Hide build_proof and get_backing from spec

setup.py

@@ -475,7 +475,12 @@ def get_generalized_index(ssz_class: Any, *path: Sequence[PyUnion[int, SSZVariab
     ssz_path = Path(ssz_class)
     for item in path:
         ssz_path = ssz_path / item
-    return GeneralizedIndex(ssz_path.gindex())'''
+    return GeneralizedIndex(ssz_path.gindex())
+
+
+def compute_merkle_proof_for_state(state: BeaconState,
+                                   index: GeneralizedIndex) -> Sequence[Bytes32]:
+    return build_proof(state.get_backing(), index)'''
 
 
     @classmethod
@@ -613,7 +618,11 @@ def objects_to_spec(preset_name: str,
 
     protocols_spec = '\n\n\n'.join(format_protocol(k, v) for k, v in spec_object.protocols.items())
     for k in list(spec_object.functions):
-        if "ceillog2" in k or "floorlog2" in k:
+        if k in [
+            "ceillog2",
+            "floorlog2",
+            "compute_merkle_proof_for_state",
+        ]:
             del spec_object.functions[k]
     functions = builder.implement_optimizations(spec_object.functions)
     functions_spec = '\n\n\n'.join(functions.values())

specs/altair/sync-protocol.md

@@ -22,8 +22,9 @@
   - [`is_better_update`](#is_better_update)
   - [`is_next_sync_committee_known`](#is_next_sync_committee_known)
   - [`get_safety_threshold`](#get_safety_threshold)
-  - [`get_subtree_index`](#get_subtree_index)
   - [`compute_sync_committee_period_at_slot`](#compute_sync_committee_period_at_slot)
+  - [`get_subtree_index`](#get_subtree_index)
+  - [`compute_merkle_proof_for_state`](#compute_merkle_proof_for_state)
 - [Light client initialization](#light-client-initialization)
   - [`initialize_light_client_store`](#initialize_light_client_store)
 - [Light client state updates](#light-client-state-updates)
@@ -204,6 +205,13 @@ def get_safety_threshold(store: LightClientStore) -> uint64:
     ) // 2
 ```
 
+### `compute_sync_committee_period_at_slot`
+
+```python
+def compute_sync_committee_period_at_slot(slot: Slot) -> uint64:
+    return compute_sync_committee_period(compute_epoch_at_slot(slot))
+```
+
 ### `get_subtree_index`
 
 ```python
@@ -211,11 +219,12 @@ def get_subtree_index(generalized_index: GeneralizedIndex) -> uint64:
     return uint64(generalized_index % 2**(floorlog2(generalized_index)))
 ```
 
-### `compute_sync_committee_period_at_slot`
+### `compute_merkle_proof_for_state`
 
 ```python
-def compute_sync_committee_period_at_slot(slot: Slot) -> uint64:
-    return compute_sync_committee_period(compute_epoch_at_slot(slot))
+def compute_merkle_proof_for_state(state: BeaconState,
+                                   index: GeneralizedIndex) -> Sequence[Bytes32]:
+    ...
 ```
 
 ## Light client initialization
@@ -441,7 +450,7 @@ def create_light_client_bootstrap(state: BeaconState) -> LightClientBootstrap:
             body_root=state.latest_block_header.body_root,
         ),
         current_sync_committee=state.current_sync_committee,
-        current_sync_committee_branch=build_proof(state.get_backing(), CURRENT_SYNC_COMMITTEE_INDEX)
+        current_sync_committee_branch=compute_merkle_proof_for_state(state, CURRENT_SYNC_COMMITTEE_INDEX)
     )
 ```
 
@@ -482,7 +491,7 @@ def create_light_client_update(state: BeaconState,
     # `next_sync_committee` is only useful if the message is signed by the current sync committee
     if update_attested_period == update_signature_period:
         next_sync_committee = attested_state.next_sync_committee
-        next_sync_committee_branch = build_proof(attested_state.get_backing(), NEXT_SYNC_COMMITTEE_INDEX)
+        next_sync_committee_branch = compute_merkle_proof_for_state(attested_state, NEXT_SYNC_COMMITTEE_INDEX)
     else:
         next_sync_committee = SyncCommittee()
         next_sync_committee_branch = [Bytes32() for _ in range(floorlog2(NEXT_SYNC_COMMITTEE_INDEX))]
@@ -501,7 +510,7 @@ def create_light_client_update(state: BeaconState,
         else:
             finalized_header = BeaconBlockHeader()
             assert attested_state.finalized_checkpoint.root == Bytes32()
-        finality_branch = build_proof(attested_state.get_backing(), FINALIZED_ROOT_INDEX)
+        finality_branch = compute_merkle_proof_for_state(attested_state, FINALIZED_ROOT_INDEX)
     else:
         finalized_header = BeaconBlockHeader()
         finality_branch = [Bytes32() for _ in range(floorlog2(FINALIZED_ROOT_INDEX))]

tests/core/pyspec/eth2spec/test/altair/merkle/test_single_proof.py

@@ -2,14 +2,13 @@ from eth2spec.test.context import (
     spec_state_test,
     with_altair_and_later,
 )
-from eth2spec.test.helpers.merkle import build_proof
 
