Byron94odhiambo opened a new pull request, #61665:
URL: https://github.com/apache/airflow/pull/61665
<h2>Summary</h2>
<p>This PR adds support for cascading (dependent) dropdown parameters in the
Trigger DAG form. When a user selects a value in a parent dropdown, child
dropdowns automatically filter to show only the relevant options.</p>
<h2>Usage</h2>
<pre><code class="language-python">from airflow.sdk.definitions.param import
Param
with DAG(
"my_dag",
params={
"country": Param("Kenya", type="string", enum=["Kenya", "Ethiopia",
"Tanzania"]),
"region": Param(
"Nandi County",
type="string",
depends_on="country",
options_map={
"Kenya": ["Nandi County", "Nyandarua", "Nakuru", "Kiambu"],
"Ethiopia": ["Jimma", "Arsi", "Bale", "Sidama"],
"Tanzania": ["Arusha", "Dodoma", "Mwanza", "Tanga"],
},
),
"city": Param(
"Kapsabet",
type="string",
depends_on="region",
options_map={
"Nandi County": ["Kapsabet", "Nandi Hills", "Mosoriot"],
"Nyandarua": ["Ol Kalou", "Engineer", "Ndaragwa"],
# ... more mappings
},
),
},
) as dag:
...
</code></pre>
<h2>How It Works</h2>
<ul>
<li><strong><code>depends_on</code></strong>: Names the parent parameter
whose value controls this dropdown's options.</li>
<li><strong><code>options_map</code></strong>: A dict mapping each parent
value to the list of allowed child options.</li>
<li>When the parent value changes, the child dropdown filters to show only
matching options and auto-resets if the current selection is no longer
valid.</li>
<li>Multi-level cascading is supported (e.g., country → region → city).</li>
</ul>
<h2>Changes</h2>
Layer | File | What
-- | -- | --
SDK | task-sdk/src/airflow/sdk/definitions/param.py | Add depends_on +
options_map attrs to Param, auto-populate enum from options_map, preserve
through copy/dump/serialize/deserialize
Serialization | airflow-core/src/airflow/serialization/serialized_objects.py
| Persist depends_on/options_map through DB serialization round-trip
Serialization | airflow-core/src/airflow/serialization/definitions/param.py
| Add SerializedParam support for cascading fields
Frontend |
airflow-core/src/airflow/ui/src/components/FlexibleForm/FieldDropdown.tsx |
Compute effectiveEnum from parent value, auto-reset invalid child values
Frontend | airflow-core/src/airflow/ui/src/queries/useDagParams.ts | Add
depends_on/options_map to ParamSpec type
Frontend | airflow-core/src/airflow/ui/src/queries/useParamStore.ts |
Preserve cascading fields through param store rebuilds
Example |
airflow-core/src/airflow/example_dags/example_params_cascading_dropdown.py |
3-level cascade demo DAG (country → region → city)
Tests | task-sdk/tests/test_param_cascading.py | 16 unit tests covering all
cascading scenarios
<h2>Testing</h2>
<h3>Backend</h3>
<pre><code class="language-bash">python -m pytest
task-sdk/tests/test_param_cascading.py -v --noconftest -o "asyncio_mode=auto"
-o "addopts="
# 16/16 PASSED ✅
</code></pre>
<h3>Frontend</h3>
<ol>
<li>Start Airflow: <code>airflow standalone</code></li>
<li>Open http://localhost:8080</li>
<li>Find <strong>"Cascading Params Example"</strong> DAG</li>
<li>Click <strong>Trigger</strong> to open the parameter form</li>
<li>Change <strong>Country</strong> → Region dropdown filters to matching
regions</li>
<li>Change <strong>Region</strong> → City dropdown filters to matching
cities</li>
</ol>
<h3>Validation</h3>
<ul>
<li><code>depends_on</code> without <code>options_map</code> raises
<code>TypeError</code></li>
<li><code>options_map</code> without <code>depends_on</code> raises
<code>TypeError</code></li>
<li><code>options_map</code> values must be lists</li>
<li>Non-cascading params are completely unaffected</li>
<li>Cascading metadata survives serialize → DB → deserialize → API
round-trip</li>
</ul></body></html>
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