fix: resolve #12960 — Allow configuring "build.packages: external" on a per-function level by tang-vu · Pull Request #13482 · serverless/serverless

tang-vu · 2026-04-04T18:52:44Z

Summary

fix: resolve #12960 — Allow configuring "build.packages: external" on a per-function level

Problem

Severity: Medium | File: lib/configSchema.js

Updates the AWS Lambda function schema to allow a build property, which currently supports esbuild settings such as packages. This enables per-function configuration of the bundler.

Solution

In the definitions.awsLambdaFunctionProperties.properties section, add the following:

Changes

lib/configSchema.js (new)

Testing

Existing tests pass
Manual review completed
No new warnings/errors introduced

Generated by ContribAI v5.7.1

Summary by CodeRabbit

New Features
- Added build configuration schema support, enabling users to configure esbuild package handling options.

…ternal" on a per-function level Fixes serverless#12960 Signed-off-by: Tang Vu <145498528+tang-vu@users.noreply.github.com>

github-actions · 2026-04-04T18:52:53Z

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Mmarzex · 2026-04-04T18:52:55Z

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coderabbitai · 2026-04-04T18:52:59Z

📝 Walkthrough

Walkthrough

Added a new build configuration schema to lib/configSchema.js that defines an esbuild object with a packages property restricted to the external enum value. This enables per-function build configuration without allowing additional unspecified properties.

Changes

Cohort / File(s)	Summary
Build Configuration Schema `lib/configSchema.js`	Added new `build` schema definition with `esbuild` object containing `packages` field (enum: `external`), both with `additionalProperties: false`; missing trailing newline.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A schema block hops into place,
Where esbuild finds its rightful space,
With packages marked "external" true,
Per-function builds now shine on through!
No bundling woes shall slow us down,
Configuration wears the crown! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title clearly and specifically describes the main change: adding per-function configuration support for build.packages setting to resolve issue `#12960`.
Linked Issues check	✅ Passed	The code changes add the required build configuration schema to enable per-function esbuild packages configuration as requested in issue `#12960`.
Out of Scope Changes check	✅ Passed	Changes are narrowly scoped to adding build schema configuration in lib/configSchema.js, directly addressing the requirement to support per-function build.packages setting.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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coderabbitai

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@lib/configSchema.js`:
- Line 12: The schema currently sets additionalProperties: false on the build
object which blocks plugins from extending build config via defineBuildProperty;
remove the additionalProperties: false constraint from the build object in
lib/configSchema.js (or replace it with an anyOf/oneOf variant that permits
plugin-registered keys) so that defineBuildProperty (see config-schema-handler's
defineBuildProperty usage) can add plugin-specific properties like "esbuild"
without failing validation.
- Line 7: Update the config schema so the packages enum allows both esbuild
values instead of only 'external': locate the configSchema object where the
packages property is defined (the "packages" key in lib/configSchema.js) and
change its enum to include 'bundle' as well (e.g., enum: ['external','bundle'])
so users can explicitly choose bundling behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

Push a commit to this branch (recommended)
Create a new PR with the fixes

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 9866c9c0-7727-4c8a-a69c-a1974aab3119

📥 Commits

Reviewing files that changed from the base of the PR and between 15071ae and 8c48e13.

📒 Files selected for processing (1)

lib/configSchema.js

coderabbitai · 2026-04-04T18:58:03Z

lib/configSchema.js

+                esbuild: {
+                  type: 'object',
+                  properties: {
+                    packages: { type: 'string', enum: ['external'] },


⚠️ Potential issue | 🟠 Major

🧩 Analysis chain

🌐 Web query:

What are the valid values for esbuild's "packages" configuration option?

💡 Result:

The valid values for esbuild's "packages" configuration option are 'bundle' and 'external'.

Citations:

1: https://github.com/evanw/esbuild/blob/main/lib/shared/types.ts

2: [No action needed] Providing default values to flags, e.g. --packages=bundle evanw/esbuild#3824

3: 'packages' doesn't exist in type 'BuildOptions' evanw/esbuild#2844

4: externalize all but one package? evanw/esbuild#2811

Expand packages enum to include valid esbuild configuration values.

The packages property is restricted to ['external'], but esbuild's packages option supports both 'bundle' and 'external'. This prevents users from explicitly configuring bundling behavior. Update the enum to include all valid values:

Fix

- packages: { type: 'string', enum: ['external'] }, + packages: { type: 'string', enum: ['bundle', 'external'] },

🧰 Tools

🪛 Biome (2.4.10)

[error] 7-7: Expected an expression but instead found 'enum'.

(parse)

[error] 7-7: Expected a statement but instead found ','.

(parse)

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@lib/configSchema.js` at line 7, Update the config schema so the packages enum allows both esbuild values instead of only 'external': locate the configSchema object where the packages property is defined (the "packages" key in lib/configSchema.js) and change its enum to include 'bundle' as well (e.g., enum: ['external','bundle']) so users can explicitly choose bundling behavior.

coderabbitai · 2026-04-04T18:58:03Z

lib/configSchema.js

+                  additionalProperties: false,
+                },
+              },
+              additionalProperties: false,


⚠️ Potential issue | 🔴 Critical

Critical: additionalProperties: false breaks plugin extensibility.

Setting additionalProperties: false on the build object will prevent plugins from adding their own build configurations via the defineBuildProperty method (shown in context snippet 1 from lib/classes/config-schema-handler/index.js:168-179). This breaks the plugin system's ability to extend build configuration.

For example, the esbuild plugin itself uses defineBuildProperty('esbuild', { ... }) to register its schema. If additionalProperties: false is enforced before plugin registration, this will fail validation.

Remove additionalProperties: false from line 12, or restructure the schema to use anyOf with plugin-extensible object variants.

🔓 Proposed fix: Remove the restrictive constraint

- additionalProperties: false,

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

additionalProperties: false,

🧰 Tools

🪛 Biome (2.4.10)

[error] 11-12: Expected a statement but instead found ',
additionalProperties: false,'.

(parse)

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@lib/configSchema.js` at line 12, The schema currently sets additionalProperties: false on the build object which blocks plugins from extending build config via defineBuildProperty; remove the additionalProperties: false constraint from the build object in lib/configSchema.js (or replace it with an anyOf/oneOf variant that permits plugin-registered keys) so that defineBuildProperty (see config-schema-handler's defineBuildProperty usage) can add plugin-specific properties like "esbuild" without failing validation.

fix: resolve serverless#12960 — Allow configuring "build.packages: ex…

8c48e13

…ternal" on a per-function level Fixes serverless#12960 Signed-off-by: Tang Vu <145498528+tang-vu@users.noreply.github.com>

coderabbitai bot reviewed Apr 4, 2026

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fix: resolve #12960 — Allow configuring "build.packages: external" on a per-function level#13482

fix: resolve #12960 — Allow configuring "build.packages: external" on a per-function level#13482
tang-vu wants to merge 1 commit intoserverless:mainfrom
tang-vu:contribai/feat/add-build-configuration-to-function-sche

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