starknet_api: add and use StateRoots::EMPTY

[dorimedini-starkware]

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[reviewable-StarkWare]

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PR Summary

Medium Risk
This is a small but public API change: StateRoots no longer derives Default, so any downstream code relying on StateRoots::default() will break until migrated. Runtime behavior is effectively unchanged, but the empty-root check in global_root() is now centralized via StateRoots::EMPTY.

Overview
Introduces StateRoots::EMPTY in starknet_api and removes the Default derive from StateRoots, making the empty-root representation explicit.

Updates committer tests, snap-sync CLI/tests, and the central systest blob regression helper to use StateRoots::EMPTY (including in global_root()’s empty-state branch) instead of StateRoots::default()/unwrap_or_default().

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[dorimedini-starkware]

• central_systest_blobs: add proof tx to test privacy feature #14006
• starknet_api: add and use StateRoots::EMPTY #13980 👈 (View in Graphite)
• central_systest_blobs: add some invokes #13978
• central_systest_blobs: support reverting invokes #13977
• central_systest_blobs: implement invoke from deploy function for code sharing #13976
• central_systest_blobs: deploy test contract(s) #13975
• central_systest_blobs: declare the test contract #13974
• central_systest_blobs: expect operator and fee token addresses #13973
• central_systest_blobs: deploy token contract #13972
• central_systest_blobs: sort state diff in preconfirmed block #13971
• central_systest_blobs: deploy operator account #13970
• central_systest_blobs: initial block production #13969
• central_systest_blobs: sort hashsets when dumping #13968
• central_systest_blobs: implement blob creation from blocks #13967
• central_systest_blobs: implement block production, given txs #13966
• blockifier: implement conversion from commitment state diff to state maps #13965
• central_systest_blobs: implement preconfirmed block creation #13964
• central_systest_blobs: first two bootstrap declares #13963
• central_systest_blobs: refactor skeleton into structured factory #13962
• central_systest_blobs: move blobs.json storage out of git, into GCS #13946
• apollo_consensus_orchestrator: add Deserialize for testing #13945
• main

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[dorimedini-starkware]

@dorimedini-starkware made 1 comment.
Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on nimrod-starkware and yoavGrs).

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crates/starknet_api/src/hash.rs line 104 at r2 (raw file):

Previously, nimrod-starkware wrote…

I'm not sure it makes sense to have a default value for this...
I guess there are few places where StateRoots::default() was used to indicate an empty state, IMO it's better to be explicit there and change it to StateRoots::EMPTY

I agree, removed the impl

[nimrod-starkware]

@nimrod-starkware reviewed 5 files and all commit messages, made 1 comment, and resolved 1 discussion.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on yoavGrs).

[dorimedini-starkware]

@dorimedini-starkware reviewed 2 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on yoavGrs).

[dorimedini-starkware]

@dorimedini-starkware reviewed 1 file and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on yoavGrs).