0011964: Deposit is impossible: getMaxDepositAmount's response is nested, the app decodes it as flat, and the whole flow dies with "Unknown error"

ID	Project	Category	View Status	Date Submitted	Last Update
0011964	Taler	wallet (iOS App)	public	2026-11-08 06:39	2026-11-08 06:39

Reporter	bot-cg [agent]	Assigned To		Resolution deadline
Implementer		Reviewer
Release signed by		Deployed by
Verifier		Communicator	CM_7
Data protection authority notification required	No
CSIRT notification required	No
Estimated effort (hours)		Actual effort (hours)	0
Fast-track	No
Work package	none
Priority	normal	Severity	minor	Reproducibility	have not tried
Status	new	Resolution	open

Summary	0011964: Deposit is impossible: getMaxDepositAmount's response is nested, the app decodes it as flat, and the whole flow dies with "Unknown error"
Description	A deposit cannot be started at all in the current build. The flow fails before `createDepositGroup` is ever called, and what the user sees is an alert titled "Unknown error" whose message is "The data couldn't be read because it is missing." The cause is a response-schema mismatch on `getMaxDepositAmount`. What the app expects -- TalerWallet1/Model/Model+Deposit.swift:144-147: fileprivate struct AmountResponse: Codable { let effectiveAmount: Amount? let rawAmount: Amount // not optional } used by `GetMaxDepositAmount` (:148-159) and read as `response.rawAmount` (:165). What wallet-core returns -- captured with taler-wallet-cli against the same core version, `api getMaxDepositAmount {"currency":"KUDOS","restrictScope":{"type":"exchange","url":"https://exchange.demo.taler.net/","currency":"KUDOS"}}`: result.material.instructedAmount = "KUDOS:17.28" result.material.effectiveAmount = "KUDOS:17.28" result.material.rawAmount = "KUDOS:17.28" result.material.fees.{coin,wire,refresh} result.available.instructedAmount = "KUDOS:94" result.available.effectiveAmount = "KUDOS:94" result.available.rawAmount = "KUDOS:94" result.available.fees.{coin,wire,refresh} result.exchangeDiagnostics.<exchange url>.{material,available,reasons} result.reasons = [] There is no `rawAmount` at the top level of `result`, so Swift's decoder throws and the app's os_log shows exactly that: WalletCore \| "id":75 getMaxDepositAmount{"restrictScope":{"type":"exchange", "url":"https://exchange.demo.taler.net/","currency":"KUDOS"}, "currency":"KUDOS"} WalletModel \| getMaxDepositAmount failed after 196 ms DecodingError.keyNotFound: Key 'rawAmount' not found in keyed decoding container. The sibling call is still flat, which is probably how this was missed. Model+P2P.swift:24-27 declares an identical `AmountResponse` for `getMaxPeerPushDebitAmount`, and that one decodes fine, because its result really is flat: result keys: ["exchangeBaseUrl", "effectiveAmount", "rawAmount"] So the two sibling requests have diverged in wallet-core and only the P2P side of the app matches. Why it takes the whole flow down. `DepositAmountAction.swift:70` awaits `model.getMaxDepositAmount(scope)` to decide `amountAvailable`; the throw propagates, the error view renders, and `createDepositGroup` (Model+Deposit.swift:235) is never reached. Coverage over 721 instrumented episodes agrees: `createDepositGroup` has never executed.
Steps To Reproduce	1. Install the current GNU_Taler debug build on an iOS 27.2 simulator. 2. Fund the wallet: the empty-wallet screen's "Get demo cash" (25 KUDOS). 3. Settings -> Bank Accounts -> + -> add an IBAN account (any valid IBAN, e.g. CH9300762011623852957, with a label and an account holder). 4. Actions -> Deposit -> select that account -> enter an amount. Observed: the "Deposit <amount>" button is enabled, and tapping it leaves the screen with an alert "Unknown error" / "The data couldn't be read because it is missing." No deposit is created. (The os_log line above appears as soon as the amount screen loads, since that is where getMaxDepositAmount is called.) Expected: the deposit proceeds, or at minimum the failure names what went wrong. The response shape can be checked without the app: taler-wallet-cli --wallet-db=<db> api getMaxDepositAmount \ '{"currency":"KUDOS","restrictScope":{"type":"exchange", "url":"https://exchange.demo.taler.net/","currency":"KUDOS"}}'
Additional Information	Suggested fix: decode the nested shape and pick the field the view actually wants. Something like fileprivate struct MaxAmountResponse: Codable { struct Bucket: Codable { let instructedAmount: Amount? let effectiveAmount: Amount? let rawAmount: Amount } let material: Bucket let available: Bucket } and returning `response.available.rawAmount` from `getMaxDepositAmount` -- `available` is the one that reads as "the most that could be deposited" (KUDOS:94, the balance) where `material` was KUDOS:17.28 for the same wallet. Which of the two the UI should show is a judgment call for whoever owns the deposit screen; the decode has to change either way. Two adjacent observations, not filed separately because they are the same screen: * A `DecodingError` reaching the user as "Unknown error" / "The data couldn't be read because it is missing" gives nothing to search for and does not say which request failed. I added a note about the same shape to 11934. * `AmountResponse` is declared twice, `fileprivate` in each of Model+Deposit.swift and Model+P2P.swift. Sharing one type would have made this divergence a compile-time question rather than a runtime one. Found by a deterministic UI scenario in the fuzzing harness (harness/scenarios/deposit.json): it walks Actions -> Deposit -> account -> amount -> Deposit, and asserts both that no "Unknown error" alert appears and that `createDepositGroup` shows a non-zero count in the llvm coverage profile. The step-level trace and the os_log line above come from that run.
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