fix: codebase preview in standalone mode

- Fix standalone bundle path lookup in worker to not add redundant file
  extension (the path already contains .tar/.esm suffixes from the API)
- Fix CLI preview tar bundle handling to preserve binary data correctly
  (was using btoa(blob.text()) which corrupted binary tar data)
- Add integration tests for script/flow preview commands covering:
  - Regular scripts (non-codebase)
  - Codebase scripts (CJS and ESM formats)
  - Codebase scripts with assets (tar bundles)
  - Flow preview

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/windmill-worker/src/bun_executor.rs

@@ -635,10 +635,9 @@ async fn pull_codebase(w_id: &str, id: &str, job_dir: &str) -> Result<PulledCode
             && object_store.is_none()
         {
             let bun_cache_path = format!(
-                "{}/{}.{}",
+                "{}/{}",
                 *windmill_common::worker::ROOT_STANDALONE_BUNDLE_DIR,
-                path,
-                if is_tar { "tar" } else { "js" }
+                path
             );
             if std::fs::metadata(&bun_cache_path).is_ok() {
                 tracing::info!("loading {bun_cache_path} from standalone bundle cache");

cli/src/commands/script/script.ts

@@ -1125,7 +1125,7 @@ async function preview(
   const codebase =
     language == "bun" ? findCodebase(filePath, codebases) : undefined;
 
-  let bundledContent: string | undefined = undefined;
+  let bundledContent: string | Blob | undefined = undefined;
   let isTar = false;
 
   if (codebase) {
@@ -1179,8 +1179,7 @@ async function preview(
           const fil = new File([file.contents as any], file.path.substring(1));
           tarball.append(fil);
         }
-        const blob = await streamToBlob(tarball.stream());
-        bundledContent = btoa(await blob.text());
+        bundledContent = await streamToBlob(tarball.stream());
         isTar = true;
       } else if (Array.isArray(codebase.assets) && codebase.assets.length > 0) {
         // Handle assets
@@ -1196,14 +1195,14 @@ async function preview(
           const file = new File([blob], asset.to);
           tarball.append(file);
         }
-        const blob = await streamToBlob(tarball.stream());
-        bundledContent = btoa(await blob.text());
+        bundledContent = await streamToBlob(tarball.stream());
         isTar = true;
       }
 
       if (!opts.silent) {
+        const size = typeof bundledContent === "string" ? bundledContent.length : bundledContent.size;
         log.info(
-          `Bundled ${filePath}: ${(bundledContent.length / 1024).toFixed(0)}kB (${(
+          `Bundled ${filePath}: ${(size / 1024).toFixed(0)}kB (${(
             endTime - startTime
           ).toFixed(0)}ms)`
         );
@@ -1229,7 +1228,9 @@ async function preview(
     form.append("preview", JSON.stringify(previewPayload));
     form.append(
       "file",
-      new Blob([bundledContent], { type: "application/javascript" })
+      typeof bundledContent === "string"
+        ? new Blob([bundledContent], { type: "application/javascript" })
+        : bundledContent
     );
 
