After the upgrade to dfx v0.9.2 I noticed that the dfx build command now generates a additional file for my canisters with the extension .most
Out of curiosity, what are these .most files?
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Yeah particularly because I get errors if I redeploy after some modification.
āÆ dfx deploy --network=ic --no-wallet manager
Deploying: manager
All canisters have already been created.
Building canistersā¦
Installing canistersā¦
WARNING!
Stable interface compatibility check failed for canister āmanagerā.
Upgrade will either FAIL or LOSE some stable variable data.
ā¦/.dfx/ic/canisters/manager/manager.old.most:1.28-1.36: type error [M0029], unbound type BucketId
Do you want to proceed? yes/No
Looks like it might have to do with a new stable types upgrade compatibility feature.
My guess itās the stable type is not compatible with changes made
--stable-types: emit signature of stable types to .most file
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Note that thereās a bug in the moc version dfx 0.9.2 uses (you can ignore the warning if youāre confident youāve not made any breaking changes), see here:
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Indeed it look like I can safely ignore the warning. I actually did loose some stable variables today but itās because I am an idiot 
.
Regarding my original question, I then understand that .most files are files that contain the candid representation of stable variables / types of my canisters.
Almost, itās actually not Candid, but a Motoko type signature for the stable variables and goes beyond Candid by allowing mutable data and parameterized type definitions.
The Motoko data is itself stored in an extended Candid format, but thatās an implementation detail that is likely to change in future (without affecting external behaviour).
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What does most stand for? My guess is āmotoko stable typesā but Iām not confidentā¦
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Yep.
Are we at 20 characters yet?