ref(cli): Complete skill command I/O injection

Sources/CLI/cmd/agent/skills/AgentSkillsGetCommand.swift

@@ -2,7 +2,7 @@ import ArgumentParser
 
 struct AgentSkillsGetCommand: ParsableCommand, GlobalOptionsProviding {
     #if DEBUG
-        typealias Deps = any TelemetryProvider
+        typealias Deps = any (TelemetryProvider & CommandOutputWriterProvider)
     #else
         typealias Deps = Dependencies
     #endif
@@ -26,6 +26,6 @@ struct AgentSkillsGetCommand: ParsableCommand, GlobalOptionsProviding {
         guard let skill = BundledAgentSkills.skill(named: name) else {
             throw ValidationError("Unknown bundled Agent Skill '\(name)'.")
         }
-        print(skill.content)
+        deps.commandOutputWriter.write(skill.content)
     }
 }

Sources/CLI/cmd/agent/skills/AgentSkillsInstallCommand.swift

@@ -2,7 +2,7 @@ import ArgumentParser
 
 struct AgentSkillsInstallCommand: ParsableCommand, GlobalOptionsProviding {
     #if DEBUG
-        typealias Deps = any AgentSkillInstallationServiceProvider
+        typealias Deps = any (AgentSkillInstallationServiceProvider & CommandOutputWriterProvider)
     #else
         typealias Deps = Dependencies
     #endif
@@ -43,6 +43,6 @@ struct AgentSkillsInstallCommand: ParsableCommand, GlobalOptionsProviding {
             selection.selectedSkills(), root: selection.installationRoot(fileManager: deps.agentSkillFileManager()),
             dryRun: selection.dryRun, force: force
         )
-        print(output)
+        deps.commandOutputWriter.write(output)
     }
 }

Sources/CLI/cmd/agent/skills/AgentSkillsUninstallCommand.swift

@@ -2,7 +2,7 @@ import ArgumentParser
 
 struct AgentSkillsUninstallCommand: ParsableCommand, GlobalOptionsProviding {
     #if DEBUG
-        typealias Deps = any AgentSkillInstallationServiceProvider
+        typealias Deps = any (AgentSkillInstallationServiceProvider & CommandOutputWriterProvider)
     #else
         typealias Deps = Dependencies
     #endif
@@ -46,6 +46,6 @@ struct AgentSkillsUninstallCommand: ParsableCommand, GlobalOptionsProviding {
             selection.selectedSkills(), root: selection.installationRoot(fileManager: deps.agentSkillFileManager()),
             dryRun: selection.dryRun
         )
-        print(output)
+        deps.commandOutputWriter.write(output)
     }
 }

Sources/CLI/skills/AgentSkillFileSystem.swift

@@ -1,5 +1,15 @@
 import Foundation
 
+extension FileManager {
+    func readSkillData(at url: URL) throws -> Data {
+        try Data(contentsOf: url)
+    }
+
+    func writeSkillData(_ data: Data, to url: URL) throws {
+        try data.write(to: url, options: .atomic)
+    }
+}
+
 #if DEBUG
     protocol AgentSkillFileSystem {
         var currentDirectoryPath: String { get }
@@ -12,6 +22,8 @@ import Foundation
         func removeItem(at url: URL) throws
         func contentsOfDirectory(atPath path: String) throws -> [String]
         func attributesOfItem(atPath path: String) throws -> [FileAttributeKey: Any]
+        func readSkillData(at url: URL) throws -> Data
+        func writeSkillData(_ data: Data, to url: URL) throws
     }
 
