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fix: Enrich captured events with locally evaluated flags #229

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fix: Enrich captured events with locally evaluated flags #229

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160f105
Enrich captured events with local evaluation
Josh-IE Apr 24, 2025
d89c5b4
Update tests
Josh-IE Apr 24, 2025
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12 changes: 5 additions & 7 deletions posthog/client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -479,17 +479,15 @@ def capture(

extra_properties: dict[str, Any] = {}
feature_variants: Optional[dict[str, Union[bool, str]]] = {}
if send_feature_flags:
try:
feature_variants = self.get_feature_variants(distinct_id, groups, disable_geoip=disable_geoip)
except Exception as e:
self.log.exception(f"[FEATURE FLAGS] Unable to get feature variants: {e}")

elif self.feature_flags and event != "$feature_flag_called":
if self.feature_flags and event != "$feature_flag_called":
# Local evaluation is enabled, flags are loaded, so try and get all flags we can without going to the server
feature_variants = self.get_all_flags(
distinct_id, groups=(groups or {}), disable_geoip=disable_geoip, only_evaluate_locally=True
)
elif send_feature_flags:
feature_variants = self.get_all_flags(
distinct_id, groups=(groups or {}), disable_geoip=disable_geoip, only_evaluate_locally=False
)

for feature, variant in (feature_variants or {}).items():
extra_properties[f"$feature/{feature}"] = variant
Expand Down
263 changes: 247 additions & 16 deletions posthog/test/test_client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -271,12 +271,56 @@ def test_capture_exception_logs_when_enabled(self):
self.assertEqual(logs.output[0], "ERROR:posthog:test exception\nNoneType: None")
self.assertEqual(getattr(logs.records[0], "path"), "one/two/three")

@mock.patch("posthog.client.get")
@mock.patch("posthog.client.flags")
def test_basic_capture_with_feature_flags(self, patch_flags):
def test_basic_capture_with_feature_flags(self, patch_flags, patch_get):
patch_flags.return_value = {"featureFlags": {"beta-feature": "random-variant"}}
patch_get.return_value = {
"flags": [
{
"id": 2,
"team_id": 1,
"name": "Beta Feature",
"key": "beta-feature",
"filters": {
"groups": [
{
"properties": [],
"rollout_percentage": None
}
],
"payloads": {},
"multivariate": {
"variants": [
{
"key": "random-variant",
"rollout_percentage": 100
},
{
"key": "test",
"rollout_percentage": 0
}
]
}
},
"deleted": False,
"active": True,
"ensure_experience_continuity": False,
"has_encrypted_payloads": False,
"version": 2
}
],
"group_type_mapping": {
"0": "account",
"1": "organization",
"2": "instance",
"3": "project"
},
"cohorts": {}
}

client = Client(FAKE_TEST_API_KEY, on_error=self.set_fail, personal_api_key=FAKE_TEST_API_KEY)
success, msg = client.capture("distinct_id", "python test event", send_feature_flags=True)
success, msg = client.capture("distinct_id", "python test event")
client.flush()
self.assertTrue(success)
self.assertFalse(self.failed)
Expand All @@ -287,14 +331,19 @@ def test_basic_capture_with_feature_flags(self, patch_flags):
self.assertEqual(msg["distinct_id"], "distinct_id")
self.assertEqual(msg["properties"]["$lib"], "posthog-python")
self.assertEqual(msg["properties"]["$lib_version"], VERSION)
self.assertEqual(msg["properties"]["$feature/beta-feature"], "random-variant")
self.assertEqual(msg["properties"]["$active_feature_flags"], ["beta-feature"])

self.assertEqual(patch_flags.call_count, 1)
# Feature flag is not sent, because client.feature_flags is unset and send_feature_flags=False
assert "$feature/beta-feature" not in msg["properties"]
assert "$active_feature_flags" not in msg["properties"]
self.assertEqual(patch_flags.call_count, 0)
self.assertEqual(patch_get.call_count, 0)

