Inconsistent required_approval_index when loading from disk

[abitmore]

Bug Description

The secondary index class required_approval_index has an empty overridden member function about_to_modify(obj) as well as an empty object_modified(obj) function, combined with the logic in object_inserted(obj), may lead to inconsistent chain state and memory leak when reloading data from disk.

bitshares-core/libraries/chain/include/graphene/chain/proposal_object.hpp

Lines 76 to 77 in 623aea2

	virtual void about_to_modify( const object& before ) override{};
	virtual void object_modified( const object& after ) override{};

bitshares-core/libraries/chain/proposal_object.cpp

Lines 62 to 65 in 623aea2

	for( const auto& a : p.available_active_approvals )
	_account_to_proposals[a].insert( p.id );
	for( const auto& a : p.available_owner_approvals )
	_account_to_proposals[a].insert( p.id );

The misbehavior is reported by Mobile App Dev Team (btspp / @syalon).

The misbehavior can be corrected and avoided with a replay.

Steps To Reproduce

Steps to reproduce the behavior:

1. Setup a multi-auth account Alice, with Bob and Cindy in active authorities, both have a weight below threshold
2. Create a proposal that requires Alice's approval

• Pair (Alice,proposal) will be inserted into required_approval_index

3. Approve the proposal with Bob

• required_approval_index won't be updated

4. Stop witness_node after Bob's approval is irreversible
5. Start witness_node

• Pair (Alice,proposal) and (Bob,proposal) will be inserted into required_approval_index

6. Remove Bob's approval from the proposal

• required_approval_index won't be updated

7. Let the proposal expire

• Pair (Alice,proposal) will be removed from required_approval_index, but pair (Bob,proposal) will be kept in memory

8. Query Bob's account info with get_full_accounts API, see "Unable to find object" error

Impacts
Describe which portion(s) of BitShares Core may be impacted by this bug. Please tick at least one box.

• API (the application programming interface)
• Build (the build process or something prior to compiled code)
• CLI (the command line wallet)
• Deployment (the deployment process after building such as Docker, Travis, etc.)
• DEX (the Decentralized EXchange, market engine, etc.)
• P2P (the peer-to-peer network for transaction/block propagation)
• Performance (system or user efficiency, etc.)
• Protocol (the blockchain logic, consensus, validation, etc.)
• Security (the security of system or user data, etc.)
• UX (the User Experience)
• Other (please add below)

CORE TEAM TASK LIST

• Evaluate / Prioritize Bug Report
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation

[pmconrad]

Nice find, thanks.

I wouldn't call it "inconsistent chain state" since only API queries are affected, not the consensus-related state.

[pmconrad]

Merged #1719