fixes https://github.com/spesmilo/electrum/issues/8837
Alternatively we could do a config upgrade (convert_version_*) to fix that specific issue,
but they are not safe against downgrade-upgrade-again, so probably not the best choice for
crash-inducing values.
And this kind of converter is a generic solution that can be useful for other configvars later
(though for most usages I expect we will also need a converter for the setter).
Besides a literal value, the default can now also be a callable,
which gets called with the config and evaluated as needed, lazily.
This potentially allows e.g. the default value of one configvar to
depend on the current value of another configvar.
A new config API is introduced, and ~all of the codebase is adapted to it.
The old API is kept but mainly only for dynamic usage where its extra flexibility is needed.
Using examples, the old config API looked this:
```
>>> config.get("request_expiry", 86400)
604800
>>> config.set_key("request_expiry", 86400)
>>>
```
The new config API instead:
```
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS
604800
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS = 86400
>>>
```
The old API operated on arbitrary string keys, the new one uses
a static ~enum-like list of variables.
With the new API:
- there is a single centralised list of config variables, as opposed to
these being scattered all over
- no more duplication of default values (in the getters)
- there is now some (minimal for now) type-validation/conversion for
the config values
closes https://github.com/spesmilo/electrum/pull/5640
closes https://github.com/spesmilo/electrum/pull/5649
Note: there is yet a third API added here, for certain niche/abstract use-cases,
where we need a reference to the config variable itself.
It should only be used when needed:
```
>>> var = config.cv.WALLET_PAYREQ_EXPIRY_SECONDS
>>> var
<ConfigVarWithConfig key='request_expiry'>
>>> var.get()
604800
>>> var.set(3600)
>>> var.get_default_value()
86400
>>> var.is_set()
True
>>> var.is_modifiable()
True
```
config.mempool_fees is now [] if server claims mempool is ~empty,
and None if no valid histogram has been received from server.
(previously it used to be [] in both cases)
The few other cases that used SimpleConfig.get_instance() now
either get passed a config instance, or they try to get a reference
to something else that has a reference to a config.
(see lnsweep, qt/qrcodewidget, qt/qrtextedit)
SimpleConfig claims to handle configuration options in priority
command line, user config, system config, which makes sense.
In fact it appears it used priority command line, system config,
user config.
Also, from the priority ordering, it would seem correct that a
value should be unmodifiable if and only if it's set on the command
line. Previously anything in the system config would be unmodifiable.
This patch fixes these and cleans the code up a bit. I noticed this
whilst attempting to unify the 'auto_cycle' setting.
Fixup tests accordingly.
SomberNight
Sander van Grieken
Dzhelil Rufat
Janus
Justin Turner Arthur
ThomasV
Dmitry Sorokin
Thomas König
Neil Booth
Chris Glass