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feat(drive): compute what creating a document costs for the SDKs - #5159

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Sep 28, 2026
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@QuantumExplorer QuantumExplorer commented Sep 28, 2026 •

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Basic explanation

What this does: Creating a document costs credits: mostly storage (every byte the insert writes, 27,000 credits a byte), some processing, and whatever the contract adds (an action fee, a token cost, a contest's vote fund). Until now nobody could say what a document of a given type costs without inserting one on a node. This PR adds a function that computes it from the contract alone, with Drive's own rules: document_create_cost in rs-drive, exposed to JavaScript as documentCreateCost(contract, documentTypeName, options, platformVersion) in wasm-sdk, and so in @dashevo/evo-sdk. The contract visualizer uses it to show the cost of each document type in Dash and dollars.

Value:

  • App developers and reviewers see what a document costs before shipping a contract, and what each index adds: its layers shared with other indexes (paid once) and its own.
  • The storage is exact, not a guess. A test inserts documents into 19 contracts and requires the estimate to equal the storage fee Drive charged, byte for byte.
  • Everything else a create pays is mapped out too: the processing (fixed parts exact, the rest estimated), the contract's charges, and what a delete refunds.

Risks: Low, and no consensus change.

  • New code only computes; it writes nothing and runs in no block.
  • Helpers the estimate shares with the insert path moved so the verify build (the one wasm-sdk uses) can call them, unchanged: the document reference builders, the indexOnly member key, the preallocation width check, and the tier lookup of document_ttl_pricing. The full rs-drive library suite passes.
  • wasm-sdk now builds rs-drive with fee-distribution (for the refund), which adds rust_decimal: with the estimate, the compressed SDK is about 40 KB larger than the layout PR's build (12.80 MB to 12.84 MB).

Issue being fixed or feature implemented

The contract visualizer needs to show what a document of each type costs, per index, in Dash and dollars, and let a reader refine it by the fields that matter. Drive's own fee estimation (add_document_for_contract with apply = false) needs GroveDB's RocksDB storage, so it cannot run in a browser.

What was done?

  • drive::document::cost (new, server or verify):
    • document_create_cost(contract, document_type, document, assumptions, platform_version) and document_type_create_cost(.., choices, ..), which first builds a document of chosen sizes (sized_document).
    • The elements an insert writes (cost::writes), built with the functions the walkers use and shaped by drive::document::layout: the document by id (or its revision tree with documentsKeepHistory); per index, the value trees, the [0] terminal and the reference or indexOnly entry; the rows a ranked index keeps in its secondary trees; the trees preallocated for other types' preallocated indexes; a ttl document's entry in the expirations tree. Storage flags follow the walkers: the document's elements carry them, index trees only when documents are mutable or deletable, none for a ttl type.
    • GroveDB's byte formulas (cost::grove_costs), restated because grovedb-merk compiles them only with RocksDB: key bytes, item and layered value bytes, tree cost sizes, and the node feature and link bytes by the tree an element sits in. Tests pin each one to grovedb's own function.
    • Two scenarios: every index value new (the first document with these values creates their trees), and every value known (a later document adds only its own entries; a unique index still adds its value, as do trees keyed by the document's own id and a ttl document's expiration entry, and a ranked row for a known value only moves, which GroveDB bills as replaced bytes).
    • Per index: the bytes of layers shared with other indexes and of its own.
    • Processing: the signature (by key type) and the identity fetch, exact; the writes' work and the checks around the insert, estimated for a number of stored documents; a ttl type's cleanup prepay, exact; the fee increase.
    • Contract charges: the create's action fee (at a fee multiplier), token cost and contest fund (at a number of contenders).
    • Refund: what a delete refunds in the same epoch and a year later (with fee-distribution): the elements it removes that carry the owner's flags, not a ranked tree's rows or the preallocated trees a delete keeps.
    • A ttl type is priced by the lifetime tier (document_ttl_credit_per_byte), with its expiration entry and no refund.
    • Refuses a platform version whose insert, reference, primary storage, index walker or expiration methods differ from protocol version 14's.
    • The storage is an uncontested create's: a value that starts a contest is stored in the vote poll until the contest ends, which is not priced (the contest fund is listed).
  • Shared with the layout: the value helpers the SDK objects are built with (drive::document::sdk_value) and the 19 test contracts (drive::document::fixture_contracts).
  • Shared helpers now compiled for verify as well, unchanged: make_document_reference, make_document_reference_with_sum_item, index_only_member_key (moved from index_only, re-exported there), bound_value_fits_referring_property (moved from the preallocation path), and the expiration module's pricing, paths and DocumentExpirationEntry (its other submodules stay server). document_ttl_pricing now takes its per-byte price from the new document_ttl_credit_per_byte.
  • wasm-sdk: documentCreateCost(contract, documentTypeName, options?, platformVersion) with DocumentCreateCost and DocumentCreateCostOptions TypeScript types: fields (per field, present and length), existingDocuments, signatureKeyType, userFeeIncrease, feeMultiplierPermille, contenders. Unknown option or field keys are refused. evo-sdk re-exports it.
  • Docs: a What a Document Costs page in the book's Fees part, and a What a document costs section in the evo-sdk README.