     const url =

cli/test/preview.test.ts

@@ -0,0 +1,347 @@
+import { assertEquals, assertStringIncludes } from "https://deno.land/std@0.224.0/assert/mod.ts";
+import { withTestBackend, cleanupTestBackend } from "./test_backend.ts";
+
+// =============================================================================
+// PREVIEW COMMAND INTEGRATION TESTS
+// Tests for `wmill script preview` and `wmill flow preview` commands
+//
+// These tests require a backend to run. Run with:
+//   deno test --allow-all test/preview.test.ts
+//
+// The tests cover:
+// - Regular script preview (non-codebase)
+// - Codebase script preview (CJS format)
+// - Codebase script preview (ESM format)
+// - Codebase script preview with assets (tar bundle)
+// - Codebase script preview with ESM + tar
+// - Flow preview
+// =============================================================================
+
+// Helper to create a wmill.yaml config file
+async function createWmillConfig(
+  tempDir: string,
+  config: {
+    defaultTs?: "bun" | "deno";
+    codebases?: Array<{
+      relative_path: string;
+      includes?: string[];
+      format?: "cjs" | "esm";
+      assets?: Array<{ from: string; to: string }>;
+    }>;
+  }
+): Promise<void> {
+  let yamlContent = `defaultTs: ${config.defaultTs ?? "bun"}\n`;
+
+  if (config.codebases && config.codebases.length > 0) {
+    yamlContent += "codebases:\n";
+    for (const cb of config.codebases) {
+      yamlContent += `  - relative_path: ${cb.relative_path}\n`;
+      yamlContent += "    includes:\n";
+      for (const inc of cb.includes ?? ["**"]) {
+        yamlContent += `      - "${inc}"\n`;
+      }
+      if (cb.format) {
+        yamlContent += `    format: ${cb.format}\n`;
+      }
+      if (cb.assets && cb.assets.length > 0) {
+        yamlContent += "    assets:\n";
+        for (const asset of cb.assets) {
+          yamlContent += `      - from: ${asset.from}\n`;
+          yamlContent += `        to: ${asset.to}\n`;
+        }
+      }
+    }
+  }
+
+  await Deno.writeTextFile(`${tempDir}/wmill.yaml`, yamlContent);
+}
+
+// Helper to create a script file with metadata
+async function createScript(
+  tempDir: string,
+  path: string,
+  content: string,
+  metadata?: {
+    summary?: string;
+    description?: string;
+  }
+): Promise<void> {
+  const dir = `${tempDir}/${path.substring(0, path.lastIndexOf("/"))}`;
+  await Deno.mkdir(dir, { recursive: true });
+  await Deno.writeTextFile(`${tempDir}/${path}`, content);
+
+  // Create metadata file
+  const metaPath = path.replace(/\.[^.]+$/, ".script.yaml");
+  const metaContent = `summary: "${metadata?.summary ?? "Test script"}"
+description: "${metadata?.description ?? "Test script description"}"
+lock: ""
+schema:
+  $schema: "https://json-schema.org/draft/2020-12/schema"
+  type: object
+  properties:
+    name:
+      type: string
+      default: "World"
+  required: []
+`;
+  await Deno.writeTextFile(`${tempDir}/${metaPath}`, metaContent);
+}
+
+// Helper to create a flow directory with flow.yaml
+async function createFlow(
+  tempDir: string,
+  flowPath: string,
+  options: {
+    summary: string;
+    scriptContent: string;
+  }
+): Promise<void> {
+  const dir = `${tempDir}/${flowPath}`;
+  await Deno.mkdir(dir, { recursive: true });
+
+  const flowYaml = `summary: "${options.summary}"
+description: "Test flow"
+value:
+  modules:
+    - id: "a"
+      value:
+        type: "rawscript"
+        language: "bun"
+        content: |
+${options.scriptContent.split("\n").map(line => `          ${line}`).join("\n")}
+schema:
+  $schema: "https://json-schema.org/draft/2020-12/schema"
+  type: object
+  properties:
+    name:
+      type: string
+      default: "World"
+  required: []
+`;
+  await Deno.writeTextFile(`${dir}/flow.yaml`, flowYaml);
+}
+
+// =============================================================================
+// SCRIPT PREVIEW TESTS
+// =============================================================================
+
+Deno.test({
+  name: "script preview: regular script (non-codebase)",
+  async fn() {
+    await withTestBackend(async (backend, tempDir) => {
+      await createWmillConfig(tempDir, { defaultTs: "bun" });
+      await createScript(
+        tempDir,
+        "f/test/simple_script.ts",
+        `export function main(name: string = "World") {
+  return \`Hello, \${name}!\`;
+}`
+      );
+
+      const result = await backend.runCLICommand(
+        ["script", "preview", "f/test/simple_script.ts"],
+        tempDir
+      );
+
+      assertEquals(result.code, 0, `Preview failed: ${result.stderr}\n${result.stdout}`);
+      assertStringIncludes(result.stdout + result.stderr, "Hello, World!");
+    });
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name: "script preview: codebase script (CJS)",
+  async fn() {
+    await withTestBackend(async (backend, tempDir) => {
+      await createWmillConfig(tempDir, {
+        defaultTs: "bun",
+        codebases: [{ relative_path: "f/codebase", includes: ["**"] }],
+      });
+
+      await createScript(
+        tempDir,
+        "f/codebase/cjs_script.ts",
+        `export function main(name: string = "World") {
+  console.log("CJS codebase script running");
+  return \`Hello from CJS codebase, \${name}!\`;
+}`
+      );
+
+      const result = await backend.runCLICommand(
+        ["script", "preview", "f/codebase/cjs_script.ts"],
+        tempDir
+      );
+
