Fix 1430: empty tasks names display list (#1431)

Co-authored-by: ikappaki <ikappaki@users.noreply.github.com>

CHANGELOG.md

@@ -7,6 +7,10 @@ A preview of the next release can be installed from
 
 [Babashka](https://github.com/babashka/babashka): Native, fast starting Clojure interpreter for scripting
 
+## Unreleased
+
+- [#1430](https://github.com/babashka/babashka/issues/1430): Fix issue with `bb tasks` throwing on empty display tasks list. 
+
 ## 1.0.166 (2022-11-24)
 
 See the [Testing babashka scripts](https://blog.michielborkent.nl/babashka-test-runner.html) blog post for how to run tests with this release.

src/babashka/impl/tasks.clj

@@ -429,15 +429,22 @@
           (iterate zip/right loc))))
 
 (defn list-tasks
+  "Prints out the task names found in BB-EDN in the original order
+  alongside their documentation as retrieved with SCI-CTX.
+
+  For a task to be listed
+  - its name has to be a symbol but should not start with `-`, and
+  - should not be `:private`."
   [sci-ctx]
-  (let [tasks (:tasks @bb-edn)]
-    (if (seq tasks)
-      (let [raw-edn (:raw @bb-edn)
-            names (key-order raw-edn)
-            names (map str names)
-            names (remove #(str/starts-with? % "-") names)
-            names (remove #(:private (get tasks (symbol %))) names)
-            longest (apply max (map count names))
+  (let [tasks (:tasks @bb-edn)
+        raw-edn (:raw @bb-edn)
+        names (when (seq tasks)
+                (->> (key-order raw-edn)
+                     (map str)
+                     (remove #(str/starts-with? % "-"))
+                     (remove #(:private (get tasks (symbol %))))))]
+    (if (seq names)
+      (let [longest (apply max (map count names))
             fmt (str "%1$-" longest "s")]
         (println "The following tasks are available:")
         (println)

test/babashka/bb_edn_test.clj

@@ -307,6 +307,25 @@
   (test-utils/with-config {}
     (let [res (test-utils/bb nil "tasks")]
       (is (str/includes? res "No tasks found."))))
+  (test-utils/with-config '{:tasks {:x 1}}
+    (let [res (test-utils/bb nil "tasks")]
+      (is (str/includes? res "No tasks found."))))
+  (test-utils/with-config '{:tasks {-xyz 5}}
+    (let [res (test-utils/bb nil "tasks")]
+      (is (str/includes? res "No tasks found."))))
+  (test-utils/with-config '{:tasks {xyz {:private true}}}
+    (let [res (test-utils/bb nil "tasks")]
+      (is (str/includes? res "No tasks found."))))
+  (test-utils/with-config '{:tasks {abc 1 xyz 2}}
+    (let [res (test-utils/bb nil "tasks")]
+      (is (= "The following tasks are available:\n\nabc\nxyz\n" res))))
+  (test-utils/with-config '{:tasks {abc 1  xyz {:doc "some text" :tasks 5}
+                                    -xyz 3 qrs {:private true}}}
+    (let [res (test-utils/bb nil "tasks")]
+      (is (= "The following tasks are available:\n\nabc\nxyz some text\n" res))))
+  (test-utils/with-config '{:tasks {xyz 1 abc 2}}
+    (let [res (test-utils/bb nil "tasks")]
+      (is (= "The following tasks are available:\n\nxyz\nabc\n" res))))
   (test-utils/with-config "{:paths [\"test-resources/task_scripts\"]
                             :tasks {:requires ([tasks :as t])
                                     task1