From 4a8884f03dc08ecf5be9bc6872b450fc5f5cbcf0 Mon Sep 17 00:00:00 2001
From: Alfonso Noriega <alfonso.noriega@shopify.com>
Date: Thu, 9 Apr 2026 22:56:55 +0200
Subject: [PATCH] fix: copy raw binary to dist/index.wasm during standalone
 builds, not base64

---
 .../src/cli/services/build/extension.test.ts  | 36 ++++++++++++++++---
 .../app/src/cli/services/build/extension.ts   | 19 ++++++----
 2 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/packages/app/src/cli/services/build/extension.test.ts b/packages/app/src/cli/services/build/extension.test.ts
index 7f4be98556..9fe8052cf6 100644
--- a/packages/app/src/cli/services/build/extension.test.ts
+++ b/packages/app/src/cli/services/build/extension.test.ts
@@ -7,7 +7,7 @@ import {beforeEach, describe, expect, test, vi} from 'vitest'
 import {exec} from '@shopify/cli-kit/node/system'
 import lockfile from 'proper-lockfile'
 import {AbortError} from '@shopify/cli-kit/node/error'
-import {fileExistsSync, touchFile, writeFile} from '@shopify/cli-kit/node/fs'
+import {copyFile, fileExistsSync, touchFile, writeFile} from '@shopify/cli-kit/node/fs'
 import {joinPath} from '@shopify/cli-kit/node/path'
 
 vi.mock('@shopify/cli-kit/node/system')
@@ -418,7 +418,32 @@ describe('buildFunctionExtension', () => {
     expect(runWasmOpt).toHaveBeenCalled()
   })
 
-  test('does not rebundle when build.path stays in the default output directory', async () => {
+  test('copies raw binary (not base64) to dist/index.wasm when build.path is in a different dir (standalone build)', async () => {
+    // Given
+    extension.configuration.build!.path = 'target/wasm32-wasi/release/my_func.wasm'
+    vi.mocked(fileExistsSync).mockReturnValue(true)
+
+    // When
+    await expect(
+      buildFunctionExtension(extension, {
+        stdout,
+        stderr,
+        signal,
+        app,
+        environment: 'production',
+      }),
+    ).resolves.toBeUndefined()
+
+    // Then: copyFile is used (raw binary copy), NOT base64 bundling via touchFile/writeFile
+    expect(copyFile).toHaveBeenCalledWith(
+      joinPath(extension.directory, 'target/wasm32-wasi/release/my_func.wasm'),
+      joinPath(extension.directory, 'dist', 'index.wasm'),
+    )
+    expect(touchFile).not.toHaveBeenCalled()
+    expect(writeFile).not.toHaveBeenCalled()
+  })
+
+  test('copies raw binary to dist/index.wasm when build.path stays in the default output directory', async () => {
     // Given
     extension.configuration.build!.path = 'dist/custom.wasm'
     vi.mocked(fileExistsSync).mockReturnValue(true)
@@ -434,8 +459,11 @@ describe('buildFunctionExtension', () => {
       }),
     ).resolves.toBeUndefined()
 
-    // Then
-    expect(fileExistsSync).toHaveBeenCalledWith(joinPath(extension.directory, 'dist/custom.wasm'))
+    // Then: copyFile is used (raw binary copy), NOT base64 bundling via touchFile/writeFile
+    expect(copyFile).toHaveBeenCalledWith(
+      joinPath(extension.directory, 'dist/custom.wasm'),
+      joinPath(extension.directory, 'dist', 'index.wasm'),
+    )
     expect(touchFile).not.toHaveBeenCalled()
     expect(writeFile).not.toHaveBeenCalled()
   })
diff --git a/packages/app/src/cli/services/build/extension.ts b/packages/app/src/cli/services/build/extension.ts
index 97e8eca8f7..155ddbdaf6 100644
--- a/packages/app/src/cli/services/build/extension.ts
+++ b/packages/app/src/cli/services/build/extension.ts
@@ -10,7 +10,7 @@ import {AbortError, AbortSilentError} from '@shopify/cli-kit/node/error'
 import lockfile from 'proper-lockfile'
 import {dirname, joinPath} from '@shopify/cli-kit/node/path'
 import {outputDebug} from '@shopify/cli-kit/node/output'
-import {readFile, touchFile, writeFile, fileExistsSync} from '@shopify/cli-kit/node/fs'
+import {copyFile, readFile, touchFile, writeFile, fileExistsSync} from '@shopify/cli-kit/node/fs'
 import {Writable} from 'stream'
 
 export interface ExtensionBuildOptions {
@@ -161,12 +161,17 @@ export async function buildFunctionExtension(
       await runTrampoline(extension.outputPath)
     }
 
-    if (
-      fileExistsSync(extension.outputPath) &&
-      bundlePath !== extension.outputPath &&
-      dirname(bundlePath) !== dirname(extension.outputPath)
-    ) {
-      await bundleFunctionExtension(extension.outputPath, bundlePath)
+    if (fileExistsSync(extension.outputPath) && bundlePath !== extension.outputPath) {
+      const projectOutputPath = joinPath(extension.directory, extension.outputRelativePath)
+      if (bundlePath === projectOutputPath) {
+        // Standalone build (e.g. `shopify app build`): copy raw binary to dist/index.wasm so
+        // vitest and other local tooling can load the wasm directly.
+        await copyFile(extension.outputPath, bundlePath)
+      } else if (dirname(bundlePath) !== dirname(extension.outputPath)) {
+        // Bundle build for deploy: base64-encode into the bundle directory to satisfy the
+        // server-side contract of uploaded_files["dist/index.wasm"].
+        await bundleFunctionExtension(extension.outputPath, bundlePath)
+      }
     }
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
   } catch (error: any) {