Test modification of a task by an on-add hook (test case for #3416) (#3443)

* Add test case to cover https://github.com/GothenburgBitFactory/taskwarrior/issues/3416

* Add (builtin) on-add-modify test hook and use it

* TDB2::add() move hook invocation before save (#3416)

test/hooks.on-add.test.py

@@ -58,6 +58,23 @@ class TestHooksOnAdd(TestCase):
         code, out, err = self.t("1 info")
         self.assertIn("Description   foo", out)
 
+    def test_onadd_builtin_accept_modify(self):
+        """on-add-accept-modify - a well-behaved, successful, on-add hook, that modifies the added task."""
+        hookname = 'on-add-modify'
+        self.t.hooks.add_default(hookname, log=True)
+
+        code, out, err = self.t("add teh foo")
+
+        hook = self.t.hooks[hookname]
+        hook.assertTriggeredCount(1)
+        hook.assertExitcode(0)
+
+        logs = hook.get_logs()
+        self.assertEqual(logs["output"]["msgs"][0], "FEEDBACK")
+
+        code, out, err = self.t("1 info")
+        self.assertIn("Description   the foo", out)
+
     def test_onadd_builtin_reject(self):
         """on-add-reject - a well-behaved, failing, on-add hook."""
         hookname = 'on-add-reject'

test/test_hooks/on-add-modify

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+# Input:
+# - Line of JSON for proposed new task.
+read new_task
+
+if (echo $new_task | grep -qE '[tT]eh');
+then
+  new_task=$(echo $new_task | sed -r 's/([tT])eh/\1he/g')
+fi
+
+# Output:
+# - JSON, modified
+# - Optional feedback/error.
+echo $new_task
+echo 'FEEDBACK'
+
+# Status:
+# - 0:     JSON accepted, non-JSON is feedback.
+# - non-0: JSON ignored, non-JSON is error.
+exit 0