Cherry-pick: Implement global deep_equals function

[JoltedJon]

Brings in godotengine/godot#105632

Summary by CodeRabbit

• New Features
  • Added deep_equals(a, b) to compare values recursively. Arrays are compared by size and contents, dictionaries without regard to key order, and objects by their properties. Other value types use standard equality.
• Documentation
  • Documented the new comparison function and its behavior.

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Reviewing files that changed from the base of the PR and between 04bddf6 and a1df938.

📒 Files selected for processing (2)

• core/variant/variant_utility.cpp
• tests/core/variant/test_variant_utility.h

🚧 Files skipped from review as they are similar to previous changes (2)

• tests/core/variant/test_variant_utility.h
• core/variant/variant_utility.cpp

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Walkthrough

The change adds and documents deep_equals, a Variant utility that compares basic values with ordinary equality and recursively compares arrays, dictionaries, and objects. Tests cover matching and differing values, nested containers, circular references, and recursion-depth exhaustion.

Changes

Variant Equality

Layer / File(s)	Summary
Recursive comparison core/variant/variant_utility.h, core/variant/variant_utility.cpp	Adds the public deep_equals method and recursive comparisons for arrays, dictionaries, and objects. Other Variant types use ordinary equality.
Utility exposure and validation core/variant/variant_utility.cpp, doc/classes/@GlobalScope.xml, tests/core/variant/test_variant_utility.h	Registers and documents deep_equals. Tests cover basic values, object properties and metadata, nested containers, circular references, and recursion-depth exhaustion.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Suggested reviewers: mcdubhghlas, arctis-fireblight

Merge Risk: ⚪ Minimal · up to a1df9

The recursive equality implementation and its public interface are consistent, with coverage for cyclic containers and recursion limits. No actionable merge-blocking risk was identified; merge after normal build and test checks.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 04bdd

Recursive equality can perform excessive work on small cyclic inputs and report unequal deep values as equal. The demonstrated effects concern the calling process; remote exposure, privilege escalation, and security-sensitive uses have not been established.

Retained concerns

• Medium · security · inferred: The new public comparator bounds recursion depth but not total work. An array containing two references to itself, compared even with itself, revisits both branches at every level, producing exponential traversal toward depth 100. There is no visited-pair tracking or container-identity shortcut. Existing container equality returns immediately for identical backing storage, so this introduces a materially more expensive comparison path. Caller-controlled cyclic values can monopolize the calling process when routed through this API; no remote delivery path or host execution quota was established.
• Medium · architecture · observed: The documented content-equality contract treats recursion exhaustion as successful equality: the guard returns true before checking the remaining values or their types. Consequently, finite unequal structures whose difference lies beyond the limit can compare equal, without a distinct indeterminate result. Similar depth-exhaustion behavior already exists in container equality helpers, but the PR exposes it through a new general structural API. No consumer using this result for authorization or another security decision was established.

Security review details

Security Blast Radius

• inferred — The supported attackable scope is execution in a process that compares caller-controlled cyclic or shared containers through the new utility. Excessive synchronous traversal can consume that process's execution time. The inspected evidence does not establish cross-tenant, service-wide, remote, or privileged exposure.

Security Findings and Attack Paths

• inferred — A caller able to supply a self-referential array with two recursive elements can trigger repeated traversal without constructing a large container. Both branches continue until the depth guard returns true, so the guard does not provide a practical work bound. This is a source-derived availability concern, not an executed exploit or a verified remote attack path.

Trust Boundaries and Controls

• observed — Object comparison operates on handles already supplied by the caller and delegates reads to established script, extension, and built-in getter paths. No new authority-acquisition mechanism was observed. These callbacks remain relevant to ordering and consistency, but no concrete mutating or reentrant getter was shown to cause an ownership violation.

Hardening Proposals

• proposed — Define explicit cycle and depth-exhaustion semantics, track comparison pairs, and enforce a total-work budget rather than relying solely on depth. Preserve safe container-identity shortcuts and distinguish inability to complete comparison from established equality. Document that object comparison invokes getters rather than reading an immutable snapshot.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main change: implementing the global deep_equals function. The cherry-pick context also matches the stated pull request objective.
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.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @core/variant/variant_utility.cpp:
- Around line 1234-1237: Update `_deep_equals` to track active identity pairs
for Arrays, Dictionaries, and Object pointers, treating a pair already being
compared as equal to support cyclic comparisons and removing pairs when each
comparison completes. Return false when the recursion depth limit is reached
instead of accepting unequal values without comparison, and update the
circular-reference tests to verify cycle handling without relying on depth
exhaustion.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository: Redot-Engine/redot-engine/.coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: ea27c345-5674-457d-b4a7-f1f5a78d7da2

📥 Commits

Reviewing files that changed from the base of the PR and between 80d31f7 and 04bddf6.

📒 Files selected for processing (4)

• core/variant/variant_utility.cpp
• core/variant/variant_utility.h
• doc/classes/@GlobalScope.xml
• tests/core/variant/test_variant_utility.h

Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 6 remain after this review.