@ -63,6 +63,12 @@ describe("editor/serialize", function () {
             const html = htmlSerializeIfNeeded(model, {});
             expect(html).toBe('<a href="https://matrix.to/#/@user:server">Displayname]</a>');
         });
+        it("displaynames containing a newline work", function () {
+            const pc = createPartCreator();
+            const model = new EditorModel([pc.userPill("Display\nname", "@user:server")], pc);
+            const html = htmlSerializeIfNeeded(model, {});
+            expect(html).toBe('<a href="https://matrix.to/#/@user:server">Display<br>name</a>');
+        });
         it("escaped markdown should not retain backslashes", function () {
             const pc = createPartCreator();
             const model = new EditorModel([pc.plain("\\*hello\\* world")], pc);
@@ -96,7 +102,6 @@ describe("editor/serialize", function () {
             const html = htmlSerializeIfNeeded(model, { useMarkdown: false });
             expect(html).toBe("\\*hello\\* world &lt; hey world!");
         });
-
         it("plaintext remains plaintext even when forcing html", function () {
             const pc = createPartCreator();
             const model = new EditorModel([pc.plain("hello world")], pc);