Implement setting config variables that contain the dot in name

dask/config.py

@@ -272,7 +272,7 @@ def collect_env(env: Mapping[str, str] | None = None) -> dict:
 
     for name, value in env.items():
         if name.startswith("DASK_"):
-            varname = name[5:].lower().replace("__", ".")
+            varname = name[5:].lower().replace("__", ".").replace("--", "__")
             d[varname] = interpret_value(value)
 
     result: dict = {}
@@ -429,7 +429,11 @@ def __init__(
             if arg is not None:
                 for key, value in arg.items():
                     key = check_deprecations(key)
-                    self._assign(key.split("."), value, config)
+                    self._assign(
+                        [s.replace("__", ".") for s in key.split(".")],
+                        value,
+                        config,
+                    )
             if kwargs:
                 for key, value in kwargs.items():
                     key = key.replace("__", ".")

dask/tests/test_config.py

@@ -227,6 +227,7 @@ def test_env():
         "DASK_E__Y": "456",
         "DASK_F": '[1, 2, "3"]',
         "DASK_G": "/not/parsable/as/literal",
+        "DASK_G--A": "any",
         "FOO": "not included",
     }
 
@@ -237,6 +238,7 @@ def test_env():
         "e": {"x": 123, "y": 456},
         "f": [1, 2, "3"],
         "g": "/not/parsable/as/literal",
+        "g.a": "any",
     }
 
     res = collect_env(env)
@@ -333,8 +335,8 @@ def test_set():
         assert config["abc"] == 123
     assert "abc" not in config
 
-    with dask.config.set({"abc.x": 1, "abc.y": 2, "abc.z.a": 3}):
-        assert config["abc"] == {"x": 1, "y": 2, "z": {"a": 3}}
+    with dask.config.set({"abc.x": 1, "abc.y": 2, "abc.z.a": 3, "abc.z.a__a": 4}):
+        assert config["abc"] == {"x": 1, "y": 2, "z": {"a": 3, "a.a": 4}}
     assert "abc" not in config
 
     d = {}