[APPS] Minify backend bundles

[ksun154]

What and why?

Follow-up to the pitchGPT HTTP 413 ("bundle exceeds the maximum decompressed size of 52 MB"). The server's limit is maxBundleSize = 50 * 1024 * 1024 (50 MiB) in app-builder-code's internal/uploader/bundle_storage.go; "52 MB" is that value printed in decimal units by humanize.Bytes. It complements #538, which enables tree-shaking. The two are independent and can merge in either order.

• Production backend bundles are now minified with esbuild, using keepNames: true. Minification is always on; there's no public option.
• Every package build logs its file count, compressed size and decompressed size. Today a 413 is the first anyone hears about bundle size; the log line makes the number visible on every build.

This takes the minification and the size reporting from #533. It leaves out #533's apps.backend.minify opt-out and its near-limit warning: the warning would hardcode a client-side copy of the server's limit, which drifts (#533's 52 MB was already the server's 50 MiB maxBundleSize printed in decimal units).

How?

• vite/build-backend-functions.ts: sets minify: 'esbuild' and esbuild: { keepNames: true } only in the production vite.build() call. The shared getBaseBackendBuildConfig is unchanged, so the dev-server bundles sent to preview-async stay unminified.
• archive.ts: Archive gains decompressedSize, the sum of the packaged files' sizes. The server's 50 MiB limit counts this total (frontend/, backend/*.js and manifest.json), not the zip size.
• vite/build-package.ts: logs App package size: N files, X MB compressed, Y MB decompressed.

Measurements

Total backend JS on master's config (no tree-shaking), minification toggled:

	minify: false	This PR
Synthetic app: 13 functions in 3 files (zod, lodash-es, date-fns, yaml, apps-backend)	15.86 MB	3.18 MB (−80%)

Combined with #538's tree-shaking, measured on the same app (minify with keepNames, against tree-shaking alone):

	Tree-shake only	+ minify keepNames	+ minify, no keepNames
Repo fixture (apps_backend_project, 7 functions)	71,271 B	42,111 B (−41%)	39,916 B
Synthetic app	4.44 MB	1.74 MB (−61%)	1.65 MB

The synthetic app is not pitchGPT. Code-heavy dependencies minify well; data- or string-heavy ones (locale tables, JSON) much less. pitchGPT has not been measured yet.

Follow-ups

• Confirm whether Terrapin or function logs can apply source maps, which nobody has confirmed yet, and where the maps would be stored.
• a near-limit warning, ideally in @datadog/apps-cli with the limit read from the API instead of hardcoded. The CLI would also cover uploading an existing zip, which the plugin never sees.

[datadog-datadog-prod-us1]

✅ All CI checks and tests passed.

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 63bb070 | Docs | View more details | Give us feedback!}

[Copilot]

Copilot review overview

🟢 Approval recommended

The behavior is well-scoped and covered by targeted tests, with only minor non-blocking convention feedback.

Review effort: Balanced
Findings: 2

Open (2)

• Use the existing filesystem helper instead of importing fs directly · New
• Replace type assertion with a runtime Error guard · New

What changed in this PR

Minifies production backend bundles while adding archive-size reporting and warnings near the upload limit.

Changes:

• Enables esbuild minification while preserving function and class names.
• Tracks and logs compressed/decompressed package sizes.
• Warns when decompressed size reaches 90% of 52 MB and adds regression coverage.

File	Description
packages/​plugins/​apps/​src/​archive.ts	Calculates decompressed archive size.
packages/​plugins/​apps/​src/​constants.ts	Defines size limit and warning ratio.
packages/​plugins/​apps/​src/​vite/​build-package.ts	Logs package sizes and emits warnings.
packages/​plugins/​apps/​src/​vite/​build-backend-functions.ts	Minifies production backend bundles.
packages/​plugins/​apps/​src/​vite/​build-backend-functions.test.ts	Tests minification and preserved names.
packages/​plugins/​apps/​src/​index.test.ts	Tests size reporting and warning boundaries.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation is focused and well tested; only a non-blocking stale comment needs correction.

Review effort: Balanced
Findings: 1

Open (1)

• Remove stale decompressed-size warning reference · New

Resolved since last review (2)

• Replace type assertion with a runtime Error guard
• Use the existing filesystem helper instead of importing fs directly