Before and after

  • Before: what a document of a type costs could only be found by inserting one.
  • After: documentCreateCost(contract, type, undefined, PlatformVersion.latest()) for three bundled examples of the contract visualizer, each variable-size field at its middle size (1 DASH = 100,000,000,000 credits):
Type Stored bytes (new / known values) Total (new / known values) Also
DPNS domain 1,785 / 1,199 53.5M / 38.3M credits (0.00054 DASH) a 0.1 DASH contest fund when the name is contested
Yappr likes tip (indexOnly, ranked, summed) 2,273 / 583 67.4M / 20.1M credits
marketplace listing (ttl, 24 overlapping time windows) 14,980 / 7,437 at 136 credits a byte 26.9M / 30.6M credits a 150,000 credit action fee

For the listing, a later document costs slightly more than the first: its storage is cheap (priced by a month's lifetime), so processing dominates, and writing into existing trees rewrites a node more than creating them.

How Has This Been Tested?

  • cargo test -p drive --lib drive::document::cost: 13 tests.
    • should_price_what_drive_charges: for each of 19 contracts from tests/supporting_files (the ones drive::document::layout is held to), inserts 10 random documents per type, a document repeating the values of the one before, and the SDK's document of middle sizes, with the flags a create uses. Before each insert it reads from GroveDB which trees already exist; after it, each ranked value's aggregate. It requires the estimate to equal the storage fee Drive charged, exactly, for every insert. The first runs found the ranked rows, the rebilling of moved rows and the preallocated trees, which the estimate now models.
    • should_price_a_document_with_a_ttl_by_its_lifetime: the same exact check for a ttl type, plus its cleanup prepay, its expiration entry counted with known values, and no refund.
    • should_price_a_time_window_with_a_ttl_without_flags_as_processing: the references under a ttl'd window carry no flags, and the rest matches a real insert exactly.
    • should_count_trees_keyed_by_the_document_id_as_new_and_unrefunded: a Yappr post's preallocated trees keyed by its id count with known values and are not refunded.
    • should_estimate_the_processing_of_the_writes_within_a_factor_of_two: the writes' processing estimate against Drive's processing fee after 1, 10 and 100 documents in six contracts; a failed insert fails the test.
    • should_split_the_storage_into_primary_storage_and_each_index, should_add_the_contract_charges (an action fee, the DPNS contest fund), should_charge_a_later_document_with_known_values_no_more_than_the_first (every type of the 19 contracts), should_refuse_an_earlier_protocol_version.
    • Four grove_costs tests pin the restated formulas to grovedb's KV functions, TreeType::inner_node_type and Element::specialized_costs_for_key_value, for every tree type.
  • cargo test -p drive --lib: all pass.
  • cargo clippy -p drive --all-targets, cargo clippy -p drive --no-default-features --features verify, cargo clippy -p wasm-sdk --target wasm32-unknown-unknown, cargo fmt --all -- --check: clean.
  • yarn workspace @dashevo/wasm-sdk build, then mocha tests/unit/document-create-cost.spec.ts: 6 passing (middle sizes, the index split, field lengths and presence, the action fee and processing by key type, a ttl type, unknown keys refused); eslint clean.
  • Not run locally: the Karma browser run of the wasm-sdk spec.

