✨ Align QsNet with qs 6.16 and add encoder depth limits

[techouse]

Description

Upgrade the Node comparison oracle to qs 6.16.0 and port the relevant behavior to QsNet:

• Enforce strict ListLimit for comma groups under bracket-push keys and spread later comma groups over consecutive numeric keys after overflow.
• Encode literal dots in top-level scalar keys when EncodeDotInKeys is enabled.
• Add optional EncodeOptions.Depth (unlimited by default), throwing when a finite limit is exceeded. Add CopyWithDepth to configure it without changing the existing CopyWith signature.
• Release the encoder's active-container tracking when a depth limit aborts an encode, so retrying with the same internal side channel does not report a false cycle.

Type of change

• Bug fix
• New feature
• Documentation update

How Has This Been Tested?

• dotnet test — 1,115 tests passed.
• dotnet test tests/QsNet.Tests/QsNet.Tests.csproj --filter FullyQualifiedName~ShouldReleaseTrackedAncestorsAfterEncodeDepthFailure — regression test passed.
• dotnet build src/QsNet/QsNet.csproj — both targets built with zero warnings or errors.

Checklist

• Self-reviewed the changes.
• Updated documentation.
• Added regression tests and passed the test suite.

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📝 Walkthrough

Walkthrough

The decoder changes comma-group limit checks and overflow-map merging. The encoder adds an optional depth limit and escapes dots in top-level keys when configured.

Changes

Decoder list handling

Layer / File(s)	Summary
Enforce comma-group limits src/QsNet/Internal/Decoder.cs, tests/QsNet.Tests/DecodeTests.cs, README.md, docs/index.md, CHANGELOG.md	The decoder now checks the comma-count limit for bracket-array values when strict limits are enabled. Tests and documentation describe rejection and lenient preservation.
Spread values into overflow maps src/QsNet/Internal/Utils.cs, tests/QsNet.Tests/DecodeTests.cs, tests/QsNet.Tests/UtilsTests.cs	Enumerable inputs are appended across successive numeric keys when the target is an overflow map. Tests cover comma groups, empty inputs, nested lists, and subsequent values.

Encoding depth limits

Layer / File(s)	Summary
Configure and enforce encoding depth src/QsNet/Models/EncodeOptions.cs, src/QsNet/Internal/EncodeFrame.cs, src/QsNet/Internal/Encoder.cs, tests/QsNet.Tests/EncodeOptionsTests.cs, tests/QsNet.Tests/EncodeTests.cs, README.md, docs/index.md	EncodeOptions adds nullable Depth and CopyWithDepth. The encoder tracks frame depth and throws when it exceeds a finite limit. Tests and documentation cover the option and limit behavior.

Top-level dotted keys

Layer / File(s)	Summary
Escape top-level dots src/QsNet/Internal/KeyPathNode.cs, src/QsNet/Qs.cs, tests/QsNet.Tests/EncodeTests.cs, README.md, tests/QsNet.Comparison/js/package.json	When enabled, EncodeDotInKeys dot-escapes top-level keys before encoding. Function filters receive the escaped prefix. The comparison setup updates its qs dependency to 6.16.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Qs
  participant Encoder
  participant EncodeFrame
  Qs->>Encoder: Encode with configured depth
  Encoder->>EncodeFrame: Create root frame at depth 0
  Encoder->>EncodeFrame: Create child frame at incremented depth
  Encoder->>Encoder: Throw if current depth exceeds maximum

Loading

Merge Risk: 🔵 Low · up to 766b7

Encoding through the public API is unaffected by this state leak. Internal callers that reuse a side channel can encounter a false cycle error after a depth-limit failure; clean up the frame before merging or accept this bounded risk.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 766b7

Encoding a dotted top-level key can now change the key name seen by an application’s filter. Applications that use that name to redact values may need to update their filter; no affected application or confirmed data exposure was identified.

