Implement support for flag dependencies

Flags now support filter conditions that depend on how other flags were evaluated. This brings that support to local evaluation in posthog-python.

This commit includes unit and integration tests

Author: haacked

bin/run_integration_tests

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+#/ Usage: bin/run_integration_tests [--debug]
+#/ Description: Runs integration tests for PostHog Python SDK
+#/ Options:
+#/   --debug    Enable debug mode for verbose output
+source bin/helpers/_utils.sh
+set_source_and_root_dir
+
+ensure_virtual_env
+
+# Parse arguments
+DEBUG_MODE=false
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        --debug)
+            DEBUG_MODE=true
+            shift
+            ;;
+        --help|-h)
+            grep '^#/' "$0" | cut -c4-
+            exit 0
+            ;;
+        *)
+            error "Unknown option: $1"
+            echo "Use --help for usage information"
+            exit 1
+            ;;
+    esac
+done
+
+echo "🚀 PostHog Python SDK Integration Tests"
+echo "=" | head -c 40 | tr '\n' '='
+echo
+
+# Check if the integration test file exists
+INTEGRATION_TEST_FILE="posthog/test/integrations/test_flag_dependencies.py"
+if [ ! -f "$INTEGRATION_TEST_FILE" ]; then
+    fatal "❌ Integration test file not found: $INTEGRATION_TEST_FILE"
+fi
+
+echo "📋 Running flag dependencies integration test..."
+if [ "$DEBUG_MODE" = true ]; then
+    echo "🔍 Debug mode enabled"
+    export POSTHOG_DEBUG=true
+fi
+echo
+
+# Run the integration test
+if python "$INTEGRATION_TEST_FILE"; then
+    echo
+    echo "🎉 All integration tests passed!"
+    exit 0
+else
+    echo
+    error "💥 Integration tests failed!"
+    exit 1
+fi

posthog/client.py

@@ -20,7 +20,7 @@
     exception_is_already_captured,
     mark_exception_as_captured,
 )
-from posthog.feature_flags import InconclusiveMatchError, match_feature_flag_properties
+from posthog.feature_flags import InconclusiveMatchError, match_feature_flag_properties, build_dependency_graph, evaluate_flags_with_dependencies
 from posthog.poller import Poller
 from posthog.request import (
     DEFAULT_HOST,
@@ -179,6 +179,8 @@ def __init__(
         self.timeout = timeout
         self._feature_flags = None  # private variable to store flags
         self.feature_flags_by_key = None
+        self.dependency_graph = None  # for flag dependencies
+        self.id_to_key_mapping = None  # maps flag ID to flag key
         self.group_type_mapping = None
         self.cohorts = None
         self.poll_interval = poll_interval
@@ -303,6 +305,16 @@ def feature_flags(self, flags):
         assert self.feature_flags_by_key is not None, (
             "feature_flags_by_key should be initialized when feature_flags is set"
         )
+        
+        # Build dependency graph for flag dependencies
+        try:
+            self.dependency_graph, self.id_to_key_mapping = build_dependency_graph(self._feature_flags)
+            self.log.debug(f"Built dependency graph with {len(self.dependency_graph.flags)} flags")
+            self.log.debug(f"ID to key mapping: {self.id_to_key_mapping}")
+        except Exception as e:
+            self.log.warning(f"Failed to build dependency graph: {e}")
+            self.dependency_graph = None
+            self.id_to_key_mapping = None
 
     def get_feature_variants(
         self,
@@ -970,13 +982,14 @@ def join(self):
             posthog.join()
             ```
         """
-        for consumer in self.consumers:
-            consumer.pause()
-            try:
-                consumer.join()
-            except RuntimeError:
-                # consumer thread has not started
-                pass
+        if self.consumers:
+            for consumer in self.consumers:
+                consumer.pause()
+                try:
+                    consumer.join()
+                except RuntimeError:
+                    # consumer thread has not started
+                    pass
 
         if self.poller:
             self.poller.stop()
@@ -1135,11 +1148,13 @@ def _compute_flag_locally(
 
             focused_group_properties = group_properties[group_name]
             return match_feature_flag_properties(
-                feature_flag, groups[group_name], focused_group_properties
+                feature_flag, groups[group_name], focused_group_properties, self.cohorts,
+                self.dependency_graph, self.id_to_key_mapping
             )
         else:
             return match_feature_flag_properties(
-                feature_flag, distinct_id, person_properties, self.cohorts
+                feature_flag, distinct_id, person_properties, self.cohorts,
+                self.dependency_graph, self.id_to_key_mapping
             )
 
     def feature_enabled(
@@ -1408,8 +1423,56 @@ def _locally_evaluate_flag(
             assert self.feature_flags_by_key is not None, (
                 "feature_flags_by_key should be initialized when feature_flags is set"
             )
-            # Local evaluation
+            
+            # Check if the requested flag has experience continuity enabled
             flag = self.feature_flags_by_key.get(key)
+            if flag and flag.get("ensure_experience_continuity", False):
+                # For experience continuity flags, we must use individual evaluation
+                # which will properly raise InconclusiveMatchError and fall back to /decide
+                try:
+                    response = self._compute_flag_locally(
+                        flag,
+                        distinct_id,
+                        groups=groups,
+                        person_properties=person_properties,
+                        group_properties=group_properties,
+                    )
+                    self.log.debug(
+                        f"Successfully computed flag locally: {key} -> {response}"
+                    )
+                    return response
+                except InconclusiveMatchError as e:
+                    self.log.debug(f"Failed to compute flag {key} locally: {e}")
+                    return None
+                except Exception as e:
+                    self.log.exception(
+                        f"[FEATURE FLAGS] Error while computing variant locally: {e}"
+                    )
+                    return None
+            
+            # Check if any flags have dependencies
+            if self.dependency_graph and len(self.dependency_graph.flags) > 0:
+                # If we have dependencies, use the dependency-aware evaluation
+                try:
+                    # Evaluate all flags with dependencies to ensure dependencies are available
+                    all_results = evaluate_flags_with_dependencies(
+                        self.feature_flags,
+                        distinct_id,
+                        person_properties,
+                        self.cohorts,
+                        requested_flag_keys={key}  # Only evaluate the requested flag and its dependencies
+                    )
+                    response = all_results.get(key)
+                    if response is not None:
+                        self.log.debug(
+                            f"Successfully computed flag with dependencies: {key} -> {response}"
+                        )
+                        return response
+                except Exception as e:
+                    self.log.warning(f"Failed to evaluate flag with dependencies: {e}")
+                    # Fall back to individual evaluation
+                    
+            # Fall back to individual flag evaluation
             if flag:
                 try:
                     response = self._compute_flag_locally(