Fix using docker specific ignore with read-only build context (#1349)

This PR resolves #1343.
This PR depends on apple/container-builder-shim#72.

Do not create staging directory under build context, but pass
dockerignore file bytes to the container-builder-shim.

## Type of Change
- [x] Bug fix
- [ ] New feature  
- [ ] Breaking change
- [ ] Documentation update

## Motivation and Context
[Why is this change needed?]

## Testing
- [x] Tested locally
- [ ] Added/updated tests
- [ ] Added/updated docs

Author: JaewonHur

Package.swift

@@ -22,7 +22,7 @@ import PackageDescription
 
 let releaseVersion = ProcessInfo.processInfo.environment["RELEASE_VERSION"] ?? "0.0.0"
 let gitCommit = ProcessInfo.processInfo.environment["GIT_COMMIT"] ?? "unspecified"
-let builderShimVersion = "0.11.0"
+let builderShimVersion = "0.12.0"
 let scVersion = "0.30.1"
 
 let package = Package(

Sources/ContainerBuild/Builder.swift

@@ -267,7 +267,7 @@ public struct Builder: Sendable {
         public let secrets: [String: Data]
         public let contextDir: String
         public let dockerfile: Data
-        public let hiddenDockerDir: String?
+        public let dockerignore: Data?
         public let labels: [String]
         public let noCache: Bool
         public let platforms: [Platform]
@@ -287,7 +287,7 @@ public struct Builder: Sendable {
             secrets: [String: Data],
             contextDir: String,
             dockerfile: Data,
-            hiddenDockerDir: String?,
+            dockerignore: Data?,
             labels: [String],
             noCache: Bool,
             platforms: [Platform],
@@ -306,7 +306,7 @@ public struct Builder: Sendable {
             self.secrets = secrets
             self.contextDir = contextDir
             self.dockerfile = dockerfile
-            self.hiddenDockerDir = hiddenDockerDir
+            self.dockerignore = dockerignore
             self.labels = labels
             self.noCache = noCache
             self.platforms = platforms
@@ -329,8 +329,8 @@ public struct Builder: Sendable {
         metadata.addString(config.terminal != nil ? "tty" : "plain", forKey: "progress")
         metadata.addString(config.target, forKey: "target")
 
-        if let hiddenDockerDir = config.hiddenDockerDir {
-            metadata.addString(hiddenDockerDir, forKey: "hidden-docker-dir")
+        if let dockerignore = config.dockerignore {
+            metadata.addString(dockerignore.base64EncodedString(), forKey: "dockerignore")
         }
         for tag in config.tags {
             metadata.addString(tag, forKey: "tag")

Sources/ContainerCommands/BuildCommand.swift

@@ -28,8 +28,6 @@ import TerminalProgress
 
 extension Application {
     public struct BuildCommand: AsyncLoggableCommand {
-        private static let hiddenDockerDir = ".com.apple.container.dockerfiles"
-
         public init() {}
         public static var configuration: CommandConfiguration {
             var config = CommandConfiguration()
@@ -220,7 +218,6 @@ extension Application {
 
                 let buildFileData: Data
                 var ignoreFileData: Data? = nil
-                var hiddenDockerDir: String? = nil
                 // Dockerfile should be read from stdin
                 if dockerfile == "-" {
                     let tempFile = FileManager.default.temporaryDirectory.appendingPathComponent("Dockerfile-\(UUID().uuidString)")
@@ -248,24 +245,6 @@ extension Application {
                     let ignoreFileURL = URL(filePath: dockerfile + ".dockerignore")
                     buildFileData = try Data(contentsOf: URL(filePath: dockerfile))
                     ignoreFileData = try? Data(contentsOf: ignoreFileURL)
-
-                    if var ignoreFileData {
-                        hiddenDockerDir = Self.hiddenDockerDir
-                        let hiddenDirInContext = URL(fileURLWithPath: contextDir).appendingPathComponent(Self.hiddenDockerDir)
-
-                        try FileManager.default.createDirectory(at: hiddenDirInContext, withIntermediateDirectories: true)
-                        try buildFileData.write(to: hiddenDirInContext.appendingPathComponent("Dockerfile"))
-
-                        ignoreFileData.append("\n\(Self.hiddenDockerDir)".data(using: .utf8) ?? Data())
-                        try ignoreFileData.write(to: hiddenDirInContext.appendingPathComponent("Dockerfile.dockerignore"))
-                    }
-                }
-
-                defer {
-                    if let hiddenDockerDir {
-                        let hiddenDirInContext = URL(fileURLWithPath: contextDir).appendingPathComponent(hiddenDockerDir)
-                        try? FileManager.default.removeItem(at: hiddenDirInContext)
-                    }
                 }
 
