Show rendered templates from the CLI

airflow/bin/cli.py

@@ -3,6 +3,7 @@
 import logging
 import os
 import subprocess
+import textwrap
 from datetime import datetime
 
 from builtins import input
@@ -266,7 +267,6 @@ def list_tasks(args):
 
 
 def test(args):
-
     args.execution_date = dateutil.parser.parse(args.execution_date)
     dagbag = DagBag(process_subdir(args.subdir))
     if args.dag_id not in dagbag.dags:
@@ -281,6 +281,24 @@ def test(args):
         ti.run(force=True, ignore_dependencies=True, test_mode=True)
 
 
+def render(args):
+    args.execution_date = dateutil.parser.parse(args.execution_date)
+    dagbag = DagBag(process_subdir(args.subdir))
+    if args.dag_id not in dagbag.dags:
+        raise AirflowException('dag_id could not be found')
+    dag = dagbag.dags[args.dag_id]
+    task = dag.get_task(task_id=args.task_id)
+    ti = TaskInstance(task, args.execution_date)
+    ti.render_templates()
+    for attr in task.__class__.template_fields:
+        print(textwrap.dedent("""\
+        # ----------------------------------------------------------
+        # property: {}
+        # ----------------------------------------------------------
+        {}
+        """.format(attr, getattr(task, attr))))
+
+
 def clear(args):
     logging.basicConfig(
         level=settings.LOGGING_LEVEL,
@@ -703,4 +721,15 @@ def get_parser():
         nargs='?', default=configuration.get('kerberos', 'principal'))
     parser_kerberos.set_defaults(func=kerberos)
 
+    ht = "Render a task instance's template(s)"
+    parser_render = subparsers.add_parser('render', help=ht)
+    parser_render.add_argument("dag_id", help="The id of the dag to check")
+    parser_render.add_argument("task_id", help="The task_id to check")
+    parser_render.add_argument(
+        "execution_date", help="The execution date to check")
+    parser_render.add_argument(
+        "-sd", "--subdir", help=subdir_help,
+        default=DAGS_FOLDER)
+    parser_render.set_defaults(func=render)
+
     return parser

airflow/models.py

@@ -1196,7 +1196,7 @@ def render_templates(self):
         for attr in task.__class__.template_fields:
             content = getattr(task, attr)
             if content:
-                rendered_content = self.task.render_template(content, jinja_context)
+                rendered_content = rt(content, jinja_context)
                 setattr(task, attr, rendered_content)
 
     def email_alert(self, exception, is_retry=False):