feat: Add optional Docker extraHosts (part 2)

package.json

@@ -35,7 +35,7 @@
     "@junobuild/admin": "^4.2.1",
     "@junobuild/cdn": "^2.3.1",
     "@junobuild/cli-tools": "^0.12.3",
-    "@junobuild/config": "^2.14.2",
+    "@junobuild/config": "^2.14.2", // TODO: Bump this to the version with extraHosts support.
     "@junobuild/config-loader": "^0.4.9",
     "@junobuild/core": "^5.2.2",
     "@junobuild/functions-tools": "^0.5.3",

src/configs/emulator.config.ts

@@ -40,6 +40,8 @@ export const readEmulatorConfig = async (): Promise<
 
   const targetDeploy = config.runner?.target ?? DEPLOY_LOCAL_REPLICA_PATH;
 
+  const extraHosts = (config.runner?.extraHosts ?? []).map(([hostname, destination]) => `${hostname}:${destination}`);
+
   return {
     success: true,
     config: {
@@ -48,7 +50,8 @@ export const readEmulatorConfig = async (): Promise<
         containerName,
         emulatorType,
         runner,
-        targetDeploy
+        targetDeploy,
+        extraHosts
       }
     }
   };

src/services/emulator/_runner.services.ts

@@ -151,7 +151,7 @@ const initConfigFile = async () => {
 const startEmulator = async ({config: extendedConfig}: {config: CliEmulatorConfig}) => {
   const {
     config,
-    derivedConfig: {emulatorType, containerName, runner, targetDeploy}
+    derivedConfig: {emulatorType, containerName, runner, targetDeploy, extraHosts}
   } = extendedConfig;
 
   const {running} = await assertContainerRunning({containerName, runner});
@@ -249,6 +249,10 @@ const startEmulator = async ({config: extendedConfig}: {config: CliEmulatorConfi
       '-v',
       `${targetDeploy}:/juno/target/deploy`,
       ...(nonNullish(platform) ? [`--platform=${platform}`] : []),
+      // Inject extra host-to-IP mappings so services on the host machine
+      // (e.g. a local Ethereum RPC node) are reachable inside the container
+      // via a stable hostname like host.docker.internal.
+      ...extraHosts.flatMap((host) => ['--add-host', host]),
       image
     ]
   });

src/types/emulator.ts

@@ -11,6 +11,24 @@ export interface CliEmulatorDerivedConfig {
   runner: EmulatorRunnerType;
   emulatorType: EmulatorType;
   targetDeploy: string;
+  /**
+   * Additional host-to-IP mappings injected into the container via `--add-host`.
+   * Format: `"hostname:ip"` or `"hostname:host-gateway"`.
+   *
+   * This is useful for making host-machine services (e.g. a local Ethereum RPC node)
+   * reachable from within the container under a stable DNS name such as
+   * `host.docker.internal`.
+   *
+   * @example
+   * ```ts
+   * runner: {
+   *   extraHosts: ['host.docker.internal:host-gateway']
+   * }
+   * ```
+   *
+   * @see https://docs.docker.com/reference/cli/docker/container/run/#add-host
+   */
+  extraHosts: string[];
 }
 
 export interface CliEmulatorConfig {