Breaking Changes

None.

Checklist:

  • I have performed a self-review of my own code
  • I have commented my code, particularly in hard-to-understand areas
  • I have added or updated relevant unit/integration/functional/e2e tests
  • I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
  • I have made corresponding changes to the documentation if needed
  • If I added or changed GroveDB structure, I described it in the area's structure.rs, regenerated grovedb-structure.json, and checked the structure viewer link posted on this pull request

For repository code-owners and collaborators only

  • I have assigned this pull request to a milestone

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PR Hygiene · 51f666e

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    • js-wasm-sdk (packages/js-evo-sdk/README.md, packages/wasm-sdk/Cargo.toml, packages/wasm-sdk/src/document_create_cost.rs and 2 more) — shumkov
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Summary by CodeRabbit

  • New Features
    • Added a JavaScript SDK API to estimate document creation costs without network access. Estimates include storage and processing costs, index details, contract charges, and applicable refunds, with options for field sizes and pricing assumptions.
    • Added documentation explaining cost estimates, TTL pricing, and supported protocol versions.

`drive::document::cost` prices a document create from the contract alone:
the storage of every element the insert writes (exact: the elements the
walkers build, priced with GroveDB's byte formulas, including a ranked
index's secondary rows, preallocated trees and a ttl document's
expiration entry), split by index into shared and own layers, under two
scenarios (every index value new, every value already stored); the
processing (the signature and identity fetch exact, the writes
estimated for a number of stored documents, a ttl type's cleanup
prepay); the contract's action fee, token cost and contest fund; and
what a delete refunds. A document can be built from sizes rather than
values (`sized_document`).

wasm-sdk exposes it as `documentCreateCost(contract, documentTypeName,
options, platformVersion)`, building rs-drive with `fee-distribution`
for the refund.

Shared helpers now also compile for `verify`, unchanged: the document
reference builders, `index_only_member_key` and
`bound_value_fits_referring_property` (moved), and the expiration
module's pricing, paths and entry; `document_ttl_pricing` takes its
per-byte price from the new `document_ttl_credit_per_byte`.

A test requires the storage to equal what Drive charges on real inserts
into 19 contracts, byte for byte.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
@github-actions github-actions Bot added this to the v4.2.0 milestone Sep 28, 2026
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📖 Book Preview built successfully.

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To view locally: download the artifact, unzip, and open index.html.

Updated at 2026-09-28T22:54:59.608Z

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Review in Change Stack →

Navigate logical layers of code changes, visualize relationships, and explore their blast radius.

📝 Walkthrough

Walkthrough

Adds a Drive document-creation cost estimator and a WASM/JavaScript documentCreateCost API. The estimate models document and index writes, storage and processing credits, contract charges, refunds, and TTL pricing across new-value and known-value scenarios. The PR also adds tests and documentation.

Changes

Document Creation Cost Estimation

Layer / File(s) Summary
Build document sizes and priced writes
packages/rs-drive/src/drive/document/cost/document.rs, packages/rs-drive/src/drive/document/cost/writes.rs, packages/rs-drive/src/drive/document/cost/grove_costs.rs, packages/rs-drive/src/drive/document/mod.rs, packages/rs-drive/src/drive/document/layout.rs, packages/rs-drive/src/drive/document/index_only.rs, packages/rs-drive/src/drive/document/insert/add_preallocated_index_tree_operations/mod.rs, packages/rs-drive/src/drive/document/expiration/*
Adds field-sized document construction and models primary, index, preallocated-index, ranked-row, and TTL expiration writes. Adds GroveDB element byte calculations and supporting document helpers.
Calculate cost scenarios and validate estimates
packages/rs-drive/src/drive/document/cost/mod.rs, packages/rs-drive/src/drive/document/cost/tests.rs, book/src/fees/document-cost.md, book/src/SUMMARY.md
Calculates storage and processing scenarios, contract charges, refunds, and TTL costs. Tests compare modeled costs with Drive charges and check index sharing, protocol-version handling, and TTL pricing. Adds the book page and Fees navigation link.
Expose and document the JavaScript API
packages/wasm-sdk/src/document_create_cost.rs, packages/wasm-sdk/src/lib.rs, packages/wasm-sdk/Cargo.toml, packages/wasm-sdk/tests/unit/document-create-cost.spec.ts, packages/js-evo-sdk/README.md
Adds the WASM documentCreateCost API, its options and result types, input validation, and unit tests. Documents the API and its estimate fields in the JavaScript SDK README.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant JavaScriptCaller as JavaScript caller
  participant documentCreateCost
  participant document_type_create_cost
  participant DocumentCreateCostJs
  JavaScriptCaller->>documentCreateCost: contract, document type, options, platform version
  documentCreateCost->>document_type_create_cost: field choices and cost assumptions
  document_type_create_cost-->>documentCreateCost: document cost estimate
  documentCreateCost-->>DocumentCreateCostJs: serialized WASM result
  DocumentCreateCostJs-->>JavaScriptCaller: cost scenarios and breakdown
Loading

