Refactor repository lookup

Add dwim subscript accessor to repository

Author: mattt

Sources/Git/Object.swift

@@ -25,8 +25,7 @@ public class Object {
 
     required init(_ pointer: OpaquePointer) {
         self.pointer = pointer
-        assert(Swift.type(of: self) == Object.self ||
-                git_object_type(pointer) == Swift.type(of: self).type)
+        assert(Swift.type(of: self) == Object.self || git_object_type(pointer) == Swift.type(of: self).type)
     }
 
     deinit {
@@ -35,6 +34,15 @@ public class Object {
         }
     }
 
+    class func type(of object: Object) -> Object.Type? {
+        return Object.type(of: object.pointer)
+    }
+
+    class func type(of pointer: OpaquePointer?) -> Object.Type? {
+        guard let pointer = pointer else { return nil }
+        return Object.type(of: git_object_type(pointer))
+    }
+
     class func type(of value: git_object_t?) -> Object.Type? {
         switch value {
         case GIT_OBJECT_ANY?:

Sources/Git/Objects/Commit.swift

@@ -12,15 +12,15 @@ public final class Commit: Object {
     /// The tree containing the commit, if any.
     public var tree: Tree? {
         let id = Object.ID(rawValue: git_commit_tree_id(pointer).pointee)
-        return try? owner.lookup(id)
+        return try? owner.lookup(type: Tree.self, with: id)
     }
 
     /// The parents of the commit.
     public var parents: [Commit] {
         var parents: [Commit] = []
         for n in 0..<git_commit_parentcount(pointer) {
             let id = Object.ID(rawValue: git_commit_parent_id(pointer, n).pointee)
-            guard let commit = try? owner.lookup(id) as? Commit else { continue }
+            guard let commit = try? owner.lookup(type: Commit.self, with: id) else { continue }
             parents.append(commit)
         }
 

Sources/Git/Reference.swift

@@ -86,6 +86,21 @@ public class Reference/*: Identifiable */ {
     public var owner: Repository {
         return Repository(git_reference_owner(pointer))
     }
+
+    var target: Object? {
+        let id: Object.ID
+        switch git_reference_type(pointer) {
+        case GIT_REFERENCE_SYMBOLIC:
+            var resolved: OpaquePointer?
+            guard case .success = result(of: { git_reference_resolve(&resolved, pointer) }) else { return nil }
+            defer { git_reference_free(resolved) }
+            id = Object.ID(rawValue: git_reference_target(resolved).pointee)
+        default:
+            id = Object.ID(rawValue: git_reference_target(pointer).pointee)
+        }
+
+        return try? owner.lookup(type: Object.self, with: id)
+    }
 }
 
 // MARK: - Equatable

Sources/Git/References/Branch.swift

@@ -15,7 +15,7 @@ public final class Branch: Reference {
             id = Object.ID(rawValue: git_reference_target(pointer).pointee)
         }
 
-        return try? owner.lookup(id)
+        return try? owner.lookup(type: Commit.self, with: id)
     }
 
     /// The short name of the branch.

Sources/Git/References/Note.swift

@@ -15,8 +15,8 @@ public final class Note: Reference {
     }
 
     /// The target of the reference.
-    public var target: Object? {
-        try? owner.lookup(Object.ID { oid in
+    public override var target: Object? {
+        try? owner.lookup(type: Object.self, with: Object.ID { oid in
             git_note_id(pointer)
         })
     }

Sources/Git/References/Tag.swift

@@ -8,17 +8,11 @@ public final class Tag: Reference {
     }
 
     /// The target of the reference.
-    public var target: Object? {
+    public override var target: Object? {
         var target: OpaquePointer?
         guard case .success = result(of: { git_tag_target(&target, self.pointer) }) else { return nil }
         return Object.type(of: git_tag_target_type(self.pointer))?.init(target!)
     }
-
-    public func peel() throws -> Object? {
-        var pointer: OpaquePointer?
-        try attempt { git_tag_peel(&pointer, self.pointer) }
-        return Object(pointer!)
-    }
 }
 
 // MARK: -
@@ -44,6 +38,12 @@ extension Tag {
         public var message: String? {
             return String(validatingUTF8: git_tag_message(pointer))
         }
+
+        public func peel<T: Object>() throws -> T? {
+            var pointer: OpaquePointer?
+            try attempt { git_tag_peel(&pointer, self.pointer) }
+            return T(pointer!)
+        }
     }
 
 //    /// The tag's annotation, if any.