     extension FileManager: AgentSkillFileSystem {}

Sources/CLI/skills/AgentSkillInstallationService.swift

@@ -119,9 +119,9 @@ struct DefaultAgentSkillInstallationService {
         if !dryRun {
             try fileManager.createDirectory(
                 at: installation.directory, withIntermediateDirectories: true, attributes: nil)
-            try content.write(to: installation.file, options: .atomic)
+            try fileManager.writeSkillData(content, to: installation.file)
             let receipt = Receipt(name: installation.skill.name, content: content)
-            try JSONEncoder().encode(receipt).write(to: installation.receiptFile, options: .atomic)
+            try fileManager.writeSkillData(JSONEncoder().encode(receipt), to: installation.receiptFile)
         }
         logger.info(dryRun ? "Would install skill" : "Installed skill", metadata: metadata)
         return "\(dryRun ? "Would install" : "Installed"): \(installation.skill.name) at \(installation.file.path)"
@@ -208,7 +208,7 @@ struct DefaultAgentSkillInstallationService {
                 metadata: ["file": .string(url.lastPathComponent)])
             throw ValidationError("Expected a regular file, not a symlink or directory, at '\(url.path)'.")
         }
-        return try Data(contentsOf: url)
+        return try fileManager.readSkillData(at: url)
     }
 
     private func fileType(_ url: URL) throws -> FileAttributeType? {

Tests/CLITests/cmd/agent/skills/AgentSkillsCommandTests.swift

@@ -19,6 +19,20 @@ struct AgentSkillsCommandTests {
         #expect(deps.telemetry.commands == ["agent.skills.list"])
     }
 
+    @Test("get writes bundled skill content through the injected output")
+    func writesSkillContent() throws {
+        // -- Arrange --
+        let command = try AgentSkillsGetCommand.parse(["apple-docs"])
+        let deps = SkillListDependencies()
+
+        // -- Act --
+        try command.run(deps: deps)
+
+        // -- Assert --
+        #expect(deps.output.lines == [BundledAgentSkills.skill(named: "apple-docs")?.content])
+        #expect(deps.telemetry.commands == ["agent.skills.get"])
+    }
+
     @Test("registers the nested list command")
     func parsesListCommand() throws {
         // -- Arrange --

Tests/CLITests/cmd/agent/skills/AgentSkillsProjectInstallationTests.swift

@@ -22,6 +22,10 @@ struct AgentSkillsProjectInstallationTests {
         #expect(
             FileManager.default.fileExists(
                 atPath: home.appendingPathComponent(".agents/skills/apple-docs/SKILL.md").path))
+        #expect(
+            deps.output.lines == [
+                "Installed: apple-docs at \(home.appendingPathComponent(".agents/skills/apple-docs/SKILL.md").path)"
+            ])
     }
 
     @Test("default uninstall uses the file manager's home directory")
@@ -43,6 +47,7 @@ struct AgentSkillsProjectInstallationTests {
         #expect(
             !FileManager.default.fileExists(
                 atPath: home.appendingPathComponent(".agents/skills/apple-docs/SKILL.md").path))
+        #expect(deps.output.lines.last == "Uninstalled: apple-docs")
     }
 
     @Test("project installation targets the Git root from a nested directory")
@@ -182,8 +187,10 @@ struct AgentSkillsProjectInstallationTests {
     }
 }
 
-private struct TestAgentSkillDependencies: AgentSkillInstallationServiceProvider {
+private struct TestAgentSkillDependencies: AgentSkillInstallationServiceProvider, CommandOutputWriterProvider {
     let fileManager: FileManager
+    let output = RecordingCommandOutputWriter()
+    var commandOutputWriter: RecordingCommandOutputWriter { output }
 
