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ProbeLabs23 findings · 123 requirementsThe fastest JSON parser for Go — formally verified with ReqProof (real library, master).
When Set targets an array-index path component [N] where N >= the current length of the addressed array, the parser shall append the value at the end of the array (index becomes len(array)) and return the mutated document, rather than overwriting existing elements or panicking.
Specification
The requirement exactly as authored — its complete prose text and, where present, the formal FRETish sentence it compiles to.
When Set targets an array-index path component [N] where N >= the current length of the addressed array, the parser shall append the value at the end of the array (index becomes len(array)) and return the mutated document, rather than overwriting existing elements or panicking. This contract applies regardless of the existing array's element types (scalars, objects, nested arrays, mixed); the previous implementation only honored it when the first element was an object, silently replacing scalar arrays — fixed (DEFECT-260727-WWWY).
the parser shall always satisfy !set_targets_array_index_beyond_length | set_appends_value_at_array_end
Rationale & tags
Why this requirement exists, and how it is categorised.
Rationale & tags
Why this requirement exists, and how it is categorised.
Set on an array-index beyond current length was underspecified; PR #286 found it silently overwrites element 0, destroying data the caller did not address. The append-at-end contract must be explicit so the overwrite path can never regress.
Verification & provenance
How this requirement was checked: the review trail, edit history, and the machine-analysis status terms (each ⓘ explains what it means).
Review
- Status
- approved
- Reviewer
- Buger · lead_engineer
- Reviewed
- Jul 27, 2026, 06:53 UTC
History
- Created
- Jul 26, 2026, 17:12 UTC · Created via CLI
- Modified
- Jul 27, 2026, 06:53 UTC · Buger
Change history
Every recorded revision of this requirement's source file — newest first, each with its commit message and the diff for that change.
Every recorded revision of this object's source — newest first, each with the commit message and its file-level diff.
Obligations
What this requirement must witness to be considered satisfied — the required evidence, and the tests that discharge each one.
3 obligations · 2 discharged · 1 delegated
Browse the catalogueBehavior at limits, thresholds, and edge-of-range values.
Set on [len(array)] or beyond silently overwrites element 0 (or another existing element the caller did not address), destroying data and returning a mutated document with no error — silent corruption of unaddressed state.
SYS-REQ-110 is a leaf contract partition; the boundary implementation lives in parser.go:Set / parser.go:createInsertComponent which SYS-REQ-009 already carries implemented_by traces for (source_native autolink). Delegating avoids weakening SYS-REQ-110 by removing the obligation.
- nominalrequiredpresentCovered by 1 test
- negativerecommendedpresentCovered by 1 test
Set on a beyond-length array index inside a nested container drives createInsertComponent to emit array scaffolding at the wrong offset; a regression overwrites a sibling element or builds malformed JSON, silently corrupting the nested structure.
- nominalrequiredpresentCovered by 1 test
Set on a beyond-length array index under a nested key whose existing array contains SCALAR first elements (numbers, strings, bools, nulls, nested arrays — anything where the first element byte is not '{') silently replaces the entire array with a single-element [value], destroying all existing data. The append-at-end code path's guard previously required data[subObjOff]=='{' , so only object-first-element arrays took the append branch; scalar arrays fell through to the replace-container branch. Fixed in DEFECT-260727-WWWY; regression test TestSetBeyondLengthScalarArrayPreservesElements_SYS110 locks all scalar element-type partitions.
- nominalrequiredpresentCovered by 1 test
Formula evidence
The formal formula behind this requirement, the variables it is written over, and the tests that exercise it (each term is explained inline).
Formula evidence
The formal formula behind this requirement, the variables it is written over, and the tests that exercise it (each term is explained inline).
FRETish formula
the parser shall always satisfy !set_targets_array_index_beyond_length | set_appends_value_at_array_end
Variables
| Name | Type | Direction | Description |
|---|---|---|---|
| set_targets_array_index_beyond_length | — | True when Set addresses an array-index path component [N] where N >= the current length of the addressed array (the beyond-length partition of array_index). | |
| set_appends_value_at_array_end | — | True when Set appends the value at the end of the addressed array (the new element's index becomes len(array)) and returns the mutated document, rather than overwriting an existing element or panicking. |
Witnesses· 3 scenarios total
- TestMCDC_SYS_REQ_110_Row1_InRangeNoAppendexercises 1 condition scenario
- TestMCDC_SYS_REQ_110_Row2_InvariantViolationexercises 1 condition scenario
- TestMCDC_SYS_REQ_110_Row3_BeyondLengthAppendsAtEndexercises 1 condition scenario
MC/DC truth table· 3 rows
Each row assigns the formula's conditions (T/F) and shows the Result— the formula's value for that input row, not a test pass/fail. A row proves a condition when flipping only that condition flips the outcome. The test that covers each row is linked.
mcdc:ignoreNo-actionfalse-result row satisfied by designUncoveredneeds a covering test| # | set_appends_value_at_array_end | set_targets_array_index_beyond_length | Result | Proves | Covering test |
|---|---|---|---|---|---|
| 1 | F | F | T | set_targets_array_index_beyond_length | |
| 2 | F | T | F | set_appends_value_at_array_end | |
| 3 | T | T | T | set_appends_value_at_array_end |
Its place
This requirement shown inside its trace neighbourhood — the parents it satisfies, the code and tests attached to it, and its findings.
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Trace evidence
The concrete artifacts linked to this requirement — implementing code, verifying tests, documents, and the findings raised against it.
Impact
Blast radius — if you change this requirement, what else may need re-checking, and what it in turn depends on.
Impact
Blast radius — if you change this requirement, what else may need re-checking, and what it in turn depends on.
If you change this
Files to re-check (2)
- append.goappend.go
- parser.goparser.go
Tests to re-run (7)
- append_test.goappend_test.go
- fuzz_native_test.gofuzz_native_test.go
- mcdc_supplement_test.gomcdc_supplement_test.go
- parser_test.goparser_test.go
- reference_oracle_test.goreference_oracle_test.go
- set_spec_test.goset_spec_test.go
- sys_req_110_111_witness_test.gosys_req_110_111_witness_test.go
What this rests on
Parent requirements (1)
Changes
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Discussions
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