Add field description inheritance from referenced types during introspection

[jwaldrip]

Summary

This PR enhances GraphQL introspection by making fields inherit descriptions from their referenced types when no explicit description is provided. This improves API documentation by automatically propagating type descriptions to fields that reference those types.

Motivation

Currently, when a field has no description, introspection returns null even if the field references a well-documented type. This leads to incomplete API documentation where developers must manually duplicate type descriptions on every field that references that type.

Example

object :user do
  description "A user in the system"
  field :id, :id
  field :name, :string
end

object :post do
  field :author, :user  # Currently returns null description in introspection
end

With this change, the author field will automatically inherit the description "A user in the system" during introspection.

Implementation Details

• Modified the __field introspection resolver to check if a field has no description and attempt to use the referenced type's description as a fallback
• Properly handles wrapped types (non_null, list_of) by unwrapping them first before looking up the base type
• Works with custom types, built-in scalars, interfaces, and all GraphQL type constructs

Testing

Added comprehensive test coverage in test/absinthe/introspection/field_description_inheritance_test.exs including:

• Direct type references
• Wrapped types (non_null, list_of)
• Built-in scalar types
• Interface types
• Query fields
• Nested type references

All existing tests continue to pass.

Documentation

Updated the field documentation in lib/absinthe/type/field.ex to explain the new behavior.

Breaking Changes

None. This is a backwards-compatible enhancement that only affects fields without explicit descriptions.

🤖 Generated with Claude Code

[lloyd-pinrun]

Maybe I'm misunderstanding something, but would you actually want the field author to inherit the description of the type user? It seems like you'd want to add a new description for that field, e.g.:

object :post do
  @desc "The User who authored the post"
  field :author, :user
end

I'm unsure if this would be something folks would align with tbh, because if I abstain from adding a description for the field it's because it doesn't need one, and if I found that a description was inherited from the referenced type, it'd be unexpected behavior.

A potential alternative would be to include the ability to set field :author, :user, description: :inherit to allow users to explicitly decide if that field should inherit the type's description 🤷

Another thought is that the description of the "field" is separate from the description of the "object", e.g. the latter is a generalized description of the thing and the former is specific to its use-case.