Sources/Git/Repository.swift

@@ -45,7 +45,7 @@ public final class Repository {
     public static func clone(from remoteURL: URL,
                              to localURL: URL,
                              configuration: Clone.Configuration = .default) throws -> Repository {
-        var pointer: OpaquePointer? = nil
+        var pointer: OpaquePointer?
 
         var options = configuration.rawValue
         let remoteURLString = remoteURL.isFileURL ? remoteURL.path : remoteURL.absoluteString
@@ -58,6 +58,15 @@ public final class Repository {
 
     // MARK: -
 
+    public subscript<T: Reference>(_ shorthand: String) -> T? {
+        var pointer: OpaquePointer?
+        guard case .success = result(of: { git_reference_dwim(&pointer, self.pointer, shorthand) }),
+              pointer != nil
+        else { return nil }
+
+        return T(pointer!)
+    }
+
     /**
      The repository's working directory.
 
@@ -83,7 +92,8 @@ public final class Repository {
     public lazy var index: Index? = {
         var pointer: OpaquePointer?
         guard case .success = result(of: { git_repository_index(&pointer, self.pointer) }),
-              pointer != nil else { return nil }
+              pointer != nil
+        else { return nil }
         let index = Index(pointer!)
         index.managed = true
 
@@ -124,14 +134,26 @@ public final class Repository {
      - Throws: An error if no object exists for the
      - Returns: The corresponding object.
      */
-    public func lookup<T: Object>(_ id: Object.ID) throws -> T? {
-        var result: OpaquePointer? = nil
+    func lookup<T: Object>(type: T.Type, with id: Object.ID) throws -> T? {
+        var pointer: OpaquePointer?
         var oid = id.rawValue
-        try attempt { git_object_lookup(&result, self.pointer, &oid, T.type) }
+        try attempt { git_object_lookup(&pointer, self.pointer, &oid, T.type) }
 //        defer { git_object_free(pointer) }
-        guard let pointer = result else { return nil }
 
-        return T(pointer)
+        switch type {
+        case is Blob.Type,
+             is Commit.Type,
+             is Tree.Type:
+            return T(pointer!)
+        default:
+            return Object.type(of: pointer)?.init(pointer!) as? T
+        }
+    }
+
+    func lookup<T: Reference>(type: T.Type, named name: String) throws -> T? {
+        var pointer: OpaquePointer?
+        try attempt { git_reference_lookup(&pointer, self.pointer, name) }
+        return T(pointer!)
     }
 
     /**
@@ -170,16 +192,16 @@ public final class Repository {
 
     @discardableResult
     public func createCommit(message: String, author: Signature? = nil, committer: Signature? = nil) throws -> Commit {
-        let tree = try lookup(try Object.ID { oid in
+        let tree = try lookup(type: Tree.self, with: try Object.ID { oid in
             try attempt { git_index_write_tree(oid, index?.pointer) }
-        }) as Tree?
+        })
 
         var committer = (try committer ?? author ?? Signature.default(for: self)).rawValue
         var author = (try author ?? Signature.default(for: self)).rawValue
 
         var parents = [head?.commit].compactMap { $0?.pointer } as [OpaquePointer?]
 
-        return try lookup(try Object.ID { oid in
+        return try lookup(type: Commit.self, with: try Object.ID { oid in
             try attempt { git_commit_create(oid, pointer, "HEAD", &author, &committer, "UTF-8", message, tree?.pointer, parents.count, &parents) }
         })!
     }

Sources/Git/Repository/Index.swift

@@ -174,7 +174,7 @@ extension Repository.Index {
         /// The blob object for the index entry, if any.
         public var blob: Blob? {
             let id = Object.ID(rawValue: rawValue.id)
-            return try? index?.owner.lookup(id)
+            return try? index?.owner.lookup(type: Blob.self, with: id)
         }
 
         public var isConflict: Bool {

Sources/Git/RevisionWalker.swift

@@ -94,7 +94,7 @@ extension Repository {
             defer { pointer.deallocate() }
             guard case .success = result(of: { git_revwalk_next(pointer, self.pointer) }) else { return nil }
             let id = Object.ID(rawValue: pointer.pointee)
-            return try? repository.lookup(id)
+            return try? repository.lookup(type: Commit.self, with: id)
         }
 
         // MARK: - RevisionWalker

Tests/GitTests/GitTests.swift

@@ -104,6 +104,10 @@ final class GitTests: XCTestCase {
         try repository.createLightweightTag(named: "0.0.1", target: commit)
         let names = try repository.tagNames()
         XCTAssert(names.contains("0.0.1"))
+
+        XCTAssertEqual((repository["0.0.1"]?.target as? Commit)?.message, "Initial commit")
+        XCTAssertEqual((repository["master"]?.target as? Commit)?.message, "Initial commit")
+        XCTAssertEqual((repository["HEAD"]?.target as? Commit)?.message, "Initial commit")
     }
 }