Remove ERC20 approval tracking

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Unreleased
  * `Governor`: fix bug caused by duplicate write of immutable entity `ProposalSupport` ([#47](https://github.com/OpenZeppelin/openzeppelin-subgraphs/pull/47))
+ * `ERC20`: remove approval tracking as it cannot be consistently tracked during `transferFrom` calls.
 
 ### 0.1.8-5 (2022-07-29)
  * `AccessControl`: fix bug caused by duplicate write of immutable entity `AccessControl` ([#38](https://github.com/OpenZeppelin/openzeppelin-subgraphs/pull/38))

src/datasources/erc20.ts

@@ -8,7 +8,6 @@ import {
 
 import {
 	Transfer as TransferEvent,
-	Approval as ApprovalEvent,
 } from '../../generated/erc20/IERC20'
 
 import {
@@ -24,7 +23,6 @@ import {
 import {
 	fetchERC20,
 	fetchERC20Balance,
-	fetchERC20Approval,
 } from '../fetch/erc20'
 
 export function handleTransfer(event: TransferEvent): void {
@@ -70,25 +68,3 @@ export function handleTransfer(event: TransferEvent): void {
 	}
 	ev.save()
 }
-
-export function handleApproval(event: ApprovalEvent): void {
-	let contract = fetchERC20(event.address)
-
-	let owner           = fetchAccount(event.params.owner)
-	let spender         = fetchAccount(event.params.spender)
-	let approval        = fetchERC20Approval(contract, owner, spender)
-	approval.valueExact = event.params.value
-	approval.value      = decimals.toDecimals(event.params.value, contract.decimals)
-	approval.save()
-
-	// let ev         = new ERC20ApprovalEvent(events.id(event))
-	// ev.emitter     = contract.id
-	// ev.transaction = transactions.log(event).id
-	// ev.timestamp   = event.block.timestamp
-	// ev.token       = token.id
-	// ev.owner       = owner.id
-	// ev.spender     = spender.id
-	// ev.approval    = approval.id
-	// ev.value       = value.value
-	// ev.save()
-}

src/fetch/erc20.ts

@@ -6,7 +6,6 @@ import {
 	Account,
 	ERC20Contract,
 	ERC20Balance,
-	ERC20Approval,
 } from '../../generated/schema'
 
 import {
@@ -62,19 +61,3 @@ export function fetchERC20Balance(contract: ERC20Contract, account: Account | nu
 
 	return balance as ERC20Balance
 }
-
-export function fetchERC20Approval(contract: ERC20Contract, owner: Account, spender: Account): ERC20Approval {
-	let id       = contract.id.toHex().concat('/').concat(owner.id.toHex()).concat('/').concat(spender.id.toHex())
-	let approval = ERC20Approval.load(id)
-
-	if (approval == null) {
-		approval                = new ERC20Approval(id)
-		approval.contract       = contract.id
-		approval.owner          = owner.id
-		approval.spender        = spender.id
-		approval.value          = constants.BIGDECIMAL_ZERO
-		approval.valueExact     = constants.BIGINT_ZERO
-	}
-
-	return approval as ERC20Approval
-}