feat(typescript): add naming configuration object for independent control of class/type names

[Swimburger]

Description

Refs: Requested by @Swimburger
Link to Devin Session: https://app.devin.ai/sessions/4ba47fb86534412697f8c6063795cd0c

Adds a new naming configuration to the TypeScript SDK generator that allows users to independently control the namespace export and PascalCase class/type names (client, error, timeout error, environment, environment URLs, version). The existing namespaceExport config continues to work for backwards compatibility.

Supports both a string shorthand and a full object form:

# String shorthand — derives all names via PascalCase
config:
  naming: acme
# Produces: namespace=acme, AcmeClient, AcmeError, AcmeTimeoutError, etc.

# Object form — override individual names
config:
  naming:
    namespace: acme
    client: AcmeSdkClient
    error: AcmeApiError
    environment: AcmeApiEnvironment

When individual overrides are not provided, they are derived from PascalCase(namespace) + suffix (e.g., namespace: "acme" → AcmeClient, AcmeError, etc.). When no naming config is present at all, namespaceExport is used as-is for suffix derivation, preserving backwards compatibility (e.g., namespaceExport: "MySDK" → MySDKClient).

Changes Made

• Added NamingConfigSchema to TypescriptCustomConfigSchema.ts as a z.union([string, object]) with 7 optional string fields
• Added JS identifier validation on naming.namespace and the string shorthand form (rejects invalid identifiers like my-api)
• Added NamingConfig type (string | NamingObjectConfig) and naming field to SdkCustomConfig
• Updated getNamespaceExport() to accept naming (string or object) with priority: naming.namespace (or string value) > namespaceExport > default
• Added resolveNaming() utility that resolves all naming overrides with conditionally PascalCased defaults (PascalCase when naming config is explicitly provided; raw namespaceExport otherwise for backwards compatibility)
• Updated SdkGeneratorCli to resolve naming and pass it through to SdkGenerator
• Updated all declaration referencers to use namingOverride ?? <default> pattern:
  • SdkRootClientClassDeclarationReferencer (client name)
  • GenericAPISdkErrorDeclarationReferencer (error name)
  • TimeoutSdkErrorDeclarationReferencer (timeout error name)
  • EnvironmentsDeclarationReferencer (environment + environment URLs names)
  • VersionDeclarationReferencer (version name)
• Updated DynamicSnippetsGeneratorContext to use resolved client and environment names
• Added seed test fixture simple-api/naming with unique, non-inferable names to verify each override is applied independently
• Added seed test fixture simple-api/naming-shorthand using string shorthand naming: acme to verify PascalCase default derivation
• Added v3.56.0 changelog entry

Review Checklist

• ResolvedNaming interface is duplicated in SdkGenerator.ts and getNamespaceExport.ts — SdkGenerator package lacks a dependency on @fern-api/typescript-browser-compatible-base, so importing would require adding a new dep for a 7-field interface. Duplication is intentional.
• namingOverride is passed to SdkClientClassDeclarationReferencer which forwards it to both root and subpackage referencers — verified subpackage client correctly ignores it (derives from subpackage.name.pascalCase.unsafeName, not root naming).
• An empty naming: {} object (no fields set) triggers PascalCase derivation because naming != null is true — confirmed acceptable behavior.
• Added naming-shorthand fixture exercising the default derivation path (naming: acme without explicit overrides).
• naming.namespace and string shorthand are validated as valid JS identifiers via Zod .refine() (rejects my-api, etc.).

Items for human reviewer attention

• The jsIdentifier Zod .refine() changes the inferred type — verify downstream consumers handle this correctly (string fields that pass through the refinement).
• The string shorthand naming: "acme" normalizes to {} in resolveNaming, which triggers PascalCase derivation via naming != null. Confirm this is the desired behavior for all edge cases.

Testing

• Lint checks pass (pnpm run check)
• Seed test fixtures added and generated output committed (simple-api/naming + simple-api/naming-shorthand)
• All 19 simple-api seed tests pass locally (including both new fixtures)
• Existing tests unaffected (backwards compatible — all naming overrides are optional)

---

[devin-ai-integration]

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[Swimburger]

Can you actually give unique names for each so we can verify none of them are accidentally inferred. Also don't use xai, our prospect, directly in the code

[devin-ai-integration]

Updated the fixture to use unique, non-inferable names so we can verify none are accidentally derived:

naming:
  namespace: acme
  client: AcmeSdkClient
  error: AcmeApiError
  timeoutError: AcmeRequestTimeoutError
  environment: AcmeApiEnvironment
  environmentUrls: AcmeApiEnvironmentUrls
  version: AcmeApiVersion

Each name is distinct and wouldn't match what PascalCase derivation would produce (e.g., AcmeSdkClient vs default AcmeClient, AcmeApiError vs default AcmeError, AcmeRequestTimeoutError vs default AcmeTimeoutError).

[Swimburger]

now, allow naming: acme, and derive everything from the shorthand.

[devin-ai-integration]

Done! String shorthand naming: acme is now supported and derives all names via PascalCase:

naming: acme

Produces: AcmeClient, AcmeError, AcmeTimeoutError, AcmeEnvironment, AcmeEnvironmentUrls, AcmeVersion with namespace export acme.

Also added:

• A naming-shorthand seed fixture exercising the default derivation path
• JS identifier validation on naming.namespace and the string shorthand (rejects invalid identifiers like my-api)
• Updated docs to document the string shorthand form