 
 @with_altair_and_later
 @spec_state_test
 def test_current_sync_committee_merkle_proof(spec, state):
     yield "state", state
-    current_sync_committee_branch = build_proof(state.get_backing(), spec.CURRENT_SYNC_COMMITTEE_INDEX)
+    current_sync_committee_branch = spec.compute_merkle_proof_for_state(state, spec.CURRENT_SYNC_COMMITTEE_INDEX)
     yield "proof", {
         "leaf": "0x" + state.current_sync_committee.hash_tree_root().hex(),
         "leaf_index": spec.CURRENT_SYNC_COMMITTEE_INDEX,
@@ -28,7 +27,7 @@ def test_current_sync_committee_merkle_proof(spec, state):
 @spec_state_test
 def test_next_sync_committee_merkle_proof(spec, state):
     yield "state", state
-    next_sync_committee_branch = build_proof(state.get_backing(), spec.NEXT_SYNC_COMMITTEE_INDEX)
+    next_sync_committee_branch = spec.compute_merkle_proof_for_state(state, spec.NEXT_SYNC_COMMITTEE_INDEX)
     yield "proof", {
         "leaf": "0x" + state.next_sync_committee.hash_tree_root().hex(),
         "leaf_index": spec.NEXT_SYNC_COMMITTEE_INDEX,
@@ -47,7 +46,7 @@ def test_next_sync_committee_merkle_proof(spec, state):
 @spec_state_test
 def test_finality_root_merkle_proof(spec, state):
     yield "state", state
-    finality_branch = build_proof(state.get_backing(), spec.FINALIZED_ROOT_INDEX)
+    finality_branch = spec.compute_merkle_proof_for_state(state, spec.FINALIZED_ROOT_INDEX)
     yield "proof", {
         "leaf": "0x" + state.finalized_checkpoint.root.hex(),
         "leaf_index": spec.FINALIZED_ROOT_INDEX,

tests/core/pyspec/eth2spec/test/altair/sync_protocol/test_update_ranking.py

@@ -15,7 +15,6 @@ from eth2spec.test.helpers.light_client import (
 from eth2spec.test.helpers.state import (
     next_slots,
 )
-from eth2spec.test.helpers.merkle import build_proof
 from math import floor
 
 
@@ -27,14 +26,14 @@ def create_update(spec, test, with_next_sync_committee, with_finality, participa
 
     if with_next_sync_committee:
         next_sync_committee = attested_state.next_sync_committee
-        next_sync_committee_branch = build_proof(attested_state.get_backing(), spec.NEXT_SYNC_COMMITTEE_INDEX)
+        next_sync_committee_branch = spec.compute_merkle_proof_for_state(attested_state, spec.NEXT_SYNC_COMMITTEE_INDEX)
     else:
         next_sync_committee = spec.SyncCommittee()
         next_sync_committee_branch = [spec.Bytes32() for _ in range(spec.floorlog2(spec.NEXT_SYNC_COMMITTEE_INDEX))]
 
     if with_finality:
         finalized_header = signed_block_to_header(spec, finalized_block)
-        finality_branch = build_proof(attested_state.get_backing(), spec.FINALIZED_ROOT_INDEX)
+        finality_branch = spec.compute_merkle_proof_for_state(attested_state, spec.FINALIZED_ROOT_INDEX)
     else:
         finalized_header = spec.BeaconBlockHeader()
         finality_branch = [spec.Bytes32() for _ in range(spec.floorlog2(spec.FINALIZED_ROOT_INDEX))]

tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py

@@ -18,7 +18,6 @@ from eth2spec.test.helpers.light_client import (
 from eth2spec.test.helpers.state import (
     next_slots,
 )
-from eth2spec.test.helpers.merkle import build_proof
 
 
 @with_altair_and_later
@@ -125,7 +124,7 @@ def test_process_light_client_update_timeout(spec, state):
 
     # Sync committee is updated
     next_sync_committee = state.next_sync_committee
-    next_sync_committee_branch = build_proof(state.get_backing(), spec.NEXT_SYNC_COMMITTEE_INDEX)
+    next_sync_committee_branch = spec.compute_merkle_proof_for_state(state, spec.NEXT_SYNC_COMMITTEE_INDEX)
     # Finality is unchanged
     finality_header = spec.BeaconBlockHeader()
     finality_branch = [spec.Bytes32() for _ in range(spec.floorlog2(spec.FINALIZED_ROOT_INDEX))]
@@ -182,7 +181,7 @@ def test_process_light_client_update_finality_updated(spec, state):
     finalized_header = signed_block_to_header(spec, finalized_block)
     assert finalized_header.slot == spec.compute_start_slot_at_epoch(state.finalized_checkpoint.epoch)
     assert finalized_header.hash_tree_root() == state.finalized_checkpoint.root
-    finality_branch = build_proof(state.get_backing(), spec.FINALIZED_ROOT_INDEX)
+    finality_branch = spec.compute_merkle_proof_for_state(state, spec.FINALIZED_ROOT_INDEX)
 
     update = spec.LightClientUpdate(
         attested_header=attested_header,