fix(cli, typescript): Fix package.json metadata loss during local generation

[devin-ai-integration]

Description

Refs: Customer issue (Payabli)

Fixes an issue where package.json metadata (name, version, repository, private) was being lost during local TypeScript SDK generation when using non-self-hosted GitHub configuration with npm output. The customer's SDK went from having proper metadata to only having "name": "test-package".

Link to Devin run: https://app.devin.ai/sessions/18a5ef103b3e4a71a5a433cba9770f81
Requested by: Niels Swimberghe (@Swimburger)

Changes Made

• Added a new code path in getPublishConfig to create a filesystem publishConfig with the publish target when a non-self-hosted github config has output info
• Updated AbstractGeneratorCli.ts to fall back to publishConfig when constructNpmPackage returns undefined (e.g., in downloadFiles mode)
• Extracted npmPackageInfoFromPublishConfig to its own module for better testability
• Added handling for all three publishConfig types (github, direct, filesystem) in npmPackageInfoFromPublishConfig
• Updated versions.yml for TypeScript SDK (3.39.3)

Root Cause

When running local generation (fern generate without mode flags), the output mode is downloadFiles. The getPublishConfig function was returning undefined for non-self-hosted github configs, even when they had output info with npm package details. This caused ir.publishConfig to be undefined, and the generator fell back to name: "test-package".

Updates Since Last Revision

• Added comprehensive unit tests for npmPackageInfoFromPublishConfig covering:
  • GitHub publishConfig with npm target (including owner/repo and uri fallback)
  • Filesystem publishConfig with npm publishTarget
  • Direct publishConfig with npm target
  • Non-npm publish targets (maven, pypi)
  • Undefined publishConfig handling
  • License config preservation
  • isPackagePrivate flag handling
• Refactored npmPackageInfoFromPublishConfig into its own file for better modularity
• Fixed TypeScript compilation errors in tests (removed branch property not present in npm package version of @fern-fern/ir-sdk)

Human Review Checklist

• Verify the fallback logic in AbstractGeneratorCli.ts for self-hosted IR scenarios (now falls back to constructNpmPackage if constructNpmPackageFromArgs returns undefined)
• Check if the new code path in getPublishConfig handles edge cases correctly (e.g., what if github is set but output is not npm?)
• Review the visitor pattern in getRepoUrl for handling different publishConfig types
• Note: Tests use @fern-fern/ir-sdk@^61.7.0 which lacks branch property on GithubPublish (local packages/ir-sdk has it)

Testing

• Lint checks pass (pnpm run check)
• TypeScript compilation passes (pnpm run compile)
• Unit tests added for npmPackageInfoFromPublishConfig (11 tests passing)
• Manual testing with customer's configuration

[devin-ai-integration]

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