chore: compressed repr. should store disc as part of data

[SwenSchaeferjohann]

• indexer has to store the Account data as it is on-chain in the Account field of AccountInterface. this includes the discriminator
• indexer cannot stitch it together if it doesn't know the length of the discriminator
• we should support var length discriminators for eg pinocchio programs

Summary by CodeRabbit

• Bug Fixes
  • Improved consistency in account data serialization and hashing across the SDK to ensure proper alignment with on-chain protocol standards.

[coderabbitai]

📝 Walkthrough

Walkthrough

The pull request modifies discriminator handling across account interface and compressed/decompressed account data processing. Changes shift from rebuilding account data with explicit discriminator prefixes to incorporating 8-byte discriminators as direct prefixes in hashing and data construction operations.

Changes

Cohort / File(s)	Summary
Account Data Construction sdk-libs/client/src/interface/account_interface.rs	Modified hot-to-cold transition to directly clone existing on-chain data bytes instead of rebuilding with discriminator prefix. Updated doc comment clarifies that data.data contains full on-chain account bytes as-is.
Compressed Account Hashing sdk-libs/sdk-types/src/interface/program/compression/pda.rs, sdk-libs/sdk-types/src/interface/program/decompression/pda.rs	Both files now prepend 8-byte discriminator as a prefix to Borsh-serialized account data before hashing, changing hash input from Borsh(data) to DISCRIMINATOR || Borsh(data). Maintains protocol convention by zeroing first hash byte. Adds Vec allocation support for buffer construction.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• refactor: expose DECOMPRESSED_DISCRIMINATOR and pubkey in decompressed accounts #2208 — Modifies how the 8-byte PDA discriminator is handled in compressed/decompressed account data operations, including discriminator-as-prefix logic.
• refactor: AccountInterface: use photon v2 types and simplify ColdContext #2274 — Updates AccountInterface cold construction and compressed-account handling in the same affected files.

Suggested labels

ai-review

Suggested reviewers

• sergeytimoshin
• ananas-block

Poem

🔷 Eight bytes now lead the way,
Discriminators prefix play,
Hashes mirror what's on-chain,
Data flows without refrain! 🎯

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Merge Conflict Detection	⚠️ Warning	⚠️ Unable to check for merge conflicts: Failed to fetch base branch: From https://github.com/Lightprotocol/light-protocol ! [rejected] main -> main (non-fast-forward) + 2cde4dd...c7866ee main -> origin/main (forced update)

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly addresses the core change: storing the discriminator as part of the account data, which aligns with the PR objectives and all three modified files.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 70.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch swen/fix-disc-for-accountinterface

⚔️ Resolve merge conflicts (beta)

• Auto-commit resolved conflicts to branch swen/fix-disc-for-accountinterface
• Create stacked PR with resolved conflicts
• Post resolved changes as copyable diffs in a comment

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[coderabbitai]

Caution

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

⚠️ Outside diff range comments (1)

sdk-libs/sdk-types/src/interface/program/compression/pda.rs (1)

142-148: ⚠️ Potential issue | 🔴 Critical

Inconsistency in OutAccountInfo.data format between pda.rs and account.rs paths.

The data field format is inconsistent across code paths. In pda.rs (decompression), OutAccountInfo.data includes the 8-byte discriminator prefix (disc + borsh), with data_hash calculated over both. However, in account.rs (modification via to_account_info()), OutAccountInfo.data contains only the borsh serialization without the discriminator prefix, and data_hash is calculated on the account object directly.

Both paths populate the same OutAccountInfo structure, so this format mismatch will break downstream consumers. Additionally, the data_hash calculations differ between paths (pda.rs hashes disc+borsh, account.rs hashes account), which could cause validation failures. Update account.rs to mirror the pda.rs layout: include the discriminator prefix in the data field and recalculate data_hash consistently.