fix: add dry-run feature flag for edge-function tarball generation (#6712)

Author: JakeChampion

packages/edge-bundler/node/bridge.ts

@@ -71,7 +71,9 @@ export class DenoBridge {
     this.useGlobal = options.useGlobal ?? true
 
     const useNextDeno =
-      options.featureFlags?.edge_bundler_generate_tarball || options.featureFlags?.edge_bundler_deno_v2
+      options.featureFlags?.edge_bundler_dry_run_generate_tarball ||
+      options.featureFlags?.edge_bundler_generate_tarball ||
+      options.featureFlags?.edge_bundler_deno_v2
 
     this.versionRange = options.versionRange ?? (useNextDeno ? NEXT_DENO_VERSION_RANGE : DENO_VERSION_RANGE)
   }

packages/edge-bundler/node/bundler.test.ts

@@ -828,6 +828,82 @@ describe.skipIf(lt(denoVersion, '2.4.3'))(
       await cleanup()
       await rm(vendorDirectory.path, { force: true, recursive: true })
     })
+
+    describe('Dry-run tarball generation flag enabled', () => {
+      test('Logs success message when tarball generation succeeded', async () => {
+        const systemLogger = vi.fn()
+        const { basePath, cleanup, distPath } = await useFixture('imports_node_builtin', { copyDirectory: true })
+        const declarations: Declaration[] = [
+          {
+            function: 'func1',
+            path: '/func1',
+          },
+        ]
+
+        await bundle([join(basePath, 'netlify/edge-functions')], distPath, declarations, {
+          basePath,
+          configPath: join(basePath, '.netlify/edge-functions/config.json'),
+          featureFlags: {
+            edge_bundler_dry_run_generate_tarball: true,
+            edge_bundler_generate_tarball: false,
+          },
+          systemLogger,
+        })
+
+        expect(systemLogger).toHaveBeenCalledWith('Dry run: Tarball bundle generated successfully.')
+
+        const manifestFile = await readFile(resolve(distPath, 'manifest.json'), 'utf8')
+        const manifest = JSON.parse(manifestFile)
+
+        expect(manifest.bundles.length).toBe(1)
+        expect(manifest.bundles[0].format).toBe('eszip2')
+
+        await cleanup()
+      })
+
+      test('Logs error message when tarball generation failed and does not fail the overall build', async () => {
+        const systemLogger = vi.fn()
+        vi.resetModules()
+        vi.doMock('./formats/tarball.js', () => ({
+          bundle: vi.fn().mockRejectedValue(new Error('Simulated tarball bundling failure')),
+        }))
+
+        const { bundle: bundleUnderTest } = await import('./bundler.js')
+
+        const { basePath, cleanup, distPath } = await useFixture('imports_node_builtin', { copyDirectory: true })
+        const sourceDirectory = join(basePath, 'functions')
+        const declarations: Declaration[] = [
+          {
+            function: 'func1',
+            path: '/func1',
+          },
+        ]
+
+        await expect(
+          bundleUnderTest([sourceDirectory], distPath, declarations, {
+            basePath,
+            configPath: join(sourceDirectory, 'config.json'),
+            featureFlags: {
+              edge_bundler_dry_run_generate_tarball: true,
+              edge_bundler_generate_tarball: false,
+            },
+            systemLogger,
+          }),
+        ).resolves.toBeDefined()
+
+        expect(systemLogger).toHaveBeenCalledWith(
+          `Dry run: Tarball bundle generation failed: Simulated tarball bundling failure`,
+        )
+
+        const manifestFile = await readFile(resolve(distPath, 'manifest.json'), 'utf8')
+        const manifest = JSON.parse(manifestFile)
+        expect(manifest.bundles.length).toBe(1)
+        expect(manifest.bundles[0].format).toBe('eszip2')
+
+        await cleanup()
+        vi.resetModules()
+      })
+    })
   },
   10_000,
 )

packages/edge-bundler/node/bundler.ts

@@ -119,20 +119,35 @@ export const bundle = async (
 
   const bundles: Bundle[] = []
 
-  if (featureFlags.edge_bundler_generate_tarball) {
-    bundles.push(
-      await bundleTarball({
-        basePath,
-        buildID,
-        debug,
-        deno,
-        distDirectory,
-        functions,
-        featureFlags,
-        importMap: importMap.clone(),
-        vendorDirectory: vendor?.directory,
-      }),
-    )
+  if (featureFlags.edge_bundler_generate_tarball || featureFlags.edge_bundler_dry_run_generate_tarball) {
+    const tarballPromise = bundleTarball({
+      basePath,
+      buildID,
+      debug,
+      deno,
+      distDirectory,
+      functions,
+      featureFlags,
+      importMap: importMap.clone(),
+      vendorDirectory: vendor?.directory,
+    })
+
+    if (featureFlags.edge_bundler_dry_run_generate_tarball) {
+      try {
+        await tarballPromise
+        logger.system('Dry run: Tarball bundle generated successfully.')
+      } catch (error: unknown) {
+        if (error instanceof Error) {
+          logger.system(`Dry run: Tarball bundle generation failed: ${error.message}`)
+        } else {
+          logger.system(`Dry run: Tarball bundle generation failed: ${String(error)}`)
+        }
+      }
+    }
+
+    if (featureFlags.edge_bundler_generate_tarball) {
+      bundles.push(await tarballPromise)
+    }
   }
 
   if (vendor) {

packages/edge-bundler/node/feature_flags.ts

@@ -1,5 +1,6 @@
 const defaultFlags = {
   edge_bundler_generate_tarball: false,
+  edge_bundler_dry_run_generate_tarball: false,
   edge_bundler_deno_v2: false,
 }