Support reset value in Docker Compose

Fixes #7919

core/src/main/java/org/testcontainers/containers/ParsedDockerComposeFile.java

@@ -11,6 +11,8 @@
 import org.yaml.snakeyaml.LoaderOptions;
 import org.yaml.snakeyaml.Yaml;
 import org.yaml.snakeyaml.constructor.SafeConstructor;
+import org.yaml.snakeyaml.nodes.Node;
+import org.yaml.snakeyaml.nodes.Tag;
 import org.yaml.snakeyaml.representer.Representer;
 import org.yaml.snakeyaml.resolver.Resolver;
 
@@ -44,13 +46,17 @@ class ParsedDockerComposeFile {
         LoaderOptions options = new LoaderOptions();
         options.setMaxAliasesForCollections(1_000);
         DumperOptions dumperOptions = new DumperOptions();
-        Yaml yaml = new Yaml(
-            new SafeConstructor(options),
-            new Representer(dumperOptions),
-            dumperOptions,
-            options,
-            new Resolver()
-        );
+
+        SafeConstructor constructor = new SafeConstructor(options) {
+            @Override
+            protected Object constructObject(Node node) {
+                if (node.getTag().equals(new Tag("!reset"))) {
+                    return null;
+                }
+                return super.constructObject(node);
+            }
+        };
+        Yaml yaml = new Yaml(constructor, new Representer(dumperOptions), dumperOptions, options, new Resolver());
         try (FileInputStream fileInputStream = FileUtils.openInputStream(composeFile)) {
             composeFileContent = yaml.load(fileInputStream);
         } catch (Exception e) {

core/src/test/java/org/testcontainers/junit/ComposeContainerOverrideTest.java

@@ -0,0 +1,41 @@
+package org.testcontainers.junit;
+
+import com.github.dockerjava.api.DockerClient;
+import com.github.dockerjava.api.command.InspectContainerResponse;
+import org.junit.Test;
+import org.testcontainers.DockerClientFactory;
+import org.testcontainers.containers.ComposeContainer;
+import org.testcontainers.containers.ContainerState;
+
+import java.io.File;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ComposeContainerOverrideTest {
+
+    private static final File BASE = new File("src/test/resources/compose-override/compose.yml");
+
+    private static final File OVERRIDE = new File("src/test/resources/compose-override/compose-override.yml");
+
+    @Test
+    public void readEnvironment() {
+        try (ComposeContainer compose = new ComposeContainer(BASE).withExposedService("redis", 6379)) {
+            compose.start();
+            DockerClient dockerClient = DockerClientFactory.lazyClient();
+            String containerId = compose.getContainerByServiceName("redis-1").map(ContainerState::getContainerId).get();
+            InspectContainerResponse container = dockerClient.inspectContainerCmd(containerId).exec();
+            assertThat(container.getConfig().getEnv()).contains("foo=bar");
+        }
+    }
+
+    @Test
+    public void resetEnvironment() {
+        try (ComposeContainer compose = new ComposeContainer(BASE, OVERRIDE).withExposedService("redis", 6379)) {
+            compose.start();
+            DockerClient dockerClient = DockerClientFactory.lazyClient();
+            String containerId = compose.getContainerByServiceName("redis-1").map(ContainerState::getContainerId).get();
+            InspectContainerResponse container = dockerClient.inspectContainerCmd(containerId).exec();
+            assertThat(container.getConfig().getEnv()).doesNotContain("foo=bar");
+        }
+    }
+}

core/src/test/resources/compose-override/compose-override.yml

@@ -0,0 +1,7 @@
+services:
+  redis:
+    image: redis:6-alpine
+    ports:
+      - 6379
+    environment:
+      foo: !reset null

core/src/test/resources/compose-override/compose.yml

@@ -0,0 +1,7 @@
+services:
+  redis:
+    image: redis:6-alpine
+    ports:
+      - 6379
+    environment:
+      foo: bar