fix: segment rule with no conditions or nested rules crashes translation

`translate_rule` asserted every rule has at least one child, so a segment
rule with no conditions and no nested rules raised AssertionError and
crashed the project's segment-count refresh task. The flag engine's
`context_matches_rule` treats such a rule as always-matching, so mirror
that: build conditions and nested rules as two independent groups AND-ed
together, each vacuously true when empty, yielding TRUE for an empty rule.

This also corrects `ANY`, which the engine evaluates as
`any(conditions) AND any(rules)` rather than a single OR over the merged
set (equivalent for ALL/NONE, divergent for ANY with both groups).

Fixes FLAGSMITH-API-5Q8

beep boop

Author: khvn26

src/flagsmith_sql_flag_engine/translator.py

@@ -517,26 +517,33 @@ def translate_condition(cond: SegmentCondition, ctx: TranslateContext) -> str |
 
 
 def translate_rule(rule: SegmentRule, ctx: TranslateContext) -> str | None:
-    children: list[str] = []
+    cond_children: list[str] = []
     for cond in rule.get("conditions") or []:
         sql = translate_condition(cond, ctx)
         if sql is None:
             return None
-        children.append(f"({sql})")
+        cond_children.append(f"({sql})")
+    rule_children: list[str] = []
     for nested in rule.get("rules") or []:
         sql = translate_rule(nested, ctx)
         if sql is None:
             return None
-        children.append(f"({sql})")
-
-    assert children, "segment rule must have at least one condition or nested rule"
-    match rule["type"]:
-        case "ALL":
-            return " AND ".join(children)
-        case "ANY":
-            return " OR ".join(children)
-        case "NONE":
-            return f"NOT ({' OR '.join(children)})"
+        rule_children.append(f"({sql})")
+
+    # Mirror the engine's `context_matches_rule`: conditions and nested rules
+    # are two independent groups AND-ed together, each vacuously true when
+    # empty.
+    op = {"ALL": " AND ", "ANY": " OR ", "NONE": " OR "}[rule["type"]]
+    groups = [
+        f"NOT ({op.join(c)})" if rule["type"] == "NONE" else op.join(c)
+        for c in (cond_children, rule_children)
+        if c
+    ]
+    if not groups:
+        return "TRUE"
+    if len(groups) == 1:
+        return groups[0]
+    return " AND ".join(f"({g})" for g in groups)
 
 
 def translate_segment(segment: SegmentContext, ctx: TranslateContext) -> str | None:

tests/test_translator_unit.py

@@ -282,6 +282,18 @@ def test_translate_segment__empty_rules__returns_false() -> None:
     assert translate_segment(seg, _ctx()) == "FALSE"
 
 
+def test_translate_segment__rule_with_no_conditions_or_nested_rules__matches_all() -> None:
+    # Given
+    seg: SegmentContext = {
+        "key": "10",
+        "name": "s",
+        "rules": [{"type": "ALL", "conditions": [], "rules": []}],
+    }
+
+    # When / Then
+    assert translate_segment(seg, _ctx()) == "(TRUE)"
+
+
 def test_translate_segment__trait_key_with_hyphens__quotes_subcolumn_path() -> None:
     # Given a trait key with a hyphen (illegal as an unquoted SQL identifier)
     seg: SegmentContext = {