Configurable decimal proxy querying - #173
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A DataId carries the decimals in byte 7, so one feed was reachable at one scale only and a second scale meant writing the feed twice. Key feed storage by the DataId with that byte cleared, and derive any other scale from the stored answer at read time. Issuing an 8 decimal view of an 18 decimal feed becomes a docs change, not a deployment. - Add domain/data_id.rs owning the layout: CanonicalId and decimals_of - Key config, permission, state and round stores by CanonicalId - Record the canonical decimals in StoredConfig at configure time - Downscale answers in latest, get_round, round_range and find_round - Reject upscaling, an out of range decimals byte, and a downscale that would truncate a non-zero answer to zero - Drop reports addressed at a non-canonical scale, with an event
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The cache masked the decimals byte to key storage, then scaled answers itself while decimals() reported the scale the caller asked for. Reading those two together was inconsistent for anyone holding the raw cache client. The cache now serves what it stores and reports the scale it stores at; the proxy derives lower scales for the id it was given. - Move decimals_of to the cache's public interface so the proxy can read the scale an id addresses - decimals() returns the scale recorded at registration, not the request - Cache reads serve stored answers unscaled and cannot fail on scale - Proxy downscales in latest_round and get_round, and reports the scale it scaled to - Proxy rejects a scale above the stored one, a decimals byte out of range, and a downscale that would truncate a non-zero answer to zero - Re-registering a canonical id at another scale fails with DecimalsMismatch, so a feed's scale is immutable once set
A config could be removed, which left rounds and feed state behind and reopened the one hole in the immutable-scale guard: remove then re-add at another decimals byte would give a feed whose history is half at one scale and half at another. Configs are now create-or-update only. A feed is taken out of service by freezing it, and its entries expire on their own once the workflow stops writing. - Drop remove_feed_configs from the admin interface and the contract - Drop the FeedConfigRemoved event; FeedConfigSet carries the new description and permissions on both create and update - configure returns unit, since a config can no longer be absent
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Only remove_feed_configs raised it, so nothing produces it now that a config cannot be removed. Reads report an absent feed as None or an empty Vec, and a report against an unconfigured feed publishes InvalidUpdatePermission rather than failing. Wire numbering now skips 102.
record read it twice: once to check the report addresses the feed at the scale it is stored at, and again to extend the config and permission TTLs. One read serves both, so the decimals check costs nothing over the TTL extension it already needed.
It is a storage key type and storage.rs was its only real consumer, so a separate domain module bought nothing. Kept in storage rather than feed so the dependency stays one way: feed uses storage, not both ways.
decimals_of sat in the cache's interface module, which is the ABI surface, and the contract had to read the decimals byte itself before configuring a feed. The layout now lives in data-feeds-common, where both contracts can reach one definition, and deriving the scale is the feed module's job. - Add data_feeds_common::data_id with DECIMALS_BYTE and decimals_of - feed::configure derives and validates the scale, returning it for the FeedConfigSet event, so the contract never touches the byte - Drop the cache's interface::data_id module and its re-export
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- Replace the CanonicalId newtype in storage with canonical() and is_same_feed() in feed.rs; store keys stay the zeroed-decimals ID - Re-home the canonical-ID unit tests under feed::canonical and cover is_same_feed - Rebuild cache_self_upgrade.wasm from current source; the stale fixture predated StoredConfig and broke both upgrade tests - Drop the NonCanonicalDecimals guard: reports are assumed to arrive at the configured decimals - Add the data-feeds CONTEXT.md glossary
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Superseded: canonical-ID approach dropped in favor of an explicit |
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Summary
Stacks on #161.
Changes
data-feeds-common: data ID layout — byte 7 encodes requested decimals as0x20 + decimals.canonical()/is_same_feed()hidden insidefeed.rs; feed configs are permanent once created.UnsupportedDecimals, errors on truncation to zero.contracts/data-feeds/CONTEXT.mdglossary; fixture regen README (pin stellar-cli v25.x).Testing
cargo testincontracts/data-feeds— 230/230 pass (183 cache, 35 proxy, 12 common), incl. upgrade tests against a self-upgrade wasm fixture rebuilt from current source.Notes
test_fixtures/README.md.