Suggested reviewers: shumkov

Merge Risk: 🔵 Low · up to 1973b

The new document-cost estimate may overstate deletion refunds for document types with ranked indexes. Actual fees are unaffected, so this can merge with a follow-up, though fixing it first would make the reported refunds accurate.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 1973b

The new API calculates and returns estimates; the reviewed path does not submit documents or set the fees charged for them. Its main design risk is that callers may rely on estimates whose processing and conditional charges depend on assumptions. No material security issue was established, but review coverage is incomplete.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

  • inferred — The reviewed public path exposes estimate computation to SDK callers, but does not itself give them authority over node state, another tenant’s data, or charged fees. Downstream applications may nevertheless act on the returned estimate.

Trust Boundaries and Controls

  • observed — Untrusted JavaScript options cross into Drive as typed assumptions and field choices after SDK validation. The reviewed Drive function takes no persistence or authorization context and returns an estimate.

Resilience and Maintainability Implications

  • inferred — Because assumptions affect the returned calculation rather than authoritative insertion fees, an inaccurate assumption primarily risks a misleading client-side estimate. This assessment does not establish how every downstream consumer uses the result.
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❌ Failed checks (1 warning)

Check name Status Explanation Resolution
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Check name Status Explanation
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.
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly describes the main change: adding document-creation cost estimation for the SDKs. It is concise and specific.
Full details: Docstring Coverage

Explanation

Docstring coverage is 77.08% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 96 functions across 14 files. (4 skipped: 4 unsupported.)

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thepastaclaw commented Sep 28, 2026 •

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🔍 Review in progress — actively reviewing now (commit 51f666e) · triage: normal

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Actionable comments posted: 1


  • 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @packages/rs-drive/src/drive/document/cost/mod.rs:
- Around line 489-495: Update the `PricedElement::Serialized` case in
`refundable_bytes` so ranking rows are excluded from refundable storage, using
`write.ranking` to identify them instead of relying only on `write.ephemeral`.

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Reviewing files that changed from the base of the PR and between 99bc968 and 1973b77.

📒 Files selected for processing (18)
  • book/src/SUMMARY.md
  • book/src/fees/document-cost.md
  • packages/js-evo-sdk/README.md
  • packages/rs-drive/src/drive/document/cost/document.rs
  • packages/rs-drive/src/drive/document/cost/grove_costs.rs
  • packages/rs-drive/src/drive/document/cost/mod.rs
  • packages/rs-drive/src/drive/document/cost/tests.rs
  • packages/rs-drive/src/drive/document/cost/writes.rs
  • packages/rs-drive/src/drive/document/expiration/mod.rs
  • packages/rs-drive/src/drive/document/expiration/pricing.rs
  • packages/rs-drive/src/drive/document/index_only.rs
  • packages/rs-drive/src/drive/document/insert/add_preallocated_index_tree_operations/mod.rs
  • packages/rs-drive/src/drive/document/layout.rs
  • packages/rs-drive/src/drive/document/mod.rs
  • packages/wasm-sdk/Cargo.toml
  • packages/wasm-sdk/src/document_create_cost.rs
  • packages/wasm-sdk/src/lib.rs
  • packages/wasm-sdk/tests/unit/document-create-cost.spec.ts

