feat(flags): Add relative date operators, fix numeric ops (#105)

Author: neilkakkar

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.2.0 - 2024-01-09
+
+1. Numeric property handling for feature flags now does the expected: When passed in a number, we do a numeric comparison. When passed in a string, we do a string comparison. Previously, we always did a string comparison.
+2. Add support for relative date operators for local evaluation.
+
 ## 3.1.0 - 2023-12-04
 
 1. Increase maximum event size and batch size

posthog/feature_flags.py

@@ -2,8 +2,10 @@
 import hashlib
 import logging
 import re
+from typing import Optional
 
 from dateutil import parser
+from dateutil.relativedelta import relativedelta
 
 from posthog.utils import convert_to_datetime_aware, is_valid_regex
 
@@ -117,15 +119,17 @@ def match_property(property, property_values) -> bool:
 
     override_value = property_values[key]
 
-    if operator == "exact":
-        if isinstance(value, list):
-            return override_value in value
-        return value == override_value
+    if operator in ("exact", "is_not"):
 
-    if operator == "is_not":
-        if isinstance(value, list):
-            return override_value not in value
-        return value != override_value
+        def compute_exact_match(value, override_value):
+            if isinstance(value, list):
+                return str(override_value).lower() in [str(val).lower() for val in value]
+            return str(value).lower() == str(override_value).lower()
+
+        if operator == "exact":
+            return compute_exact_match(value, override_value)
+        else:
+            return not compute_exact_match(value, override_value)
 
     if operator == "is_set":
         return key in property_values
@@ -142,41 +146,64 @@ def match_property(property, property_values) -> bool:
     if operator == "not_regex":
         return is_valid_regex(str(value)) and re.compile(str(value)).search(str(override_value)) is None
 
-    if operator == "gt":
-        return type(override_value) is type(value) and override_value > value
-
-    if operator == "gte":
-        return type(override_value) is type(value) and override_value >= value
+    if operator in ("gt", "gte", "lt", "lte"):
+        # :TRICKY: We adjust comparison based on the override value passed in,
+        # to make sure we handle both numeric and string comparisons appropriately.
+        def compare(lhs, rhs, operator):
+            if operator == "gt":
+                return lhs > rhs
+            elif operator == "gte":
+                return lhs >= rhs
+            elif operator == "lt":
+                return lhs < rhs
+            elif operator == "lte":
+                return lhs <= rhs
+            else:
+                raise ValueError(f"Invalid operator: {operator}")
 
-    if operator == "lt":
-        return type(override_value) is type(value) and override_value < value
+        parsed_value = None
+        try:
+            parsed_value = float(value)  # type: ignore
+        except Exception:
+            pass
 
-    if operator == "lte":
-        return type(override_value) is type(value) and override_value <= value
+        if parsed_value is not None and override_value is not None:
+            if isinstance(override_value, str):
+                return compare(override_value, str(value), operator)
+            else:
+                return compare(override_value, parsed_value, operator)
+        else:
+            return compare(str(override_value), str(value), operator)
 
-    if operator in ["is_date_before", "is_date_after"]:
+    if operator in ["is_date_before", "is_date_after", "is_relative_date_before", "is_relative_date_after"]:
         try:
-            parsed_date = parser.parse(value)
-            parsed_date = convert_to_datetime_aware(parsed_date)
-        except Exception:
+            if operator in ["is_relative_date_before", "is_relative_date_after"]:
+                parsed_date = relative_date_parse_for_feature_flag_matching(str(value))
+            else:
+                parsed_date = parser.parse(str(value))
+                parsed_date = convert_to_datetime_aware(parsed_date)
+        except Exception as e:
+            raise InconclusiveMatchError("The date set on the flag is not a valid format") from e
+
+        if not parsed_date:
             raise InconclusiveMatchError("The date set on the flag is not a valid format")
 
         if isinstance(override_value, datetime.datetime):
             override_date = convert_to_datetime_aware(override_value)
-            if operator == "is_date_before":
+            if operator in ("is_date_before", "is_relative_date_before"):
                 return override_date < parsed_date
             else:
                 return override_date > parsed_date
         elif isinstance(override_value, datetime.date):
-            if operator == "is_date_before":
+            if operator in ("is_date_before", "is_relative_date_before"):
                 return override_value < parsed_date.date()
             else:
                 return override_value > parsed_date.date()
         elif isinstance(override_value, str):
             try:
                 override_date = parser.parse(override_value)
                 override_date = convert_to_datetime_aware(override_date)
-                if operator == "is_date_before":
+                if operator in ("is_date_before", "is_relative_date_before"):
                     return override_date < parsed_date
                 else:
                     return override_date > parsed_date
@@ -185,7 +212,8 @@ def match_property(property, property_values) -> bool:
         else:
             raise InconclusiveMatchError("The date provided must be a string or date object")
 
-    return False
+    # if we get here, we don't know how to handle the operator
+    raise InconclusiveMatchError(f"Unknown operator {operator}")
 
 
 def match_cohort(property, property_values, cohort_properties) -> bool:
@@ -271,3 +299,33 @@ def match_property_group(property_group, property_values, cohort_properties) ->
 
         # if we get here, all matched in AND case, or none matched in OR case
         return property_group_type == "AND"
+
+
+def relative_date_parse_for_feature_flag_matching(value: str) -> Optional[datetime.datetime]:
+    regex = r"^(?P<number>[0-9]+)(?P<interval>[a-z])$"
+    match = re.search(regex, value)
+    parsed_dt = datetime.datetime.now(datetime.timezone.utc)
+    if match:
+        number = int(match.group("number"))
+
+        if number >= 10_000:
+            # Guard against overflow, disallow numbers greater than 10_000
+            return None
+
+        interval = match.group("interval")
+        if interval == "h":
+            parsed_dt = parsed_dt - relativedelta(hours=number)
+        elif interval == "d":
+            parsed_dt = parsed_dt - relativedelta(days=number)
+        elif interval == "w":
+            parsed_dt = parsed_dt - relativedelta(weeks=number)
+        elif interval == "m":
+            parsed_dt = parsed_dt - relativedelta(months=number)
+        elif interval == "y":
+            parsed_dt = parsed_dt - relativedelta(years=number)
+        else:
+            return None
+
+        return parsed_dt
+    else:
+        return None