Write tools config in genkit init. (#117)

Author: apascal07

genkit-tools/cli/config/nextjs.genkit-tools.config.js.template

@@ -0,0 +1,6 @@
+module.exports = {
+  runner: {
+    mode: 'harness',
+    files: [$GENKIT_HARNESS_FILES],
+  },
+};

genkit-tools/cli/src/commands/init.ts

@@ -150,6 +150,9 @@ const sampleTemplatePaths: Record<Platform, string> = {
   nextjs: '../../config/nextjs.genkit.ts.template',
 };
 
+const nextjsToolsConfigTemplatePath =
+  '../../config/nextjs.genkit-tools.config.js.template';
+
 /** Supported runtimes for the init command. */
 const supportedRuntimes: Runtime[] = ['node'];
 
@@ -250,6 +253,7 @@ export const init = new Command('init')
       ) {
         generateSampleFile(platform, modelOptions[model].plugin, plugins);
       }
+      generateToolsConfig(platform);
     } catch (error) {
       logger.error(error);
       process.exit(1);
@@ -325,6 +329,28 @@ async function updatePackageJson() {
   fs.writeFileSync(packageJsonPath, JSON.stringify(newPackageJson, null, 2));
 }
 
+/**
+ * Generates an appropriate tools config for the given platform.
+ * @param platform platform
+ */
+function generateToolsConfig(platform: Platform) {
+  if (platform === 'nextjs') {
+    const templatePath = path.join(__dirname, nextjsToolsConfigTemplatePath);
+    let template = fs.readFileSync(templatePath, 'utf8');
+    if (fs.existsSync('src/app')) {
+      template = template.replace('$GENKIT_HARNESS_FILES', `'./src/app/*.ts'`);
+    } else if (fs.existsSync('app')) {
+      template = template.replace('$GENKIT_HARNESS_FILES', `'./app/*.js'`);
+    } else {
+      throw new Error(
+        'Unable to resolve source folder (app or src/app) of you next.js app.'
+      );
+    }
+    const configPath = path.join(process.cwd(), 'genkit-tools.conf.js');
+    fs.writeFileSync(configPath, template, 'utf8');
+  }
+}
+
 /**
  * Generates a sample index.ts file.
  * @param platform Deployment platform.

genkit-tools/common/src/runner/runner.ts

@@ -110,11 +110,13 @@ export class Runner {
     }
     if (this.autoReload) {
       const config = await findToolsConfig();
-      this.buildCommand = config?.builder?.cmd;
-      if (!this.buildCommand && detectRuntime(process.cwd()) === 'node') {
-        this.buildCommand = 'npm run build';
+      if (config?.runner?.mode !== 'harness') {
+        this.buildCommand = config?.builder?.cmd;
+        if (!this.buildCommand && detectRuntime(process.cwd()) === 'node') {
+          this.buildCommand = 'npm run build';
+        }
+        this.build();
       }
-      this.build();
       this.watchForChanges();
     }
     return this.startApp();