Add support for conditionally compiled protocol members

[bfahey]

📝 Summary

Protocols with #if/#elseif/#else/#endif blocks now have their members correctly mocked with the conditional compilation structure preserved. This includes support for methods, properties, initializers, and associated types within conditional blocks.

What changed

• Conditional members are preserved structurally
  • The macro now preserves the full #if/#elseif/#else structure when generating mocked initializers, properties, and methods.
• Associated types under #if are handled safely
  • Associated types declared inside conditional compilation blocks are extracted as generic parameters on the mock.
  • When associated types have branch-specific constraints (inheritance or where clauses), the mock no longer hardcodes a single constraint.
  • Instead, the mock conditionally conforms to the protocol via per-clause extension declarations with the correct where constraints for each branch.
• Associated-type generic where clauses are respected
  • Constraints like where Base.Element: Equatable are now correctly carried into conditional conformance extensions.
• Conditional conformance is only used when necessary
  • If conditional associated types are unconstrained across branches, the mock simply adds the generic parameter and conforms to the protocol unconditionally.

Known limitations / follow-ups

These cases are intentionally not handled yet and will require a more holistic approach in a future PR:

• Multiple independent top-level #if blocks with constrained associated types
  • Correct handling requires combining constraints across all active branches to avoid duplicate protocol conformances.
• Nested #if blocks containing associated types
  • Supporting this correctly requires recursive traversal and per-configuration constraint aggregation.
• Cross-branch semantic equivalence of constraints
  • The macro does not attempt to detect when constraints are semantically identical but syntactically different (e.g. Equatable & Hashable vs Hashable & Equatable).

These deferred cases all require branch-combination logic and are planned to be addressed together in a follow-up. An issue (#139) has been created to track these edge cases.

🛠️ Type of Change

• Bug fix (change that fixes an issue)
• New feature (change that adds functionality)
• Breaking change (bug fix or feature that is not backwards compatible)
• Documentation (DocC, API docs, markdown files, templates, etc.)
• Testing (new tests, updated tests, etc.)
• Refactoring or code formatting (no logic changes)
• Updating dependencies (Swift packages, Homebrew, etc.)
• CI/CD (change to automated workflows)
• Chore (other maintenance)

🧪 How Has This Been Tested?

• New unit tests have been added.
• All existing unit tests still pass.

🔗 Related PRs or Issues

Closes #136

✅ Checklist

• I have added relevant tests
• I have verified all tests pass
• I have formatted my code using SwiftFormat
• I have updated documentation (if needed)
• I have added the appropriate label to my PR
• I have read the contributing guidelines
• I agree to follow this project's Code of Conduct

[codecov]

Codecov Report

❌ Patch coverage is 99.23664% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.34%. Comparing base (ef30af4) to head (5e1561b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...MockingMacros/Macros/MockedMacro/MockedMacro.swift	99.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #137      +/-   ##
==========================================
+ Coverage   69.76%   73.34%   +3.58%     
==========================================
  Files          73       73              
  Lines        3678     3846     +168     
==========================================
+ Hits         2566     2821     +255     
+ Misses       1112     1025      -87     

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[graycampbell]

Some comments/suggestions from my first pass through this

[berbs-fetch]

Suggested change

	var seenNames: Set<String> = []
	let uniqueAssociatedTypes = associatedTypeDeclarations.filter { decl in
	var seenNames = Set<String>()
	let uniqueAssociatedTypes = associatedTypeDeclarations.filter {
	seenNames.insert($0.name.text).inserted
	}

Q: Does order matter? If not then Set(associatedTypeDeclarations) will work

[graycampbell]

There's a hole in how all of this is implemented at the moment. See my comment below about the mock's generic parameter constraints.

[graycampbell]

There are still some issues with this implementation:

1) Nested #if blocks are not detected

conflictingConditionalClauses only checks for AssociatedTypeDeclSyntax that are direct children of each IfConfigDeclSyntax clause.

If a clause contains another #if (i.e. a nested IfConfigDeclSyntax), this finds zero associated types and returns nil, so conditional conformance is not triggered.

Example:

protocol SomeCollection {
    #if DEBUG
        #if os(iOS)
        associatedtype Item: Hashable
        #else
        associatedtype Item: Equatable
        #endif
    #else
        #if os(iOS)
        associatedtype Item: Sendable
        #else
        associatedtype Item: Codable
        #endif
    #endif
}

Here, the outer #if clauses only contain another #if, so no associated types are detected at that level.

2) Associated type generic where clauses are missed

whereClause(from:) only extracts constraints from the associated type’s inheritance clause and ignores the associated type’s own genericWhereClause.

For example:

protocol SomeCollection {
    #if os(iOS)
    associatedtype Base: RandomAccessCollection & Equatable where Base.Element: Equatable
    #elseif os(macOS)
    associatedtype Base: RandomAccessCollection & Hashable where Base.Element: Hashable
    #else
    associatedtype Base: RandomAccessCollection & Codable where Base.Element: Codable
    #endif
}

In this scenario, the generated extensions that provide conditional conformance won't include the generic where clauses from the associate type declarations, so conditional conformance will be incomplete.