+      assertEquals(result.code, 0, `Preview failed: ${result.stderr}\n${result.stdout}`);
+      assertStringIncludes(result.stdout + result.stderr, "Hello from CJS codebase, World!");
+    });
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name: "script preview: codebase script (ESM)",
+  async fn() {
+    await withTestBackend(async (backend, tempDir) => {
+      await createWmillConfig(tempDir, {
+        defaultTs: "bun",
+        codebases: [{ relative_path: "f/codebase_esm", includes: ["**"], format: "esm" }],
+      });
+
+      await createScript(
+        tempDir,
+        "f/codebase_esm/esm_script.ts",
+        `export function main(name: string = "World") {
+  console.log("ESM codebase script running");
+  return \`Hello from ESM codebase, \${name}!\`;
+}`
+      );
+
+      const result = await backend.runCLICommand(
+        ["script", "preview", "f/codebase_esm/esm_script.ts"],
+        tempDir
+      );
+
+      assertEquals(result.code, 0, `Preview failed: ${result.stderr}\n${result.stdout}`);
+      assertStringIncludes(result.stdout + result.stderr, "Hello from ESM codebase, World!");
+    });
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name: "script preview: codebase script with assets (tar)",
+  async fn() {
+    await withTestBackend(async (backend, tempDir) => {
+      await createWmillConfig(tempDir, {
+        defaultTs: "bun",
+        codebases: [{
+          relative_path: "f/codebase_tar",
+          includes: ["**"],
+          assets: [{ from: "f/codebase_tar/data.json", to: "data.json" }],
+        }],
+      });
+
+      // Create asset file
+      await Deno.mkdir(`${tempDir}/f/codebase_tar`, { recursive: true });
+      await Deno.writeTextFile(
+        `${tempDir}/f/codebase_tar/data.json`,
+        JSON.stringify({ message: "Hello from asset!" })
+      );
+
+      await createScript(
+        tempDir,
+        "f/codebase_tar/tar_script.ts",
+        `import * as fs from "fs";
+
+export function main(name: string = "World") {
+  console.log("Tar codebase script running");
+  const data = fs.readFileSync("data.json", "utf-8");
+  const parsed = JSON.parse(data);
+  return \`Hello \${name}! Asset says: \${parsed.message}\`;
+}`
+      );
+
+      const result = await backend.runCLICommand(
+        ["script", "preview", "f/codebase_tar/tar_script.ts"],
+        tempDir
+      );
+
+      assertEquals(result.code, 0, `Preview failed: ${result.stderr}\n${result.stdout}`);
+      assertStringIncludes(result.stdout + result.stderr, "Hello World! Asset says: Hello from asset!");
+    });
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name: "script preview: codebase script ESM + tar (assets)",
+  async fn() {
+    await withTestBackend(async (backend, tempDir) => {
+      await createWmillConfig(tempDir, {
+        defaultTs: "bun",
+        codebases: [{
+          relative_path: "f/codebase_esm_tar",
+          includes: ["**"],
+          format: "esm",
+          assets: [{ from: "f/codebase_esm_tar/config.json", to: "config.json" }],
+        }],
+      });
+
+      // Create asset file
+      await Deno.mkdir(`${tempDir}/f/codebase_esm_tar`, { recursive: true });
+      await Deno.writeTextFile(
+        `${tempDir}/f/codebase_esm_tar/config.json`,
+        JSON.stringify({ setting: "esm_tar_value" })
+      );
+
+      await createScript(
+        tempDir,
+        "f/codebase_esm_tar/esm_tar_script.ts",
+        `import * as fs from "fs";
+
+export function main(name: string = "World") {
+  console.log("ESM + tar codebase script running");
+  const config = fs.readFileSync("config.json", "utf-8");
+  const parsed = JSON.parse(config);
+  return \`Hello \${name}! Config setting: \${parsed.setting}\`;
+}`
+      );
+
+      const result = await backend.runCLICommand(
+        ["script", "preview", "f/codebase_esm_tar/esm_tar_script.ts"],
+        tempDir
+      );
+
+      assertEquals(result.code, 0, `Preview failed: ${result.stderr}\n${result.stdout}`);
+      assertStringIncludes(result.stdout + result.stderr, "Hello World! Config setting: esm_tar_value");
+    });
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+// =============================================================================
+// FLOW PREVIEW TESTS
+// =============================================================================
+
+Deno.test({
+  name: "flow preview: simple flow",
+  async fn() {
+    await withTestBackend(async (backend, tempDir) => {
+      await createWmillConfig(tempDir, { defaultTs: "bun" });
+      await createFlow(tempDir, "f/test/simple_flow.flow", {
+        summary: "Test flow",
+        scriptContent: `export function main(name: string = "World") { return \`Flow says: Hello, \${name}!\`; }`,
+      });
+
+      const result = await backend.runCLICommand(
+        ["flow", "preview", "f/test/simple_flow.flow"],
+        tempDir
+      );
+
+      assertEquals(result.code, 0, `Flow preview failed: ${result.stderr}\n${result.stdout}`);
+      assertStringIncludes(result.stdout + result.stderr, "Flow says: Hello, World!");
+    });
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+// =============================================================================
+// CLEANUP
+// =============================================================================
+
+Deno.test({
+  name: "cleanup test backend",
+  async fn() {
+    await cleanupTestBackend();
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});