@mock.patch("posthog.client.get")
@mock.patch("posthog.client.flags")
def test_basic_capture_with_locally_evaluated_feature_flags(self, patch_flags):
def test_basic_capture_with_locally_evaluated_feature_flags(self, patch_flags, patch_get):
patch_flags.return_value = {"featureFlags": {"beta-feature": "random-variant"}}
patch_get.return_value = {"flags": []}

client = Client(FAKE_TEST_API_KEY, on_error=self.set_fail, personal_api_key=FAKE_TEST_API_KEY)

multivariate_flag = {
Expand Down Expand Up @@ -375,23 +424,205 @@ def test_basic_capture_with_locally_evaluated_feature_flags(self, patch_flags):
self.assertEqual(msg["distinct_id"], "distinct_id")
self.assertEqual(msg["properties"]["$lib"], "posthog-python")
self.assertEqual(msg["properties"]["$lib_version"], VERSION)

# Feature flag is sent despite send_feature_flags=False
# because client.feature_flags is set
self.assertEqual(msg["properties"]["$feature/beta-feature-local"], "third-variant")
self.assertEqual(msg["properties"]["$feature/false-flag"], False)
self.assertEqual(msg["properties"]["$active_feature_flags"], ["beta-feature-local"])
assert "$feature/beta-feature" not in msg["properties"]

# There are no calls to (/flags, /decide) or /api/feature_flag/local_evaluation
self.assertEqual(patch_flags.call_count, 0)
self.assertEqual(patch_get.call_count, 0)

# test that flags are not evaluated without local evaluation
client.feature_flags = []
success, msg = client.capture("distinct_id", "python test event")
@mock.patch("posthog.client.get")
@mock.patch("posthog.client.flags")
def test_basic_capture_with_local_evaluation_and_send_feature_flags(self, patch_flags, patch_get):
patch_flags.return_value = {"featureFlags": {"beta-feature": "random-variant"}}
patch_get.return_value = {
"flags": [
{
"id": 2,
"team_id": 1,
"name": "Beta Feature",
"key": "beta-feature",
"filters": {
"groups": [
{
"properties": [],
"rollout_percentage": None
}
],
"payloads": {},
"multivariate": {
"variants": [
{
"key": "random-variant",
"rollout_percentage": 100
},
{
"key": "test",
"rollout_percentage": 0
}
]
}
},
"deleted": False,
"active": True,
"ensure_experience_continuity": False,
"has_encrypted_payloads": False,
"version": 2
}
],
"group_type_mapping": {
"0": "account",
"1": "organization",
"2": "instance",
"3": "project"
},
"cohorts": {}
}

client = Client(FAKE_TEST_API_KEY, on_error=self.set_fail, personal_api_key=FAKE_TEST_API_KEY)

multivariate_flag = {
"id": 1,
"name": "Beta Feature",
"key": "beta-feature-local",
"active": True,
"rollout_percentage": 100,
"filters": {
"groups": [
{
"properties": [
{"key": "email", "type": "person", "value": "test@posthog.com", "operator": "exact"}
],
"rollout_percentage": 100,
},
{
"rollout_percentage": 50,
},
],
"multivariate": {
"variants": [
{"key": "first-variant", "name": "First Variant", "rollout_percentage": 50},
{"key": "second-variant", "name": "Second Variant", "rollout_percentage": 25},
{"key": "third-variant", "name": "Third Variant", "rollout_percentage": 25},
]
},
"payloads": {"first-variant": "some-payload", "third-variant": {"a": "json"}},
},
}
basic_flag = {
"id": 1,
"name": "Beta Feature",
"key": "person-flag",
"active": True,
"filters": {
"groups": [
{
"properties": [
{
"key": "region",
"operator": "exact",
"value": ["USA"],
"type": "person",
}
],
"rollout_percentage": 100,
}
],
"payloads": {"true": 300},
},
}
false_flag = {
"id": 1,
"name": "Beta Feature",
"key": "false-flag",
"active": True,
"filters": {
"groups": [
{
"properties": [],
"rollout_percentage": 0,
}
],
"payloads": {"true": 300},
},
}
client.feature_flags = [multivariate_flag, basic_flag, false_flag]

