filter: Fix unparse to round-trip Unicode whitespace operands.

Previously [{operator: "topic", operand: "one\xa0two"}] would be
unparsed to "topic:one\xa0two" which parses as [{operator: "topic",
operand: "one"}, {operator: "search", operand: "two"}], leading to
exceptions in the search pill system.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

web/src/filter.ts

@@ -448,20 +448,19 @@ export class Filter {
        This is just for the search bar, not for saving the
        narrow in the URL fragment.  There we do use full
        URI encoding to avoid problematic characters. */
-    static encodeOperand(operand: string): string {
-        return operand
-            .replaceAll("%", "%25")
-            .replaceAll("+", "%2B")
-            .replaceAll(" ", "+")
-            .replaceAll('"', "%22");
+    static encodeOperand(operand: string, operator: string): string {
+        if (USER_OPERATORS.has(operator)) {
+            return operand.replaceAll(/[\s"%]/g, (c) => encodeURIComponent(c));
+        }
+        return operand.replaceAll(/[\s"%+]/g, (c) => (c === " " ? "+" : encodeURIComponent(c)));
     }
 
     static decodeOperand(encoded: string, operator: string): string {
-        encoded = encoded.replaceAll('"', "");
+        encoded = encoded.trim().replaceAll('"', "");
         if (!USER_OPERATORS.has(operator)) {
             encoded = encoded.replaceAll("+", " ");
         }
-        return util.robust_url_decode(encoded).trim();
+        return util.robust_url_decode(encoded);
     }
 
     // Parse a string into a list of terms (see below).
@@ -618,7 +617,9 @@ export class Filter {
                 return term.operand;
             }
             const operator = Filter.canonicalize_operator(term.operator);
-            return sign + operator + ":" + Filter.encodeOperand(term.operand.toString());
+            return (
+                sign + operator + ":" + Filter.encodeOperand(term.operand.toString(), term.operator)
+            );
         });
         return term_strings.join(" ");
     }

web/tests/filter.test.js

@@ -1461,6 +1461,14 @@ test("unparse", () => {
     ];
     string = `channel:${foo_stream_id} topic:Bar`;
     assert.deepEqual(Filter.unparse(terms), string);
+
+    terms = [
+        {operator: "dm", operand: '\t "%+.\u00A0'},
+        {operator: "topic", operand: '\t "%+.\u00A0'},
+    ];
+    string = "dm:%09%20%22%25+.%C2%A0 topic:%09+%22%25%2B.%C2%A0";
+    assert.equal(Filter.unparse(terms), string);
+    assert_same_terms(Filter.parse(string), terms);
 });
 
 test("describe", ({mock_template}) => {