feat: Multi-Context Support for EFCore Adapter

[thoraj]

Multi-Context Support for EFCore Adapter

Summary

This PR adds multi-context support to the EFCore adapter, enabling different Casbin policy types to be stored in separate database locations (schemas, tables, or databases) while maintaining transactional integrity and full backward compatibility.

Motivation

Organizations often need to separate policy data for various reasons:

• Multi-tenancy: Isolate tenant data in separate schemas
• Compliance: Separate sensitive role assignments from general policies
• Performance: Distribute data across different databases or table partitions

Key Features

1. Multi-Context Architecture

• ICasbinDbContextProvider<TKey> interface: Routes policy types (p, p2, g, g2, etc.) to appropriate DbContext instances
• Per-context schema/table control: Each context independently controls both schemaName and tableName
• Flexible routing: Developers implement routing logic based on their requirements

2. Transaction Integrity

• Atomic operations: When contexts share a DbConnection, all changes commit atomically or rollback together
• Shared connection support: PostgreSQL, MySQL, SQL Server, SQLite (same file)
• EnableAutoSave integration: Disable AutoSave for batched atomic commits across contexts

3. Backward Compatibility

• Zero breaking changes: Existing single-context usage works unchanged
• SingleContextProvider<TKey>: Default provider maintains current behavior
• All existing tests passing: 186 unit tests + 114 integration tests = 300 tests across all frameworks

Implementation Details

New Types

ICasbinDbContextProvider

public interface ICasbinDbContextProvider<TKey> where TKey : IEquatable<TKey>
{
    DbContext GetContextForPolicyType(string policyType);
    IEnumerable<DbContext> GetAllContexts();
    DbConnection? GetSharedConnection();
}

SingleContextProvider (default, backward-compatible)

• Wraps single DbContext
• Returns same context for all policy types

Example: Policy/Grouping Separation

// Create shared connection for atomic transactions
var sharedConnection = new SqlConnection(connectionString);

// Create contexts with different schemas
var policyContext = new CasbinDbContext<int>(
    new DbContextOptionsBuilder<CasbinDbContext<int>>()
        .UseSqlServer(sharedConnection).Options,
    schemaName: "policies",
    tableName: "casbin_rule");

var groupingContext = new CasbinDbContext<int>(
    new DbContextOptionsBuilder<CasbinDbContext<int>>()
        .UseSqlServer(sharedConnection).Options,
    schemaName: "groupings",
    tableName: "casbin_rule");

// Implement provider
public class PolicyTypeContextProvider : ICasbinDbContextProvider<int>
{
    public DbContext GetContextForPolicyType(string policyType)
    {
        return policyType.StartsWith("p") ? _policyContext : _groupingContext;
    }

    public DbConnection? GetSharedConnection() => _sharedConnection;
}

// Use with adapter
var adapter = new EFCoreAdapter<int>(provider);
var enforcer = new Enforcer("model.conf", adapter);
enforcer.EnableAutoSave(false);

// All operations work transparently
enforcer.AddPolicy("alice", "data1", "read");      // → policies schema
enforcer.AddGroupingPolicy("alice", "admin");      // → groupings schema
await enforcer.SavePolicyAsync();                  // Atomic commit across both

Testing

Test Coverage: 300 Tests Across 6 Frameworks

Unit Tests (186 total)

• 31 tests × 6 frameworks (net9.0, net8.0, net7.0, net6.0, net5.0, netcoreapp3.1)
• BackwardCompatibilityTest: Ensures existing single-context usage unchanged
• MultiContextTest: Validates policy routing and filtered loading

Integration Tests (114 total)

• 19 tests × 6 frameworks
• AutoSaveTests: Verifies EnableAutoSave behavior with atomic transactions
• SchemaDistributionTests: Confirms policies stored in correct schemas
• TransactionIntegrityTests: Validates atomic commit/rollback across contexts

Test Results

✅ All 300 tests passing
✅ Zero build warnings
✅ Full backward compatibility verified

Schema Extension

Extended supported schema from v0-v5 (6 columns) to v0-v13 (14 columns) to support Casbin.NET 2.16.0+ models with up to 14 policy values.

Migration Guide

Existing Users (No Changes Required)

// This continues to work unchanged
var context = new CasbinDbContext<int>(options);
var adapter = new EFCoreAdapter<int>(context);

New Multi-Context Users

1. Create contexts with shared connection
2. Implement ICasbinDbContextProvider<TKey>
3. Pass provider to new EFCoreAdapter<int>(provider)
4. Use EnableAutoSave(false) + SavePolicyAsync() for atomic operations

Documentation

• MULTI_CONTEXT_USAGE_GUIDE.md - Complete usage examples and step-by-step guide
• MULTI_CONTEXT_DESIGN.md - Technical architecture, design decisions, and limitations

Breaking Changes

None - Full backward compatibility maintained.

Dependencies

• No new dependencies added
• Casbin.NET 2.19.1 (already in use)
• EF Core versions per target framework (unchanged)

Checklist

• All tests passing (300/300 across all frameworks)
• Documentation updated (README.md, usage guide, design doc)
• Backward compatibility verified
• Integration tests for new functionality
• Example code provided

[Copilot]

Pull Request Overview

This PR adds comprehensive multi-context support to the EFCore adapter, enabling Casbin policies to be stored across separate database schemas, tables, or databases while maintaining transactional integrity where possible. The implementation introduces a provider pattern for context routing while maintaining full backward compatibility with existing single-context usage.

Key Changes:

• Introduced ICasbinDbContextProvider<TKey> interface for routing policy types to appropriate DbContext instances
• Added SingleContextProvider<TKey> for backward compatibility
• Extended adapter to coordinate transactions across multiple contexts using shared DbConnection objects
• Added comprehensive documentation and integration tests

Reviewed Changes

Copilot reviewed 33 out of 34 changed files in this pull request and generated 16 comments.

Show a summary per file

File	Description
ICasbinDbContextProvider.cs	New interface for multi-context provider pattern
SingleContextProvider.cs	Default single-context provider for backward compatibility
EFCoreAdapter.cs	Extended with multi-context constructors and transaction coordination logic
EFCoreAdapter.Internal.cs	Refactored internal methods to support context routing
DefaultPersistPolicyEntityTypeConfiguration.cs	Extended schema from v0-v5 to v0-v13 (14 columns)
README.md	Added multi-context documentation and examples
MULTI_CONTEXT_USAGE_GUIDE.md	Comprehensive step-by-step usage guide
MULTI_CONTEXT_DESIGN.md	Technical architecture and design decisions
BackwardCompatibilityTest.cs	10 tests verifying existing behavior unchanged
MultiContextTest.cs	14 tests for multi-context functionality
Integration tests	19 tests across 3 test classes verifying transaction integrity
.github/workflows/*.yml	Updated to exclude integration tests from CI/CD

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[hsluoyz]

@thoraj fix the review: #93 (review)

[thoraj]

@hsluoyz I think I handled all review comments now.

[github-actions]

🎉 This PR is included in version 2.12.0 🎉

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