feat(transaction-controller): add approval-time sponsorship/signing hooks

[pedronfigueiredo]

Related pull requests

• Extension: MetaMask/metamask-extension#46060
• Mobile: MetaMask/metamask-mobile#35754

Summary

• add isSponsored and shouldSign hooks to TransactionControllerOptions['hooks'] so clients supply approval-time sponsorship and local-vs-external signing policy at the approval boundary
• keep gas-fee-token preflight in the approval flow so the controller still refreshes token quotes and native-balance fallback before deciding whether to sign
• preserve beforeSign execution even when the approved transaction ends up on the external-sign path
• keep the Core API surface focused on controller hooks rather than a separate approval-preparation helper

Public API

hooks: {
  isSponsored?: (request: { transactionMeta: TransactionMeta }) => Promise<boolean>;
  shouldSign?: (request: {
    transactionMeta: TransactionMeta;
    isSponsored: boolean;
  }) => Promise<boolean>;
  beforePublish?: (transactionMeta: TransactionMeta) => Promise<boolean>;
  beforeSign?: BeforeSignHook;
  publish?: (transactionMeta: TransactionMeta) => Promise<{ transactionHash: string }>;
  publishBatch?: PublishBatchHook;
}

Behavior decisions

• isSponsored answers whether the transaction should be treated as sponsored at approval time.
• shouldSign answers whether the controller should reserve a nonce and sign locally.
• Sponsorship no longer implies local signing.
• beforeSign still runs before gas-fee-token publication checks, even when the final path does not locally sign.

Validation

• corepack yarn workspace @metamask/transaction-controller run jest --no-watchman --no-coverage packages/transaction-controller/src/TransactionController.test.ts
• corepack yarn build

---

Note

High Risk
Reorders the post-approval signing pipeline (nonce, sponsorship, external sign, gas-fee preflight), which affects every approved transaction and coordinated extension/mobile consumers.

Overview
Adds isSponsored and shouldSign controller hooks (exported as IsSponsoredHook / ShouldSignHook) so clients decide sponsorship and local vs external signing at approval time, with defaults tied to isGasFeeSponsored and !isExternalSign.

Approval flow is reordered: mark approved → beforeSign → gas-fee-token preflight (checkGasFeeTokenBeforePublish, moved out of #signTransaction for this path) → run hooks and set isGasFeeSponsored / isExternalSign → only reserve nonce and sign when shouldSign is true; external-sign paths skip nonce lock and clear nonce. #signTransaction gains optional skips so the approval path does not duplicate those steps.

Smaller fixes: transaction batch gas estimates update from the gas-fee poller; simulation requests initialize delegation overrides when missing; getGasFeeTokens returns empty tokens when EIP-7702 pubkey or upgrade address is missing; minor getTransactions typing and removeLeadingZeroes cleanup. Tests cover hook ordering, external-sign behavior, and transactionApproved including nonce after sign.

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