Deep: High-Performance Data Manipulation for Go

deep is a high-performance, reflection-based engine for manipulating complex Go data structures. It provides recursive deep copying, semantic equality checks, and structural diffing to produce optimized patches.

V4 focuses on API ergonomics with a fluent patch builder and advanced conflict resolution for distributed systems.

Installation

go get github.com/brunoga/deep/v4

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Core Features

1. Deep Copy

Justification: Standard assignment in Go performing shallow copies. deep.Copy creates a completely decoupled clone, correctly handling pointers, slices, maps, and private fields (via unsafe).

dst, err := deep.Copy(src)

• Recursive: Clones the entire object graph.
• Cycle Detection: Safely handles self-referencing structures.
• Unexported Fields: Optionally clones private struct fields.
• Example: Config Management

2. Semantic Equality (Equal[T])

Justification: reflect.DeepEqual is slow and lacks control. deep.Equal is a tag-aware, cache-optimized replacement that is up to 30% faster and respects library-specific struct tags.

if deep.Equal(objA, objB) {
    // Logically equal, respecting deep:"-" tags
}

• Tag Awareness: Skips fields marked with deep:"-".
• Short-Circuiting: Immediately returns true for identical pointer addresses.
• Performance: Uses a global reflection cache to minimize lookup overhead.

3. Structural Diff & Patch

Justification: Efficiently synchronizing state between nodes or auditing changes requires knowing what changed, not just that something changed. deep.Diff produces a semantic Patch representing the minimum set of operations to transform one value into another.

// Generate patch
patch, err := deep.Diff(oldState, newState)

// Inspect changes
fmt.Println(patch.Summary()) 

// Apply to target
err := patch.ApplyChecked(&oldState)

• Move & Copy Detection: Identifies relocated values to minimize patch size.
• Three-Way Merge: Merges independent patches with conflict detection.
• JSON Standard: Native export to RFC 6902 (JSON Patch).
• Examples: Move Detection, Three-Way Merge

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Advanced Capabilities

Fluent Patch Builder

V4 introduces a fluent API for manual patch construction, allowing for intuitive navigation and modification of data structures without manual path management.

builder := deep.NewPatchBuilder[MyStruct]()
builder.Field("Profile").Field("Age").Set(30, 31)
builder.Field("Tags").Add(0, "new-tag")
patch, err := builder.Build()

Advanced Conflict Resolution

For distributed systems and CRDTs, deep allows you to intercept and resolve conflicts dynamically. The resolver has access to both the current value at the target path and the proposed value.

type MyResolver struct{}

func (r *MyResolver) Resolve(path string, op deep.OpKind, key, prevKey any, current, proposed reflect.Value) (reflect.Value, bool) {
    // Custom logic: e.g., semantic 3-way merge or timestamp-based LWW
    return proposed, true 
}

err := patch.ApplyResolved(&state, &MyResolver{})

Struct Tag Control

Fine-grained control over library behavior:

• deep:"-": Completely ignore field.
• deep:"key": Identity field for slice alignment (Myers' Diff).
• deep:"readonly": Field can be diffed but not modified by patches.
• deep:"atomic": Treat complex fields as scalar values.

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Performance Optimization

Built for performance-critical hot paths:

• Zero-Allocation Engine: Uses sync.Pool for internal transient structures during diffing.
• Reflection Cache: Global cache for type metadata to eliminate repetitive lookups.
• Lazy Allocation: Maps and slices in patches are only allocated if changes are found.

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Version History

v4.0.0: Ergonomics & Context (Current)

• Fluent Patch Builder: Merged Node into PatchBuilder for a cleaner, chainable API.
• Context-Aware Resolution: ConflictResolver now receives both current and proposed values and can return a merged result.
• Strict JSON Pointers: Removed dot-notation support in favor of strict RFC 6901 compliance.
• Simplified Registry: Global RegisterCustom* functions for easier extension.

v3.0.0: High-Performance Engine

• Zero-Allocation Engine: Refactored to use object pooling.
• deep.Equal[T]: High-performance, tag-aware replacement for reflect.DeepEqual.
• Move & Copy Detection: Semantic detection of relocated values during Diff.

v2.0.0: Synchronization & Standards

• JSON Pointer (RFC 6901): Standardized path navigation.
• Keyed Slice Alignment: Integrated identity-based matching into Myers' Diff.
• HLC & CRDT: Introduced Hybrid Logical Clocks and LWW conflict resolution.

v1.0.0: The Foundation

• Initial recursive Deep Copy and Deep Diff implementation.

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License

Apache 2.0