Add new resolvers oc.dict.keys and oc.dict.values

Fixes omry#643

docs/source/usage.rst

@@ -466,6 +466,34 @@ This can be useful for instance to parse environment variables:
     type: int, value: 3308
 
 
+Extracting lists of keys / values from a dictionary
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Some config options that are stored as a ``DictConfig`` may sometimes be easier to manipulate as lists,
+when we care only about the keys or the associated values.
+
+The resolvers ``oc.dict.keys`` and ``oc.dict.values`` simplify such operations by extracting respectively
+the list of keys and values from ``dict``-like objects like ``DictConfig``:
+
+.. doctest::
+
+    >>> cfg = OmegaConf.create(
+    ...     {
+    ...         "machines": {
+    ...             "node007": "10.0.0.7",
+    ...             "node012": "10.0.0.3",
+    ...             "node075": "10.0.1.8",
+    ...         },
+    ...         "nodes": "${oc.dict.keys:${machines}}",
+    ...         "ips": "${oc.dict.values:${machines}}",
+    ...     }
+    ... )
+    >>> show(cfg.nodes)
+    type: ListConfig, value: ['node007', 'node012', 'node075']
+    >>> show(cfg.ips)
+    type: ListConfig, value: ['10.0.0.7', '10.0.0.3', '10.0.1.8']
+
+
 Custom interpolations
 ^^^^^^^^^^^^^^^^^^^^^
 

news/643.feature

@@ -0,0 +1,2 @@
+New resolvers `oc.dict.keys` and `oc.dict.values` allow extracting the lists of keys and values of a DictConfig
+

omegaconf/built_in_resolvers.py

@@ -1,6 +1,6 @@
 import os
 import warnings
-from typing import Any, Optional
+from typing import Any, Dict, List, Optional
 
 from ._utils import _DEFAULT_MARKER_, _get_value, decode_primitive
 from .base import Container
@@ -28,6 +28,14 @@ def decode(expr: Optional[str], _parent_: Container) -> Any:
     return _get_value(val)
 
 
+def dict_keys(in_dict: Dict[Any, Any]) -> List[Any]:
+    return list(in_dict.keys())
+
+
+def dict_values(in_dict: Dict[Any, Any]) -> List[Any]:
+    return list(in_dict.values())
+
+
 def env(key: str, default: Any = _DEFAULT_MARKER_) -> Optional[str]:
     """
     :param key: Environment variable key

omegaconf/omegaconf.py

@@ -93,11 +93,14 @@ def SI(interpolation: str) -> Any:
 
 
 def register_default_resolvers() -> None:
-    from .built_in_resolvers import decode, env, legacy_env
+    from .built_in_resolvers import decode, dict_keys, dict_values, env, legacy_env
+
+    OmegaConf.register_new_resolver("oc.decode", decode)
+    OmegaConf.register_new_resolver("oc.dict.keys", dict_keys)
+    OmegaConf.register_new_resolver("oc.dict.values", dict_values)
+    OmegaConf.register_new_resolver("oc.env", env)
 
     OmegaConf.legacy_register_resolver("env", legacy_env)
-    OmegaConf.register_new_resolver("oc.env", env, use_cache=False)
-    OmegaConf.register_new_resolver("oc.decode", decode, use_cache=False)
 
 
 class OmegaConf:

tests/interpolation/built_in_resolvers/test_dict.py

@@ -0,0 +1,87 @@
+from typing import Any
+
+from pytest import mark, param
+
+from omegaconf import OmegaConf
+
+
+@mark.parametrize(
+    ("cfg", "key", "expected"),
+    [
+        param(
+            {"foo": "${oc.dict.keys:{a: 0, b: 1}}"},
+            "foo",
+            OmegaConf.create(["a", "b"]),
+            id="dict",
+        ),
+        param(
+            {"foo": "${oc.dict.keys:${bar}}", "bar": {"a": 0, "b": 1}},
+            "foo",
+            OmegaConf.create(["a", "b"]),
+            id="dictconfig",
+        ),
+        param(
+            {"foo": "${sum:${oc.dict.keys:{1: one, 2: two}}}"},
+            "foo",
+            3,
+            id="nested",
+        ),
+    ],
+)
+def test_dict_keys(restore_resolvers: Any, cfg: Any, key: Any, expected: Any) -> None:
+    OmegaConf.register_new_resolver("sum", lambda x: sum(x))
+
+    cfg = OmegaConf.create(cfg)
+    val = cfg[key]
+    assert val == expected
+    assert type(val) is type(expected)
+
+
+@mark.parametrize(
+    ("cfg", "key", "expected"),
+    [
+        param(
+            {"foo": "${oc.dict.values:{a: 0, b: 1}}"},
+            "foo",
+            OmegaConf.create([0, 1]),
+            id="dict",
+        ),
+        param(
+            {"foo": "${oc.dict.values:${bar}}", "bar": {"a": 0, "b": 1}},
+            "foo",
+            OmegaConf.create([0, 1]),
+            id="dictconfig",
+        ),
+        param(
+            {"foo": "${sum:${oc.dict.values:{one: 1, two: 2}}}"},
+            "foo",
+            3,
+            id="nested",
+        ),
+        param(
+            {
+                "foo": "${oc.dict.values:${bar}}",
+                "bar": {"x": {"x0": 0, "x1": 1}, "y": {"y0": 0}},
+            },
+            "foo",
+            OmegaConf.create([{"x0": 0, "x1": 1}, {"y0": 0}]),
+            id="convert_node_to_list",
+        ),
+        param(
+            {
+                "foo": "${oc.dict.values:{key: ${val_ref}}}",
+                "val_ref": "value",
+            },
+            "foo",
+            OmegaConf.create(["value"]),
+            id="dict_with_interpolated_value",
+        ),
+    ],
+)
+def test_dict_values(restore_resolvers: Any, cfg: Any, key: Any, expected: Any) -> None:
+    OmegaConf.register_new_resolver("sum", lambda x: sum(x))
+
+    cfg = OmegaConf.create(cfg)
+    val = cfg[key]
+    assert val == expected
+    assert type(val) is type(expected)