[eas-build-job] Accept legacy command/path custom function shape in function.yml

[sswrk]

Why

We want to grandfather the legacy reusable functions from custom builds (https://docs.expo.dev/custom-builds/functions/) into the new reusable functions that can be used in workflows. This is to make the migration from custom builds to workflows easier.

Currently, we only support composite functions. The first step towards extending the support is modifying the eas-build-job Zod schema.

How

• Added the legacyFunction module with Zod schemas to match the legacy custom builds functions.
  • Two separate schemas: LegacyCommandFunctionConfigZ (functions with command: present) and LegacyPathFunctionConfigZ (functions with path: present).
• Extracted compositeFunction and created a new localFunction module with schema that is a union of composite function schema and legacy function schemas.

Test Plan

Added unit tests.

[linear-code]

ENG-25402

[sswrk]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [eas-cli] Validate legacy command/path local functions referenced from workflows #4098
• [build-tools] Load legacy command/path local functions and resolve module paths #4097
• [steps] Expand legacy command/path local functions to a single build step #4096
• [eas-build-job] Accept legacy command/path custom function shape in function.yml #4095 👈 (View in Graphite)
• [eas-cli][build-tools][steps] Validate local composite functions referenced from workflow hooks; extract the shared loader into steps #4064
• [build-tools][steps] Load composite function catalogs for hook steps #4063
• [steps] Support local composite functions in hook steps #4062
• [steps] Unify the default gating of steps with no if: across steps, composite scopes, and hooks #4061
• [eas-cli] Validate local composite functions in workflow files #3931
• [build-tools] Load local composite function catalog at build runtime #3930
• [steps][4/4] Resolve composite function outputs #4015
• [steps][3/4] Interpolate composite function inputs #4014
• [steps][2/4] Expand composite function references into build steps #3929 : 1 other dependent PR (#4013 )
• [steps][1/4] Add isCompositeFunctionPath and reject local composite functions in custom builds #3956
• [eas-build-job] Add local composite function schema #3928
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[github-actions]

⏩ The changelog entry check has been skipped since the "no changelog" label is present.

[github-actions]

🤖 AI code review

Decision: Approve

Overall PR risk: Medium. The change modifies existing behavior in local function config parsing and package exports. The affected surface is bounded to local function schemas, where callers can see new parse results or new rejection for mixed shapes. No specialist reviewer reported a warning or critical finding.

No findings.

---

This review is advisory — it never blocks a merge and never auto-approves.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.43%. Comparing base (81eb14f) to head (ef13e90).

Additional details and impacted files

@@                                         Coverage Diff                                          @@
##           szymonswierk/eng-22387-eas-cli-validate-hook-composite-functions    #4095      +/-   ##
====================================================================================================
+ Coverage                                                             62.42%   62.43%   +0.02%     
====================================================================================================
  Files                                                                  1008     1010       +2     
  Lines                                                                 45712    45728      +16     
  Branches                                                               9622     9622              
====================================================================================================
+ Hits                                                                  28530    28546      +16     
  Misses                                                                15721    15721              
  Partials                                                               1461     1461              

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