Unexpected "Results not yet available" when "Feature Flag Response" event property is a boolean

[danielbachhuber]

Bug Description

If the first feature flag you use is a boolean, then the "Feature Flag Response" event property can be set to a boolean.

Then, when you try to run an experiment later on, the query can fail with:

DB::Exception: Cannot parse boolean value here: 'control', should be 'true' or 'false' controlled by setting bool_true_representation and bool_false_representation or one of True/False/T/F/Y/N/Yes/No/On/Off/Enable/Disable/Enabled/Disabled/1/0: while converting 'control' to Bool: while executing 'FUNCTION equals(toBool(transform(toString(nullIf(nullIf(mat_$feature_flag_response, ''), 'null')), ['true', 'false'], [1, 0], NULL)) : 72, 'control' : 30) -> equals(toBool(transform(toString(nullIf(nullIf(mat_$feature_flag_response, ''), 'null')), ['true', 'false'], [1, 0], NULL)), 'control') Nullable(UInt8) : 73'. Stack trace:

The easy fix is to change "Feature Flag Response" to a string. We should probably help customers avoid this scenario, though.

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables or https://eu.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]