"" (i.e. present but empty, particularly for env vars)
This allows falsy values¹ like the number 0 and boolean false to be
configurable values², as expected to be for OIDC_IAT_BACKDATED_BY and
REDIS_REQUIRED.
For example, setting REDIS_REQUIRED=false is now functional as intended
by "Allow and document how to run safely in production mode without
Redis" (64f7d92b). And setting OIDC_IAT_BACKDATED_BY=0 in the
environment now overrides any value from the config file instead of
being ignored.
² Other falsy values like NaN and 0n are also now considered
non-missing, but there's no way to express those in our current config
sources, which permit only strings or JSON values. We may find
ourselves wanting to treat NaN as missing too if config sources
change.
…instead of considering them missing.
The values considered missing are now more clear:
This allows falsy values¹ like the number 0 and boolean false to be configurable values², as expected to be for OIDC_IAT_BACKDATED_BY and REDIS_REQUIRED.
For example, setting REDIS_REQUIRED=false is now functional as intended by "Allow and document how to run safely in production mode without Redis" (64f7d92b). And setting OIDC_IAT_BACKDATED_BY=0 in the environment now overrides any value from the config file instead of being ignored.
Related-to: https://github.com/nextstrain/nextstrain.org/pull/739
¹ https://developer.mozilla.org/en-US/docs/Glossary/Falsy
² Other falsy values like NaN and 0n are also now considered non-missing, but there's no way to express those in our current config sources, which permit only strings or JSON values. We may find ourselves wanting to treat NaN as missing too if config sources change.
Checklist