# test that flags are evaluated locally without calling /flags or /decide
success, msg = client.capture("distinct_id", "python test event", send_feature_flags=True)
client.flush()
self.assertTrue(success)
self.assertFalse(self.failed)

self.assertEqual(msg["event"], "python test event")
self.assertTrue(isinstance(msg["timestamp"], str))
self.assertIsNone(msg.get("uuid"))
self.assertEqual(msg["distinct_id"], "distinct_id")
self.assertEqual(msg["properties"]["$lib"], "posthog-python")
self.assertEqual(msg["properties"]["$lib_version"], VERSION)
self.assertEqual(msg["properties"]["$feature/beta-feature-local"], "third-variant")
self.assertEqual(msg["properties"]["$feature/false-flag"], False)
self.assertEqual(msg["properties"]["$active_feature_flags"], ["beta-feature-local"])
assert "$feature/beta-feature" not in msg["properties"]
assert "$feature/beta-feature-local" not in msg["properties"]
assert "$feature/false-flag" not in msg["properties"]
assert "$active_feature_flags" not in msg["properties"]

# There are no calls to (/flags, /decide) or /api/feature_flag/local_evaluation
# because client.feature_flags is set.
self.assertEqual(patch_flags.call_count, 0)
self.assertEqual(patch_get.call_count, 0)

# Test that flags are evaluated with only call to local evaluation (/api/feature_flag/local_evaluation)
# Create a new client, so that client.feature_flags is None
client = Client(FAKE_TEST_API_KEY, on_error=self.set_fail, personal_api_key=FAKE_TEST_API_KEY)
success, msg = client.capture("distinct_id", "python test event", send_feature_flags=True)
client.flush()
self.assertTrue(success)
self.assertFalse(self.failed)
self.assertEqual(msg["properties"]["$feature/beta-feature"], "random-variant")
self.assertEqual(msg["properties"]["$active_feature_flags"], ["beta-feature"])
self.assertEqual(patch_get.call_count, 1)
self.assertEqual(patch_flags.call_count, 0)

@mock.patch("posthog.client.get")
@mock.patch("posthog.client.flags")
def test_basic_capture_with_local_evaluation_and_fallback_to_decide(self, patch_flags, patch_get):
patch_flags.return_value = {"featureFlags": {"beta-feature": "random-variant"}}
patch_get.return_value = {"flags": []}

client = Client(FAKE_TEST_API_KEY, on_error=self.set_fail, personal_api_key=FAKE_TEST_API_KEY)
success, msg = client.capture("distinct_id", "python test event", send_feature_flags=True)
client.flush()
self.assertTrue(success)
self.assertFalse(self.failed)
self.assertEqual(msg["properties"]["$feature/beta-feature"], "random-variant")
self.assertEqual(msg["properties"]["$active_feature_flags"], ["beta-feature"])

# Both (/flags, /decide) and /api/feature_flag/local_evaluation are called
self.assertEqual(patch_get.call_count, 1)
self.assertEqual(patch_flags.call_count, 1)

@mock.patch("posthog.client.get")
@mock.patch("posthog.client.flags")
def test_basic_capture_with_local_evaluation_disabled(self, patch_flags, patch_get):
patch_flags.return_value = {"featureFlags": {"beta-feature": "random-variant"}}
patch_get.return_value = {"flags": []}

# Creating client without personal_api_key disables local evaluation
client = Client(FAKE_TEST_API_KEY, on_error=self.set_fail)
success, msg = client.capture("distinct_id", "python test event", send_feature_flags=True)
client.flush()
self.assertTrue(success)
self.assertFalse(self.failed)
self.assertEqual(msg["properties"]["$feature/beta-feature"], "random-variant")
self.assertEqual(msg["properties"]["$active_feature_flags"], ["beta-feature"])

# Only (/flags, /decide) is called. /api/feature_flag/local_evaluation is not called
self.assertEqual(patch_flags.call_count, 1)
self.assertEqual(patch_get.call_count, 0)

@mock.patch("posthog.client.get")
def test_load_feature_flags_quota_limited(self, patch_get):
Expand Down Expand Up @@ -519,8 +750,8 @@ def test_basic_capture_with_feature_flags_returns_active_only(self, patch_flags)
timeout=3,
distinct_id="distinct_id",
groups={},
person_properties=None,
group_properties=None,
person_properties={"distinct_id": "distinct_id"},
group_properties={},
disable_geoip=True,
)

Expand Down Expand Up @@ -561,8 +792,8 @@ def test_basic_capture_with_feature_flags_and_disable_geoip_returns_correctly(se
timeout=12,
distinct_id="distinct_id",
groups={},
person_properties=None,
group_properties=None,
person_properties={"distinct_id": "distinct_id"},
group_properties={},
disable_geoip=False,
)

Expand Down