Escrow: refuse offers with zero tokens or the same token on both sides - #169
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September 29, 2026 21:11
make_offer now refuses an offer with zero tokens on either side, and an offer of a token for a different amount of itself, in all four variants: - anchor and anchor-v1: ZeroAmount is checked in the handler. A same-token offer never reaches the handler, because the maker's token-A and token-B accounts would be the same account and Anchor refuses the same mutable account twice (ConstraintDuplicateMutableAccount); a test pins that. - native and quasar: ZeroAmount and SameMint are both checked in the handler, since neither refuses the duplicate on its own (quasar's token accounts are not associated token accounts, so they need not coincide). Each variant gets a test per refusal that asserts the error code and that the maker's tokens did not move. Claude-Session: https://claude.ai/code/session_01JGEoAUjMm7Evv69k46eNcn
CI showed a same-token offer never reaches make_offer's handler: both mint slots hold the same account, and loading it twice fails with AccountBorrowFailed. Drop the SameMint check, which could never run, and have the test assert the refusal that actually happens, as the Anchor variants do. Claude-Session: https://claude.ai/code/session_01JGEoAUjMm7Evv69k46eNcn
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The book's Escrow chapter says any escrow should reject offers with zero amounts and offers where both tokens are the same, and the example did not. This adds both refusals to
make_offerin all four variants, with a test for each.What each variant does
make_offerfails withZeroAmountwhen eithertoken_a_offered_amountortoken_b_wanted_amountis zero. A same-token offer was already refused before any handler runs: the maker's token-A and token-B associated token accounts would be the same account, and Anchor refuses the same mutable account twice (ConstraintDuplicateMutableAccount, 2040, in both Anchor 1.2 and 2.0). ASameMintcheck in the handler could never run, so there isn't one. A test pins the framework refusal instead.make_offerfails withZeroAmount(a newEscrowErrorstarting at 6000, like the other finance Quasar programs). A same-token offer was already refused before the handler: both mint slots hold the same account, and loading it twice fails withAccountBorrowFailed. The first CI run showed this, and the handler'sSameMintcheck was removed as unreachable. A test pins the refusal instead.make_offerfails withZeroAmountorSameMint(newEscrowErrorvariants, appended so existing codes don't move). Nothing in the native program refuses a same-token offer on its own, so here the explicit check is what does it.Tests
Each variant gets three tests: zero offered amount, zero wanted amount, and same token. Each asserts the exact error. The Anchor and native tests also assert that the maker's token-A balance didn't change (and, for native, that no offer account was created).
Verification
The Solana toolchain can't be installed in the environment this was written in (the network policy blocks
release.anza.xyz). Every variant passescargo check --testsandcargo fmt, and the tests themselves were first run by this PR's CI.🤖 Generated with Claude Code
https://claude.ai/code/session_01JGEoAUjMm7Evv69k46eNcn