                 let secretsData: [String: Data] = try self.secrets.mapValues { secret in
@@ -351,15 +330,15 @@ extension Application {
                         return results
                     }()
                     group.addTask {
-                        [terminal, buildArg, secretsData, contextDir, hiddenDockerDir, label, noCache, target, quiet, cacheIn, cacheOut, pull, exports, imageNames, tempURL, log] in
+                        [terminal, buildArg, secretsData, contextDir, ignoreFileData, label, noCache, target, quiet, cacheIn, cacheOut, pull, exports, imageNames, tempURL, log] in
                         let config = Builder.BuildConfig(
                             buildID: buildID,
                             contentStore: RemoteContentStoreClient(),
                             buildArgs: buildArg,
                             secrets: secretsData,
                             contextDir: contextDir,
                             dockerfile: buildFileData,
-                            hiddenDockerDir: hiddenDockerDir,
+                            dockerignore: ignoreFileData,
                             labels: label,
                             noCache: noCache,
                             platforms: [Platform](platforms),

Tests/CLITests/Subcommands/Build/CLIBuilderTest.swift

@@ -1173,6 +1173,62 @@ extension TestCLIBuildBase {
             #expect(includedResult.status == 0, "included.txt should be present")
         }
 
+        // Test: Build context is read-only; Dockerfile and Dockerfile.dockerignore live outside the context
+        @Test func testDockerIgnoreReadonlyContext() throws {
+            let tempDir: URL = try createTempDir()
+            let contextDir = tempDir.appendingPathComponent("context")
+            defer {
+                // Restore write permission so the directory can be removed
+                try? FileManager.default.setAttributes(
+                    [.posixPermissions: 0o755],
+                    ofItemAtPath: contextDir.path
+                )
+                try! FileManager.default.removeItem(at: tempDir)
+            }
+
+            let dockerfile =
+                """
+                FROM ghcr.io/linuxcontainers/alpine:3.20
+                WORKDIR /app
+                COPY . .
+                """
+            // Context contains two files; Dockerfile and Dockerfile.dockerignore are placed outside
+            // the context directory (co-located in tempDir).
+            let context: [FileSystemEntry] = [
+                .file("included.txt", content: .data("This file should be included.\n".data(using: .utf8)!)),
+                .file("secret.txt", content: .data("This file should be excluded by Dockerfile.dockerignore.\n".data(using: .utf8)!)),
+            ]
+            try createContext(tempDir: tempDir, dockerfile: dockerfile, context: context)
+
+            // Write Dockerfile.dockerignore next to Dockerfile, both outside the context directory
+            let dockerignoreData = "secret.txt\n".data(using: .utf8)!
+            try dockerignoreData.write(to: tempDir.appendingPathComponent("Dockerfile.dockerignore"), options: .atomic)
+
+            // Make the context directory read-only before building
+            try FileManager.default.setAttributes(
+                [.posixPermissions: 0o555],
+                ofItemAtPath: contextDir.path
+            )
+
+            let dockerfilePath = tempDir.appendingPathComponent("Dockerfile")
+            let imageName = "registry.local/dockerignore-readonly-context:\(UUID().uuidString.prefix(6))"
+            let args = ["build", "-f", dockerfilePath.path, "-t", imageName, contextDir.path]
+            let response = try run(arguments: args)
+            if response.status != 0 {
+                throw CLIError.executionFailed("build failed: stdout=\(response.output) stderr=\(response.error)")
+            }
+
+            let containerName = "dockerignore-readonly-context-\(UUID().uuidString.prefix(6))"
+            try self.doLongRun(name: containerName, image: imageName)
+            defer { try? self.doStop(name: containerName) }
+
+            let includedResult = try run(arguments: ["exec", containerName, "test", "-f", "/app/included.txt"])
+            #expect(includedResult.status == 0, "included.txt should be present")
+
+            let secretResult = try run(arguments: ["exec", containerName, "test", "-f", "/app/secret.txt"])
+            #expect(secretResult.status != 0, "secret.txt should NOT be present (excluded by Dockerfile.dockerignore)")
+        }
+
         @Test func testNonExistingDockerfile() throws {
             let tempDir: URL = try createTempDir()
             defer {