subs: Move active_stream function to hash_util.

This function better belongs in hash_util since it relies on
the current window hash.

frontend_tests/node_tests/hash_util.js

@@ -119,6 +119,15 @@ run_test("build_reload_url", () => {
     assert.equal(hash_util.build_reload_url(), "+oldhash=");
 });
 
+run_test("test_active_stream", () => {
+    location.hash = "#streams/1/announce";
+    assert.equal(hash_util.active_stream().id, 1);
+    assert.equal(hash_util.active_stream().name, "announce");
+
+    location.hash = "#test/narrow";
+    assert.equal(hash_util.active_stream(), undefined);
+});
+
 run_test("test_parse_narrow", () => {
     assert.deepEqual(hash_util.parse_narrow(["narrow", "stream", "99-frontend"]), [
         {negated: false, operator: "stream", operand: "frontend"},

frontend_tests/node_tests/stream_edit.js

@@ -21,6 +21,7 @@ mock_esm("../../static/js/browser_history", {update: noop});
 mock_esm("../../static/js/hash_util", {
     stream_edit_uri: noop,
     by_stream_uri: noop,
+    active_stream: noop,
 });
 mock_esm("../../static/js/list_widget", {
     create: () => ({init: noop}),

static/js/hash_util.js

@@ -249,3 +249,20 @@ export function is_overlay_hash(hash) {
 
     return overlay_list.includes(main_hash);
 }
+
+// this finds the stream that is actively open in the settings and focused in
+// the left side.
+export function active_stream() {
+    const hash_components = window.location.hash.slice(1).split(/\//);
+
+    // if the string casted to a number is valid, and another component
+    // after exists then it's a stream name/id pair.
+    if (typeof Number.parseFloat(hash_components[1]) === "number" && hash_components[2]) {
+        return {
+            id: Number.parseFloat(hash_components[1]),
+            name: hash_components[2],
+        };
+    }
+
+    return undefined;
+}

static/js/stream_edit.js

@@ -78,7 +78,7 @@ export function is_sub_settings_active(sub) {
     // currently being viewed/edited in the stream edit UI.  This is
     // used to determine whether we need to rerender the stream edit
     // UI when a sub object is modified by an event.
-    const active_stream = subs.active_stream();
+    const active_stream = hash_util.active_stream();
     if (active_stream !== undefined && active_stream.id === sub.stream_id) {
         return true;
     }

static/js/subs.js

@@ -145,23 +145,6 @@ function should_list_all_streams() {
     return !page_params.realm_is_zephyr_mirror_realm;
 }
 
-// this finds the stream that is actively open in the settings and focused in
-// the left side.
-export function active_stream() {
-    const hash_components = window.location.hash.slice(1).split(/\//);
-
-    // if the string casted to a number is valid, and another component
-    // after exists then it's a stream name/id pair.
-    if (typeof Number.parseFloat(hash_components[1]) === "number" && hash_components[2]) {
-        return {
-            id: Number.parseFloat(hash_components[1]),
-            name: hash_components[2],
-        };
-    }
-
-    return undefined;
-}
-
 export function set_muted(sub, is_muted, status_element) {
     stream_muting.update_is_muted(sub, is_muted);
     stream_edit.set_stream_property(sub, "is_muted", sub.is_muted, status_element);