     func agentSkillFileManager() -> FileManager { fileManager }
 

Tests/CLITests/skills/AgentSkillFileSystemTests.swift

@@ -0,0 +1,87 @@
+import Foundation
+import Logging
+import Testing
+
+@testable import CLI
+
+@Suite("Agent skill file access")
+struct AgentSkillFileSystemTests {
+    @Test("installation uses injected atomic file writes")
+    func usesInjectedWriter() throws {
+        // -- Arrange --
+        let root = temporaryRoot()
+        defer { try? FileManager.default.removeItem(at: root) }
+        let skill = try #require(BundledAgentSkills.skill(named: "apple-docs"))
+        let service = DefaultAgentSkillInstallationService(
+            logger: Logger(label: "test"), fileManager: FailingDataAccessFileSystem(denied: .write))
+        let file = root.appendingPathComponent("skills/apple-docs/SKILL.md")
+
+        // -- Act --
+        #expect(throws: DataAccessDenied.self) {
+            _ = try service.install([skill], root: root.path, dryRun: false, force: false)
+        }
+
+        // -- Assert --
+        #expect(!FileManager.default.fileExists(atPath: file.path))
+    }
+
+    @Test("uninstallation uses injected file reads before deleting")
+    func usesInjectedReader() throws {
+        // -- Arrange --
+        let root = temporaryRoot()
+        defer { try? FileManager.default.removeItem(at: root) }
+        let skill = try #require(BundledAgentSkills.skill(named: "apple-docs"))
+        let installed = DefaultAgentSkillInstallationService(logger: Logger(label: "test"))
+        _ = try installed.install([skill], root: root.path, dryRun: false, force: false)
+        let service = DefaultAgentSkillInstallationService(
+            logger: Logger(label: "test"), fileManager: FailingDataAccessFileSystem(denied: .read))
+        let file = root.appendingPathComponent("skills/apple-docs/SKILL.md")
+
+        // -- Act --
+        #expect(throws: DataAccessDenied.self) {
+            _ = try service.uninstall([skill], root: root.path, dryRun: false)
+        }
+
+        // -- Assert --
+        #expect(FileManager.default.fileExists(atPath: file.path))
+    }
+
+    private func temporaryRoot() -> URL {
+        FileManager.default.temporaryDirectory.resolvingSymlinksInPath()
+            .appendingPathComponent(UUID().uuidString)
+    }
+}
+
+private enum DataAccessDenied: Error {
+    case read, write
+}
+
+private struct FailingDataAccessFileSystem: AgentSkillFileSystem {
+    let denied: DataAccessDenied
+    private let fileManager = FileManager.default
+
+    var currentDirectoryPath: String { fileManager.currentDirectoryPath }
+    var homeDirectoryForCurrentUser: URL { fileManager.homeDirectoryForCurrentUser }
+    func fileExists(atPath path: String) -> Bool { fileManager.fileExists(atPath: path) }
+    func createDirectory(
+        at url: URL, withIntermediateDirectories createIntermediates: Bool, attributes: [FileAttributeKey: Any]?
+    ) throws {
+        try fileManager.createDirectory(
+            at: url, withIntermediateDirectories: createIntermediates, attributes: attributes)
+    }
+    func removeItem(at url: URL) throws { try fileManager.removeItem(at: url) }
+    func contentsOfDirectory(atPath path: String) throws -> [String] {
+        try fileManager.contentsOfDirectory(atPath: path)
+    }
+    func attributesOfItem(atPath path: String) throws -> [FileAttributeKey: Any] {
+        try fileManager.attributesOfItem(atPath: path)
+    }
+    func readSkillData(at url: URL) throws -> Data {
+        if denied == .read { throw DataAccessDenied.read }
+        return try Data(contentsOf: url)
+    }
+    func writeSkillData(_ data: Data, to url: URL) throws {
+        if denied == .write { throw DataAccessDenied.write }
+        try data.write(to: url, options: .atomic)
+    }
+}

Tests/CLITests/telemetry/TelemetryTests.swift

@@ -76,8 +76,9 @@ struct TelemetryTests {
     }
 }
 
-private struct CommandDeps: TelemetryProvider {
+private struct CommandDeps: TelemetryProvider, CommandOutputWriterProvider {
     let telemetry: CommandTelemetryRecorder
+    let commandOutputWriter = RecordingCommandOutputWriter()
 }
 
 private final class CommandTelemetryRecorder: Telemetry, @unchecked Sendable {