fix(service): support Compose 2.x dict form for env_file entries

Sources/Container-Compose/Codable Structs/Service.swift

@@ -200,11 +200,31 @@ public struct Service: Codable, Hashable {
             environment = nil
         }
 
-        // Decode 'env_file' which can be either a single string or an array of strings.
-        if let envFileArray = try? container.decodeIfPresent([String].self, forKey: .env_file) {
-            env_file = envFileArray
-        } else if let envFileString = try? container.decodeIfPresent(String.self, forKey: .env_file) {
-            env_file = [envFileString]
+        // `env_file` accepts three forms per the Compose spec:
+        //   env_file: path.env               → single string
+        //   env_file: [path1.env, path2.env] → array of strings
+        //   env_file:                         → array of {path:, required:?} dicts (Compose 2.x extended form)
+        //     - path: optional.env
+        //       required: false
+        // Arrays may also mix plain strings and dict entries.
+        // Missing optional files (required: false) are loaded silently as empty — loadEnvFile
+        // already suppresses read errors, which is the correct behaviour for optional files.
+        struct EnvFileEntry: Decodable {
+            let path: String
+            init(from decoder: Decoder) throws {
+                if let s = try? decoder.singleValueContainer().decode(String.self) {
+                    path = s
+                } else {
+                    enum Keys: String, CodingKey { case path }
+                    let c = try decoder.container(keyedBy: Keys.self)
+                    path = try c.decode(String.self, forKey: .path)
+                }
+            }
+        }
+        if let entries = try? container.decodeIfPresent([EnvFileEntry].self, forKey: .env_file) {
+            env_file = entries.map(\.path)
+        } else if let single = try? container.decodeIfPresent(String.self, forKey: .env_file) {
+            env_file = [single]
         } else {
             env_file = nil
         }

Tests/Container-Compose-StaticTests/EnvFileDictFormTests.swift

@@ -0,0 +1,129 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2025 Morris Richman and the Container-Compose project authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Testing
+import Foundation
+@testable import Yams
+@testable import ContainerComposeCore
+
+/// Tests for the Compose 2.x extended `env_file` dict form:
+///   env_file:
+///     - path: ./config.env
+///       required: false
+///
+/// The dict form may appear alone, alongside plain string entries in the same
+/// array, or as the sole `env_file` value. All three must decode correctly.
+@Suite("env_file dict-form parsing")
+struct EnvFileDictFormTests {
+
+    private func decodeService(_ serviceYaml: String) throws -> Service {
+        let yaml = """
+        services:
+          svc:
+        \(serviceYaml.split(separator: "\n", omittingEmptySubsequences: false)
+            .map { "    \($0)" }.joined(separator: "\n"))
+        """
+        let compose = try YAMLDecoder().decode(DockerCompose.self, from: yaml)
+        guard let service = compose.services["svc"].flatMap({ $0 }) else {
+            Issue.record("service 'svc' missing or nil")
+            throw TestError.missingService
+        }
+        return service
+    }
+
+    enum TestError: Error { case missingService }
+
+    // MARK: - Regression: existing string forms still parse
+
+    @Test("plain string env_file still parses")
+    func plainString() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file: config/app.env
+        """)
+        #expect(svc.env_file == ["config/app.env"])
+    }
+
+    @Test("array of plain strings env_file still parses")
+    func arrayOfStrings() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file:
+            - config/app.env
+            - config/secrets.env
+        """)
+        #expect(svc.env_file == ["config/app.env", "config/secrets.env"])
+    }
+
+    // MARK: - New: dict form
+
+    @Test("single dict entry extracts path")
+    func singleDictEntry() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file:
+            - path: config/generated.env
+              required: false
+        """)
+        #expect(svc.env_file == ["config/generated.env"])
+    }
+
+    @Test("dict entry with required: true extracts path")
+    func dictEntryRequired() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file:
+            - path: config/app.env
+              required: true
+        """)
+        #expect(svc.env_file == ["config/app.env"])
+    }
+
+    @Test("dict entry without required field extracts path")
+    func dictEntryNoRequired() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file:
+            - path: config/app.env
+        """)
+        #expect(svc.env_file == ["config/app.env"])
+    }
+
+    @Test("multiple dict entries extract all paths in order")
+    func multipleDictEntries() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file:
+            - path: config/base.env
+              required: true
+            - path: config/optional.env
+              required: false
+        """)
+        #expect(svc.env_file == ["config/base.env", "config/optional.env"])
+    }
+
+    @Test("mixed array of strings and dict entries extracts all paths")
+    func mixedArray() throws {
+        let svc = try decodeService("""
+          image: alpine
+          env_file:
+            - config/base.env
+            - path: config/generated.env
+              required: false
+        """)
+        #expect(svc.env_file == ["config/base.env", "config/generated.env"])
+    }
+}