fix: create missing Pool on demand to avoid null-Pool abort

[rickstaa]

Problem

reward() aborts on a null Pool (the halt at block 144056642) and ticketBroker silently drops the fees when a round's Pool was never built. newRound builds Pools by walking the on-chain pool with an eth_call enumeration, which is non-deterministic and can come up short. See #248 for the root cause.

Fix

Add createOrLoadPool(round, transcoderAddress) and use it in newRound, reward, and ticketBroker, so the Pool is always built through one code path and no handler aborts on a null Pool.

• Single writer — the helper is the only place a Pool is created, setting the round snapshot (totalStake/rewardCut/feeShare) once. Handlers only add their own accumulator (reward → rewardTokens, ticketBroker → fees), never re-touching the snapshot.
• No ! — the helper returns a non-null Pool and defaults the non-nullable fields if the Transcoder is ever missing, so save() can't abort (matches The Graph's unexpected-null linter guidance).
• Unchanged on a full sync — the transcoder always exists (from Bond/register logs), so Pools get real values. The default branch is a failsafe.

Notes

• Pool fix only. Ship together with the Transaction.to nullable fix (fix: make Transaction.to nullable for contract-creation txs #245) — 144056642 comes before the to-bug block (485100965).
• Cross-indexer POI consistency of Pools needs a reliable enumeration — that is Non-deterministic eth_call reads silently corrupt indexing (POI divergence) #248.

[coderabbitai]

📝 Walkthrough

Walkthrough

This change adds a shared createOrLoadPool helper and updates round initialization, reward processing, and ticket redemption to use it for deterministic Pool creation, loading, field updates, and persistence.

Changes

Pool lifecycle centralization

Layer / File(s)	Summary
Shared pool creation and loading utils/helpers.ts	Adds createOrLoadPool, which loads an existing pool or initializes and saves one using round and transcoder data.
Round pool initialization src/mappings/roundsManager.ts	Replaces inline Pool construction in newRound with the shared helper.
Reward and ticket pool updates src/mappings/bondingManager.ts, src/mappings/ticketBroker.ts	Uses the shared helper for pool retrieval and applies reward, fee-share, reward-cut, and fee updates directly to the returned pool.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• livepeer/subgraph#246: Addresses null Pool handling by creating pools on demand when storage loading returns null.

Sequence Diagram(s)

sequenceDiagram
  participant RoundHandler
  participant RewardHandler
  participant TicketHandler
  participant createOrLoadPool
  participant PoolStore

  RoundHandler->>createOrLoadPool: Initialize pool for active transcoder
  RewardHandler->>createOrLoadPool: Retrieve pool for reward
  TicketHandler->>createOrLoadPool: Retrieve pool for ticket fees
  createOrLoadPool->>PoolStore: Load or save pool
  createOrLoadPool-->>RewardHandler: Pool entity for reward updates
  createOrLoadPool-->>TicketHandler: Pool entity for fee updates

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: creating missing Pools on demand to prevent null-Pool aborts.
Description check	✅ Passed	The description covers the problem, fix, context, and dependencies, but it omits the template checklist and an explicit Fixes # line.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/create-or-load-pool

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[github-actions]

🚀 Subgraph Studio preview deployed

Item	Details
Version label	pr-249-8d58daf-29782364581
Query endpoint	https://api.studio.thegraph.com/query/31909/livepeer-ci/pr-249-8d58daf-29782364581

curl -H 'Content-Type: application/json' \
  -d '{"query":"{ protocol(id: \"0\") { inflation } }"}' \
  https://api.studio.thegraph.com/query/31909/livepeer-ci/pr-249-8d58daf-29782364581

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/mappings/ticketBroker.ts (1)

68-71: 🎯 Functional Correctness | 🔴 Critical | ⚡ Quick win

Fix erroneous reserve deduction due to premature zeroing of deposit.

broadcaster.deposit is reassigned to ZERO_BD before it is subtracted from faceValue to calculate the difference. Consequently, the difference evaluates to the entire faceValue, leading to an over-deduction from the broadcaster's reserve. Calculate the difference before resetting the deposit.

🐛 Proposed fix

   if (faceValue.gt(broadcaster.deposit)) {
-    broadcaster.deposit = ZERO_BD;
-
-    let difference = faceValue.minus(broadcaster.deposit);
+    let difference = faceValue.minus(broadcaster.deposit);
+    broadcaster.deposit = ZERO_BD;
     if (difference.gt(broadcaster.reserve)) {

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/mappings/ticketBroker.ts` around lines 68 - 71, In the
insufficient-deposit branch, calculate difference using the original
broadcaster.deposit before assigning ZERO_BD. Update the sequence around
broadcaster.deposit and difference so the reserve deduction reflects only the
uncovered amount, then reset broadcaster.deposit to ZERO_BD.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@src/mappings/ticketBroker.ts`:
- Around line 68-71: In the insufficient-deposit branch, calculate difference
using the original broadcaster.deposit before assigning ZERO_BD. Update the
sequence around broadcaster.deposit and difference so the reserve deduction
reflects only the uncovered amount, then reset broadcaster.deposit to ZERO_BD.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 54c63cbb-bd7c-462a-8efc-e8566a4022c1

📥 Commits

Reviewing files that changed from the base of the PR and between 2eac27f and 38d1b9a.

📒 Files selected for processing (4)

• src/mappings/bondingManager.ts
• src/mappings/roundsManager.ts
• src/mappings/ticketBroker.ts
• utils/helpers.ts