fix(core): match multi-variable URI templates like {a,b} (#2166)

`UriTemplate.expand` already joins multi-name expansions with commas,
but `match` only emitted one regex capture per part and assigned the
whole captured run to the first name. Anything past the first variable
silently never matched and resources registered against templates like
`data://users/{userId,format}` were unreachable.

Emit one capture per name with literal commas between them in
`partToRegExp`, mirroring what `expandPart` produces, so round
tripping through expand and match recovers the original variables.
Path / label / fragment operators get their existing literal prefix
on the first capture; the bare and reserved cases just sit at the
current position.

Author: NishchayMahor

packages/core/src/shared/uriTemplate.ts

@@ -222,6 +222,41 @@ export class UriTemplate {
             return patterns;
         }
 
+        // Multi-variable expressions like `{a,b}` or `{/a,b}` expand each value
+        // and join them with commas (see `expandPart`). Mirror that on the way
+        // back by emitting one capture per name with literal commas between
+        // them. Without this, only the first name was assigned and the rest of
+        // the path silently never matched (#2166).
+        if (part.names.length > 1) {
+            let firstPrefix: string;
+            switch (part.operator) {
+                case '/': {
+                    firstPrefix = '/';
+                    break;
+                }
+                case '.': {
+                    firstPrefix = String.raw`\.`;
+                    break;
+                }
+                case '#': {
+                    firstPrefix = '#';
+                    break;
+                }
+                default: {
+                    firstPrefix = '';
+                }
+            }
+            for (let i = 0; i < part.names.length; i++) {
+                const name = part.names[i]!;
+                const prefix = i === 0 ? firstPrefix : ',';
+                patterns.push({
+                    pattern: prefix + '([^/,]+)',
+                    name
+                });
+            }
+            return patterns;
+        }
+
         let pattern: string;
         const name = part.name;
 

packages/core/test/shared/uriTemplate.test.ts

@@ -98,6 +98,25 @@ describe('UriTemplate', () => {
             expect(match).toEqual({ username: 'fred', postId: '123' });
         });
 
+        it('should match a comma-separated multi-variable expression (#2166)', () => {
+            const template = new UriTemplate('/users/{userId,format}');
+            const match = template.match('/users/42,json');
+            expect(match).toEqual({ userId: '42', format: 'json' });
+        });
+
+        it('should round-trip expand and match for a multi-variable expression (#2166)', () => {
+            const template = new UriTemplate('data://users/{userId,format}');
+            const expanded = template.expand({ userId: '42', format: 'json' });
+            expect(expanded).toBe('data://users/42,json');
+            expect(template.match(expanded)).toEqual({ userId: '42', format: 'json' });
+        });
+
+        it('should match a multi-variable expression with the path operator (#2166)', () => {
+            const template = new UriTemplate('{/userId,format}');
+            const match = template.match('/42,json');
+            expect(match).toEqual({ userId: '42', format: 'json' });
+        });
+
         it('should return null for non-matching URIs', () => {
             const template = new UriTemplate('/users/{username}');
             const match = template.match('/posts/123');