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Comment thread packages/rs-drive/src/drive/document/cost/mod.rs Outdated
…t a delete refunds

Review fixes for the document cost estimate:
- The known-values scenario counts as new every tree keyed by the
  document's own id (a preallocated index's) with what is under it, and a
  ttl document's expiration entry.
- The refund counts only elements carrying the owner's flags that a
  delete removes: not a ranked tree's rows, preallocated trees (kept on
  delete) or flagless items (each write now records its flags).
- References under a time window with a ttl carry no flags, as Drive
  strips them; a new test covers such a window against a real insert.
- The estimate refuses a platform version whose insert, reference,
  primary storage or expiration methods differ from those it mirrors, not
  only the index walkers.
- The known-values processing counts a ranked row's move.
- Transient fields are neither priced nor listed in `fields`.
- The documentation says the storage is an uncontested create's (a
  contested value is stored in the vote poll, not priced) and when index
  trees carry flags.
- Cleanups: the SDK value helpers and the 19 test contracts are shared
  with the layout (`sdk_value`, `fixture_contracts`); the document is
  serialized once; writes are deduplicated with a set; `platform_version`
  last in `fill`; no inline `crate::` paths; the processing test no longer
  skips failed inserts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Approved

@QuantumExplorer
QuantumExplorer merged commit fcacc64 into v4.2-dev Sep 28, 2026
36 of 38 checks passed
@QuantumExplorer
QuantumExplorer deleted the feat/drive-document-cost-estimate branch September 28, 2026 23:33
PastaPastaPasta added a commit that referenced this pull request Sep 28, 2026
Pick up #5159 (compute what creating a document costs for the SDKs).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
@PastaPastaPasta PastaPastaPasta mentioned this pull request Sep 28, 2026
2 of 24 tasks
QuantumExplorer added a commit to dashpay/contract-visualizer that referenced this pull request Sep 29, 2026
* docs: say what the example check runs: the parser, not the meta-schema

@dashevo/evo-sdk is built without dpp's validation feature, so
DataContract.fromJSON(json, true, 14) runs the contract parser but not the
document meta-schema or the parser checks gated behind that feature. The
README, the examples registry and the validation script claimed more.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* feat: show a document type's GroveDB layout, computed by Drive

A "GroveDB layout" button in the inspector opens every tree and element
Drive writes for the selected document type: the documents by id (and
revisions), and for each index the property and value trees down to the
[0] where it ends, with each layer's element (count, sum, ranked, ...),
its zero-contribution wrapper, the indexes that use it, conditions (the
null fallback of a unique index, skipIfAbsent, preallocated, time window
overlap) and a link to that kind of layer in the GroveDB structure viewer.

The layout comes from documentTypeLayout in @dashevo/evo-sdk
(dashpay/platform#5153), so it follows Drive's own rules. It is
feature-detected: with an SDK that predates it, the panel says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: refresh the layout fixtures from the merged documentTypeLayout

dashpay/platform#5153 merged with a review fix: a unique index's null
fallback no longer repeats the terminal's indexes and notes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* feat: show what a document costs, in Dash and dollars, per index

Selecting a document type shows about what one of its documents costs;
Cost opens the breakdown, computed by Drive (documentCreateCost in
@dashevo/evo-sdk, dashpay/platform#5159): the first document with a set
of index values and a later one with the same values; the storage of
the document itself and of each index on its own (the part it shares
with other indexes, paid once, and its own); prepaid trees and a ttl
type's expiration entry; the processing (exact parts marked, the rest
estimated for a number of stored documents, a key type and a fee
increase); the contract's action fee, token cost and contest fund; and
the refund on delete. "Adjust the document" gives an on/off switch per
optional field and a length per variable-size one; fixed-size fields
need no input.

The Dash price comes from CoinGecko (Coinbase if that fails), kept five
minutes, and can be typed in. Feature-detected: with an SDK that
predates documentCreateCost the inspector says so. The layout and cost
loaders share one local SDK module.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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