Fix todo tag listing for empty filters

src/plugins/todo.rs

@@ -466,13 +466,24 @@ impl TodoPlugin {
             }
 
             // Otherwise, `todo tag [<filter>]` lists all known tags and lets you drill into `todo list`.
-            let mut filter = rest;
-            if let Some(stripped) = filter.strip_prefix("tag:") {
-                filter = stripped.trim();
-            }
-            if let Some(stripped) = filter.strip_prefix('#').or_else(|| filter.strip_prefix('@')) {
-                filter = stripped.trim();
-            }
+            let filter = if rest.is_empty() {
+                None
+            } else {
+                let mut filter = rest;
+                if let Some(stripped) = filter.strip_prefix("tag:") {
+                    filter = stripped.trim();
+                }
+                if let Some(stripped) =
+                    filter.strip_prefix('#').or_else(|| filter.strip_prefix('@'))
+                {
+                    filter = stripped.trim();
+                }
+                if filter.is_empty() {
+                    None
+                } else {
+                    Some(filter)
+                }
+            };
 
             let guard = match self.data.read() {
                 Ok(g) => g,
@@ -497,7 +508,7 @@ impl TodoPlugin {
                 .map(|(display, count)| (display, count))
                 .collect();
 
-            if !filter.is_empty() {
+            if let Some(filter) = filter {
                 tags.retain(|(tag, _)| self.matcher.fuzzy_match(tag, filter).is_some());
             }
 

tests/todo_plugin.rs

@@ -297,6 +297,26 @@ fn tag_command_filters_by_tag() {
     assert_eq!(results[0].label, "#urgent (1)");
     assert_eq!(results[0].action, "query:todo list #urgent");
 }
+
+#[test]
+fn tag_command_without_filter_lists_all_tags() {
+    let _lock = TEST_MUTEX.lock().unwrap();
+    let dir = tempdir().unwrap();
+    std::env::set_current_dir(dir.path()).unwrap();
+
+    append_todo(TODO_FILE, "alpha task", 1, &["alpha".into(), "beta".into()]).unwrap();
+    append_todo(TODO_FILE, "beta task", 1, &["beta".into()]).unwrap();
+    append_todo(TODO_FILE, "gamma task", 1, &["gamma".into(), "alpha".into()]).unwrap();
+
+    let plugin = TodoPlugin::default();
+    let results = plugin.search("todo tag");
+    let labels: Vec<&str> = results.iter().map(|action| action.label.as_str()).collect();
+
+    assert_eq!(
+        labels,
+        vec!["#alpha (2)", "#beta (2)", "#gamma (1)"]
+    );
+}
 #[test]
 fn search_view_opens_dialog() {
     let _lock = TEST_MUTEX.lock().unwrap();