Retained concerns

• Medium · security · inferred: With EncodeDotInKeys enabled, a dotted top-level key is escaped before its value reaches FunctionFilter. A consumer filter that redacts by matching the previously raw prefix may no longer match and may serialize the original value.

Security review details

Security Blast Radius

• inferred — The potential redaction failure is limited to consumers using EncodeDotInKeys and a path-sensitive per-value filter, and to values encoded by those calls. No tenant boundary, privileged sink, or affected downstream application was established.

Security Findings and Attack Paths

• inferred — If an attacker can supply a dotted top-level key and value, and a consumer redacts that value by matching the formerly raw FunctionFilter prefix, the escaped prefix can miss the match and leave the value in the query string. This is a conditional consumer attack path, not a verified exposure.

Trust Boundaries and Controls

• observed — Strict decoder comma-group rejection occurs before duplicate-value merging. The inspected lenient merge path appends elements in order and maintains overflow index metadata through repeated merges.

Resilience and Maintainability Implications

• inferred — Depth is a nesting control rather than a total-work limit. Applications accepting attacker-supplied enumerables cannot rely on Depth alone to bound enumeration work; this is not a bypass of the stated depth contract.

Hardening Proposals

• proposed — Keep filter callbacks on a clearly specified raw-key path, or explicitly document the escaped-prefix contract and test migration of path-based redaction filters.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 18.18% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 33 functions across 11 files. (4 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

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.
Title check	✅ Passed	The title clearly identifies the two primary changes: alignment with qs 6.16 and encoder depth limits.
Description check	✅ Passed	The description includes the change summary, change types, testing details, and checklist confirmations. It does not specify an issue number and omits some template checklist items, but it is otherwis…

Full details: Docstring Coverage

Explanation

Docstring coverage is 18.18% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 33 functions across 11 files. (4 skipped: 4 unsupported.)

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[codacy-production]

Not up to standards ⛔

🔴 Issues 3 medium

Alerts:
⚠ 3 issues (≤ 0 issues of at least minor severity)

Results:
3 new issues

Category	Results
Complexity	3 medium

View in Codacy

🟢 Metrics 4 complexity · 2 duplication

Metric	Results
Complexity	4
Duplication	2

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.14%. Comparing base (5935066) to head (57e1a09).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #130      +/-   ##
==========================================
+ Coverage   99.12%   99.14%   +0.02%     
==========================================
  Files          20       20              
  Lines        2160     2229      +69     
  Branches      543      548       +5     
==========================================
+ Hits         2141     2210      +69     
  Misses         19       19              

Flag	Coverage Δ
unittests	99.14% <100.00%> (+0.02%)	⬆️

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Actionable comments posted: 1

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @src/QsNet/Internal/Encoder.cs:
- Around line 157-159: Update Encoder.Encode so a MaxDepth violation unwinds all
tracked ancestor containers from SideChannelFrame before propagating the
existing depth exception. Preserve normal FinishFrame behavior and leave the
depth-limit condition unchanged.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: e1801ebf-3a4a-4fbd-909d-12a329ac121c

📥 Commits

Reviewing files that changed from the base of the PR and between 5935066 and 766b71a.

⛔ Files ignored due to path filters (1)

• tests/QsNet.Comparison/js/pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (15)

• CHANGELOG.md
• README.md
• docs/index.md
• src/QsNet/Internal/Decoder.cs
• src/QsNet/Internal/EncodeFrame.cs
• src/QsNet/Internal/Encoder.cs
• src/QsNet/Internal/KeyPathNode.cs
• src/QsNet/Internal/Utils.cs
• src/QsNet/Models/EncodeOptions.cs
• src/QsNet/Qs.cs
• tests/QsNet.Comparison/js/package.json
• tests/QsNet.Tests/DecodeTests.cs
• tests/QsNet.Tests/EncodeOptionsTests.cs
• tests/QsNet.Tests/EncodeTests.cs
• tests/QsNet.Tests/UtilsTests.cs

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