clan_lib select: fix maybe select storing miss as {}

pkgs/clan-cli/clan_lib/flake/flake.py

@@ -594,6 +594,10 @@ class FlakeCacheEntry:
             if not isinstance(selector.value, str):
                 msg = f"Expected str for STR selector value in select, got {type(selector.value)}"
                 raise ClanError(msg)
+            # If the entry was previously marked as non-existent by a MAYBE selector,
+            # we should raise KeyError for STR selectors
+            if selector.value in self.value and not self.value[selector.value].exists:
+                raise KeyError(selector.value)
             return self.value[selector.value].select(selectors[1:])
 
         # if we are a MAYBE selector, we check if the key exists in the dict
@@ -1130,7 +1134,15 @@ class Flake:
         else:
             log.debug(f"$ clan select {shlex.quote(selector)}")
 
-        return self._cache.select(selector)
+        try:
+            return self._cache.select(selector)
+        except KeyError as e:
+            # Convert KeyError to ClanSelectError for consistency
+            raise ClanSelectError(
+                flake_identifier=self.identifier,
+                selectors=[selector],
+                description=f"Attribute '{e.args[0]}' not found in flake",
+            ) from e
 
     def machine_selector(self, machine_name: str, selector: str) -> str:
         """Create a selector for a specific machine.

pkgs/clan-cli/clan_lib/flake/flake_cache_test.py

@@ -7,6 +7,7 @@ import pytest
 from clan_cli.tests.fixtures_flakes import ClanFlake, create_test_machine_config
 
 from clan_lib.flake.flake import (
+    ClanSelectError,
     Flake,
     FlakeCache,
     FlakeCacheEntry,
@@ -539,3 +540,15 @@ def test_reinserting_store_path_value() -> None:
     assert isinstance(cache.value, dict)
     assert "outPath" in cache.value
     assert cache.value["outPath"].value == pure_path
+
+
+@pytest.mark.with_core
+def test_get_nonexistant_after_maybe(flake: ClanFlake) -> None:
+    """Test that if a nonexistant value is cached,
+    that the cache miss is not falsely stored as the value.
+    """
+    my_flake = Flake(str(flake.path))
+
+    my_flake.select("?nonExist")
+    with pytest.raises(ClanSelectError):
+        my_flake.select("nonExist")